Thermal management apparatus and method

Abstract

A thermal management method comprising: operating a heat pipe in a first mode to extract thermal energy from a component of a plasma confinement device, the component being thermally coupled to the heat pipe; and operating the heat pipe in a second mode to convey thermal energy to the component.

Description

[0001] THERMAL MANAGEMENT APPARATUS AND METHOD

[0002] Field of the Invention

[0003] The present invention relates to a thermal management apparatus and method.

[0004] Background

[0005] Heat pipes are passive heat transfer devices that employ a phase transition of a working fluid to convey thermal energy from an evaporator portion to a condenser portion of the heat pipe, when subject to a temperature difference.

[0006] Broadly, there are two categories of heat pipe: those that contain a wick (mainly capillary driven but can be gravity assisted) and those that do not (i.e. , are wickless and driven by other forces, such as gravity). Examples of wick-containing heat pipes include vapour chamber and variable or constant conductance heat pipes. Examples of wickless heat pipes include thermosiphons and oscillating heat pipes.

[0007] Figure 1 is a schematic illustration of a cross section of a heat pipe 100, containing a wick 108. The heat pipe 100 includes an envelope 102, which is closed at each of its ends. The envelope comprises or defines an elongate channel 104 that sealingly contains a charge 106. The elongate channel 104 is illustrated in Figure 1 as being straight, but it will be understood that it can also be bent or curved. For a constant conductance heat pipe in use, the charge consists of a working fluid (i.e., a working liquid and the vapour of the working liquid), when in use. Below the freezing pointof the working liquid, the charge in a constant conductance heat pipe is a solid. The heat pipe also includes a wick structure 108 at the envelope through which the working liquid can travel via capillary action. Example wick structures include metallic meshes or sintered powders. The wick structure can be integral to, or separate from, the envelope.

[0008] It will be understood that the term “heat pipe” is not limited to tubular designs only; heat pipes can have other external shapes, such as planar designs that are typical of vapour chambers. In planar designs, the envelope defines or comprises a channel in the sense that the dimension of the channel (a minor dimension) in a direction between opposing

[0009] 37939900-1sides of the wick is much smaller than the dimension of the channel (a major dimension) in any direction perpendicular thereto.

[0010] Figure 2 is a schematic illustration of a plan view of an alternative heat pipe 200, absent a wick. The heat pipe is an oscillating heat pipe. The heat pipe 200 includes an envelope 202, which is closed at each of its ends. The envelope comprises or defines an elongate channel 204 that sealingly contains a charge 206. As above, in use, the charge consists of a working liquid and the vapour of the working liquid. The elongate channel may be defined by grooves carved into top and / or bottom portions of the envelope, which are aligned and joined together during assembly. The elongate channel may form a closed loop or an open loop shape.

[0011] The elongate channel 204 is sized (i.e., sufficiently narrow) that, after charging the elongate channel with the working fluid, the working fluid is separated into a plurality of spatially alternating liquid 206a and vapour “slugs” 206b. That is, each liquid slug remains serially adjacent to two vapour slugs and each vapour slug remains serially adjacent to two liquid slugs along the elongate channel. As shown, the elongate channel 204 comprises one or more serpentine or II- bends 208.

[0012] In general, for any heat pipe design, working fluid is contained and sealed within the heat pipe. As noted above, below the freezing point, the charge is a solid (i.e., the liquid-gas two-phase mixture is absent below the freezing point). At any given temperature above the freezing point of the working fluid, the working fluid consists of a mixture of its liquid and its vapour (herein “working liquid” and “working vapour”). At thermodynamic equilibrium, the internal pressure of the heat pipe is the saturation pressure of the working fluid (i.e., the working vapour pressure) at the corresponding working fluid temperature.

[0013] If the heat pipe is subject to a temperature perturbation, the fraction of working liquid and working vapour in the mixture will adjust to achieve equilibrium. For example, if the temperature of the working fluid increases, the fraction of the working fluid that is a vapour will increase, whereas, if the temperature of the working fluid decreases, the fraction of the working fluid that is a vapour will decrease. The internal pressure of the heat pipe adjusts in accordance with a saturation curve.

[0014] 37939900-1A pressure-temperature phase diagram of a typical working fluid for a heat pipe is shown in Figure 3. The y-axis is pressure; the x-axis is temperature. The boundary between the liquid and vapour phase regions (denoted in the figure by L and V, respectively) is the saturation curve.

[0015] Referring to Figure 1, if a temperature difference exists across the heat pipe 100 (e.g., there is a “hot” end and a “cold” end), working liquid is caused to vaporise at the “hot” end and caused to flow towards the “cold” end, which is at a lower temperature and pressure (see the saturation curve from Figure 3). At the “cold” end, the vapour condenses back into a liquid. As a result, thermal energy is conveyed from the “hot” to the “cold” end of the heat pipe by the latent heat carried and released by the working vapour. The working liquid is drawn back to the hot end of the heat pipe through the wick by capillary action. In thermosiphons (a type of wickless heat pipe), the heat pipe is oriented so that gravity urges the condensed working liquid back to the hot end of the heat pipe. The working liquid then vaporises at the hot end of the heat pipe and the process repeats. For this reason, the “hot end” and “cold end” of the heat pipe are often referred to as the evaporator and condenser portions of the heat pipe, respectively.

[0016] Referring to Figure 2, if a temperature difference exists across the heat pipe 200 (e.g., there is a “hot” side and a “cold” side), liquid slugs at the hot side shrink in volume due to the phase change and the pressure of their adjacent gas slugs increases. At least initially, this drives flow of the slugs through the elongate channel away from the “hot” side and to the “cold” side of the heat pipe, where condensation takes place. At the cold side, liquid slugs grow in volume at the expense of their adjacent gas slugs. After a period of time, oscillatory heat pipes are characterised by an oscillatory motion of the slugs, switching between flowing from “hot-to-cold” and then from “cold-to-hot”. This oscillatory motion conveys thermal energy from the evaporator to the condenser side of the heat pipe. The energy is transported via both latent and sensible heat.

[0017] Variable conductance heat pipes, VCHs, are also known. In variable conductance heat pipes, the heat pipe sealingly contains a charge, consisting of a non-condensable gas, NCG, in addition to the working fluid. Below the freezing point of the working fluid, the heat pipe contains the NCG and the working fluid in its solid form. In use, the NCG resides at a reservoir located at the condenser portion of the heat pipe. If the cooling rate is too large, the vapour pressure at the condenser drops and the VCH is allowed to

[0018] 37939900-1expand to reduce the size of the condenser portion and hence reduce cooling. Likewise, if the cooling rate is too small, the vapour pressure at the condenser portion increases and the VCH is compressed to increase the condenser size (up to a maximum size).

[0019] Summary of the Invention

[0020] Aspects of the present invention provide a thermal management method and apparatus, as set out by the appended set of claims.

[0021] According to a first aspect of the present invention, there is provided a thermal management method. The method comprises: operating a heat pipe in a first mode to extract thermal energy from a component of a plasma confinement device, the component being thermally coupled to the heat pipe; and operating the heat pipe in a second mode to convey thermal energy to the component.

[0022] The component may be disposed in the plasma confinement device and the heat pipe may be operated in the first mode during a presence of plasma in the plasma confinement device; and the heat pipe may be operated in the second mode during an absence of plasma from the plasma confinement device.

[0023] The heat pipe may be operated in the first mode while a temperature of, or associated with, the component is greater than or equal to a first threshold temperature; and the heat pipe may be operated in the second mode while the temperature of, or associated with, the component is less than or equal to a second threshold temperature, the second threshold temperature being less than or equal to the first threshold temperature.

[0024] The first and second threshold temperatures may be different from one another; and the heat pipe may be operated in the first mode during an absence of plasma from the plasma confinement device while the temperature of, or associated with, the component is between the first and second threshold temperatures.

[0025] The heat pipe may alternate (regularly or otherwise) between operating in the first mode and operating in the second mode.

[0026] 37939900-1The component may be disposed in the plasma confinement device and the method may further comprise: changing from operating the heat pipe in the first mode to operating the heat pipe in the second mode contemporaneously with or in response to an end of a plasma pulse in the plasma confinement device; and changing from operating the heat pipe in the second mode to operating the heat pipe in the first mode contemporaneously with or in anticipation of a start of a plasma pulse in the plasma confinement device.

[0027] Additionally or alternatively, the method may further comprise changing from operating the heat pipe in the first mode to operating the heat pipe in the second mode in response to a loss or disruption of a plasma in the plasma confinement device.

[0028] In some examples, the method further comprises: determining a temperature of, or associated with, the component; and conditional upon the temperature thus determined is being greater than or equal to a maximum allowable temperature: operating the heat pipe in the first mode to decrease the temperature of, or associated with, the component.

[0029] In some examples, the method further comprises determining a temperature of, or associated with, the component; and conditional upon the temperature thus determined being less than or equal to a minimum allowable temperature: operating the heat pipe in the second mode to increase or maintain the temperature of, or associated with, the component. In some examples, the minimum allowable temperature is in a range of 600 to 700°C. The component may comprise lithium and the minimum allowable temperature may then be greater than a liquidus temperature of the lithium-containing part of the component at operating pressure. In such an example, the method may further comprise collecting tritium released from the component while or during the or each heat pipe is operated in the second mode.

[0030] Operating the heat pipe in the first mode may comprise conveying thermal energy from the component to a heat exchanger via the heat pipe; and operating the heat pipe in the second mode may comprise conveying thermal energy from the heat exchanger to the component via the heat pipe. In some examples, the method further comprises controlling one or more operating parameters of the heat exchanger.

[0031] 37939900-1The method may further comprise, while or during operating the heat pipe in the second mode, modifying one or more operating parameters of the heat exchanger to reduce the thermal energy conveyed to the component to allow the component to passively cool.

[0032] The method may further comprise determining a temperature of, or associated with, the component; and conditional upon the temperature thus determined being greater than or equal to a maximum allowable temperature: modifying one or more operating parameters of the heat exchanger to allow the component to passively cool.

[0033] The one or more operating parameters may include any one or more of: a temperature of a coolant or heat exchange fluid in the heat exchanger; a flow rate of a coolant or heat exchange fluid through the heat exchanger; and a pressure of a coolant or heat exchange fluid in the heat exchanger.

[0034] Determining a temperature of, or associated with, the component, may comprise determining a spatial distribution of temperatures across the component; and selecting a temperature from said distribution.

[0035] In some examples, the heat pipe is one of a plurality of heat pipes, each of the heat pipes being affixed to the component at a corresponding attachment portion of the component, and wherein: operating the heat pipe in the first mode comprises operating two or more of the heat pipes of the plurality in the first mode; and operating the heat pipes in the second mode comprises operating two or more of the heat pipes of the plurality in the second mode. The heat pipes of the plurality may be arranged to form an array, the array spanning across the component. In some examples, each heat pipe of the plurality alternates (regularly or otherwise) between operating in the first mode and operating in the second mode. In some examples, each heat pipe of the plurality alternates (regularly or otherwise) between the first and second operating modes contemporaneously with respect to each other heat pipe of the plurality.

[0036] In some examples, each heat pipe of the plurality is operatively coupled to a heat exchanger, and wherein: operating each heat pipe in the first mode comprises conveying thermal energy from the component to the heat exchanger via said heat pipe; and operating each heat pipe in the second mode comprises conveying thermal energy from the heat exchanger to the component via said heat pipe.

[0037] 37939900-1In some examples, each heat pipe of the plurality is operatively coupled to at least one of a plurality of heat exchangers, and wherein: operating each heat pipe in the first mode comprises conveying thermal energy from the component to at least one of the heat exchangers via said heat pipe; and operating each heat pipe in the second mode comprises conveying thermal energy from said at least one heat exchanger to the component via said heat pipe.

[0038] A melting point of the component, at 0.1 MPa, may be greater than 1100°C.

[0039] A main constituent of a material of the component may be a metallic element, the metallic element may have an atomic number greater than or equal to 40.

[0040] The component may comprise a refractory metal, such as tungsten, or an alloy of a refractory metal, such as a tungsten alloy.

[0041] In the first mode, the or each heat pipe may be operated at temperatures in excess of 200°C.

[0042] In some examples, the component is or has a castellated armour. The component may comprise a plurality of physically distinct units, optionally with said units being arranged to form a castellated structure.

[0043] The or each heat pipe may have a working fluid comprising: water, or, any one of lithium, sodium, potassium, a sodium-potassium alloy, caesium, or any mixture of the foregoing metals.

[0044] The component may be any of: a shielding layer of the plasma confinement device; a plasma facing component; a divertor; a limiter; a first wall component; a breeder blanket; a portion thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

[0045] The plasma confinement device may be any of: a magnetic confinement device; a tokamak; a stellarator; a spheromak; a spherical tokamak; a magnetic mirror machine; a reversed field pinch device; a Z-machine; a Z-pinch device; a theta-pinch device; a screw pinch device; a fusor; or a polywell.

[0046] 37939900-1The coolant (or heat exchange fluid) through the or each heat exchanger may comprise one or more of: water, a molten metal, a molten salt, an inert gas, or carbon dioxide.

[0047] In some examples, the component is disposed in the plasma confinement device and the method further comprises: operating the plasma confinement device in a pulsed or cyclic mode, wherein plasma is, by turns, present in and absent from the plasma confinement device (e.g., cycles between being present in and absent from the plasma confinement device); during a presence of plasma in the plasma confinement device, operating the heat pipe in the first mode; and during an absence of plasma from the plasma confinement device, switching from operating the heat pipe in the first mode to operating the heat pipe in the second mode.

[0048] According a second aspect of the present invention, there is provided an apparatus. The apparatus comprises: one or more heat pipes; a component to which the or each heat pipe is thermally coupled; one or more heat exchangers operatively coupled to the one or more heat pipes; and a controller coupled to the or each heat exchanger and being operable to cause the apparatus to perform the method according to the first aspect.

[0049] Brief description of the Drawings

[0050] Figures 1 and 2 are schematic illustrations of a heat pipe.

[0051] Figure 3 is a pressure-temperature phase diagram for a working fluid for a heat pipe. Figure 4 is a schematic illustration of a plasma confinement device in cross-section. Figures 5 and 6 are schematic illustrations of a divertor with a thermal management apparatus.

[0052] Figure 7A to 7C is a schematic illustration of a portion of the thermal management apparatus shown in Figure 5.

[0053] Figure 8 is a method flow diagram.

[0054] Figure 9A is a schematic illustration of a thermal management apparatus in crosssection. Figure 9B is a perspective view of the thermal management apparatus.

[0055] Figure 10 is a schematic illustration of a thermal management apparatus in crosssection.

[0056] Figure 11 is a schematic illustration of a thermal management apparatus in crosssection.

[0057] 37939900-1Figure 12A to 12B are schematic illustrations of a thermal management apparatus in plan view.

[0058] Figure 13 is a schematic illustration of a thermal management apparatus in crosssection.

[0059] Figures 14A, 14B and 14C are schematic illustrations, showing a heat pipe and component.

[0060] Figures 15A to 15D are schematic illustrations, showing a heat exchangerand heat pipe. Figures 16A to 16C are schematic illustrations of a thermal management apparatus in plan view.

[0061] Figure 17A is a schematic illustration of a heat exchanger in plan view, within which a plurality of heat pipes are arranged.

[0062] Figure 17B is a perspective view of a plurality of heat pipes.

[0063] Figure 18 is a schematic illustration of a power generation system.

[0064] Figure 19 is a method flow diagram.

[0065] Detailed description

[0066] In some engineering scenarios, it is desirable to maintain a component of a system at an elevated temperature close to its operating temperature (rather than letting it cool to ambient temperature), when the component is transiently not in use. This avoids, for example, having to ramp up the temperature of the component before recommencing operations. It can also reduce the range of any thermally induced stresses (e.g., the difference between the maximum tensile and compressive stress) experienced by the component as a result of these temperature differences.

[0067] As an example, in a nuclear fusion plasma confinement device, plasma is expected to pulse on and off cyclically. In experimental nuclear fusion tokamaks, plasma pulses can range in duration from milliseconds to tens or hundreds of seconds; in commercial reactors, plasma pulses are expected to run for several hours, or longer. During a pulse, components, in particular plasma-facing components (PFCs) of the plasma confinement device are heated up by the hot plasma, whereas between pulses, these components cool down. This cyclic heating and cooling can induce cyclic thermal stresses in components of the system, as each component expands and contracts and heats up and cools down at different rates. This cyclic thermal loading can accelerate fatigue. Maintaining the component at elevated temperature (e.g., a temperature closer to the

[0068] 37939900-1expected operating temperature) is one way to reduce the number of cooling cycles and / or the range of any induced thermal stresses experienced by the components.

[0069] The inventors have realised that a heat pipe may be designed to operate both to extract thermal energy from a component and to convey thermal energy to the component. That is, heat pipes are reversible, in the sense that the condenser and evaporator portion of the heat pipe are interchangeable, if the temperature difference across the heat pipe switches sign.

[0070] This reversibility in the mode in which heat pipes can operate advantageously means that separate “heating” and “cooling” systems for the component are not required: the same heat pipe (and heat exchanger) can form both the cooling and the heating system for the component. This helps to improve space efficiency of the thermal management apparatus.

[0071] Coupled to this, the inventors have realised that, for components that are subject to cyclic temperature requirements (e.g., which are heated then cooled cyclically), some of the thermal energy conveyed to the heat exchanger during cooling of the component can be used to provide heating to the component during the heating cycle. This improves the energy efficiency for cyclically cooling and heating the component.

[0072] Figure 4 is a schematic illustration of a plasma confinement device 400 (e.g., a spherical tokamak) shown in cross-section. The figure is symmetrical both left-right and topbottom, and for clarity reference numerals have not been duplicated for symmetrical components. It will be understood that the plasma confinement device may, in other examples, be asymmetrical left-right and / or top-bottom.

[0073] The plasma confinement device 400 further includes a lower 410 and an upper divertor 420, which are arranged within a plasma confinement chamber 430. Upper refers to an upward direction relative to gravity, whereas lower refers to a downward direction relative to gravity. In use, a plasma 440 is generated within the plasma confinement chamber and heat and ash are exhausted via one or both divertors. In some examples, the plasma confinement device may include one of a lower or an upper divertor.

[0074] 37939900-1Each of the lower and upper divertor includes a plurality of divertor surfaces (surfaces 410a, 410b, 410c of the lower divertor and 420a, 420b, 420c of the upper divertor). Lower divertor 410 has an inboard divertor surface 410a, an outboard divertor surface 410c, and an intermediary divertor surface 410b. Upper divertor 420 has an inboard divertor surface 420a, an outboard divertor surface 420c, and an intermediary divertor surface 420b. The intermediary divertor surfaces 410b, 420b are shown in Figure 4 as planar. In some examples the intermediary divertor surfaces 410b, 420b may be dome-shaped and referred to as dome surfaces. Outboard refers to a direction radially outward relative to a central axis 404 defined by a central column 402 of the plasma confinement device, whereas inboard refers to a direction radially inward relative to the central column.

[0075] The plasma confinement device 400 further comprises a magnetic confinement system (e.g., a plurality of poloidal field coils 406 and toroidal field coils (not shown)) to control the plasma 440.

[0076] Figure 5 is a schematic illustration of an upper divertor 420 in cross-section, substantially as shown in Figure 4 but with intermediary divertor surface 420b assuming a domed profile rather than a planar profile.

[0077] It is noted that Figure 5 shows an upper divertor of the plasma confinement device only. In some examples, the plasma confinement device may include both an upper and a lower divertor or only a lower divertor. If present, the lower divertor may include a corresponding set of divertor surfaces, for example, a lower inboard divertor surface, a lower outboard divertor surface, and a lower intermediary (e.g., dome) surface.

[0078] The upper divertor incorporates a thermal management apparatus 500 according to an embodiment, denoted by reference numeral 500. The thermal management apparatus 500 comprises a component 502, which includes or forms the divertor surface, a heat pipe 504 and a heat exchanger 506 operatively coupled to the heat pipe. The arrows F in the figure denote the expected direction of the incident thermal flux originating from the plasma 440 (in Figure 5 only the upper portion of plasma 440 is shown) during operation. As shown, the thermal flux impinges on the divertor surface 420a at an oblique angle.

[0079] 37939900-1The heat pipe includes a channel (not shown) for the working fluid. The channel may be elongate. The channel has a plurality of dimensions, which dimensions include a major dimension (e.g., a length) and a minor dimension (e.g., a thickness). The major dimension is greater than the minor dimension. The channel also includes a further dimension (e.g., a width). The further dimension is equal to or less than the major dimension but may be smaller, greater, or equal to the minor dimension. In Figure 5, the component and the heat exchanger oppose (i.e. , face opposite to) one another in a direction transverse to a direction which defines a major dimension of the channel (e.g., transverse to the elongate channel of the heat pipe).

[0080] The component is shown as a block element in Figure 5 for simplicity. In some examples, the component comprises a plurality of physically distinct units (e.g., divertor blocks, monoblocks, plates, or tiles). This is shown in more detail in Figures 9A, 9B, and 10, for example.

[0081] As shown, the thermal management apparatus 500 includes a coolant feed line 508 and coolant return line 510 through which a coolant can be pumped into and out from the heat exchanger. The arrows in the figure denote the direction of the coolant flow through the coolant lines during operation. The arrangement of the coolant lines in the figure is schematic and it will be understood that the coolant lines may be arranged in other configurations.

[0082] It is noted that for brevity, and to avoid confusion with the working fluid in the heat pipe, the term “coolant,” rather than a more general term such as “heat exchange fluid,” is used in the previous paragraph and throughout the remainder of description that follows. It will be understood that the “coolant” may be used either for heating or for cooling the component, depending on the mode of operation of the thermal management apparatus, that is, on whether the intent is to heat or to cool the component.

[0083] The thermal management apparatus further comprises one or more pumps 512 operatively coupled to the heat exchanger for pumping coolant through the coolant lines. The coolant may be pumped from a source of coolant (which is not shown in Figure 5 for simplicity). One or more actuators 514 (e.g., one-way valves) are arranged in between

[0084] 37939900-1the one or more pumps and the heat exchanger for regulating the flow rate of the coolant entering the heat exchanger. The one or more pumps and the one or more actuators are operated or controlled by one or more controllers 516 It will be understood that the one or more actuators 514 and pumps 512 may be controlled by a respective controller (as shown in the figure) or by a common controller.

[0085] In order to regulate the temperature of the component 502, the thermal management apparatus may comprise one or more sensors for determining a temperature of, or across, the component and / or the heat exchanger 506. The temperature may be determined directly or indirectly. For example, the temperature of the component may be measured directly using infrared sensors, or indirectly by measuring the temperature and / or pressure within heat pipe.

[0086] The or each temperature sensor is configured to transmit or otherwise convey its measurements to the one or more controllers 516. The one or more controllers may then process the measurements in order to determine whether the component is overheating (e.g., has reached or exceeds a predetermined or computed maximum allowable temperature). Conveyance of the measurements to the controller(s) is shown in the figure by the arrows connecting component 502 with controller(s) 516 and by the arrows connecting temperature sensor 518, described below, with controller(s) 516.

[0087] In response to a determination that the component is overheating, the one or more controllers may adjust one or more operating parameters for the heat exchanger, for instance, increasing a pumping rate (e.g., by pumping pump 512 harder and / or by actuating the actuator 514 further open) and / or decreasing a temperature of the coolant being pumped into the heat exchanger.

[0088] In the specific example shown in Figure 5, the thermal management apparatus 500 comprises a temperature sensor 518 arranged within or in the proximity of the return coolant line for measuring a temperature of the coolant exiting the heat exchanger, and one or more infrared sensors (not shown) for measuring a temperature across the component. It will be understood that there may be a plurality of temperature sensors arranged within and / or along each of the coolant lines, each sensor of the plurality being configured to transmit or otherwise convey its measurements to the one or more controllers.

[0089] 37939900-1The thermal management apparatus 500 further comprises a coolant storage unit 520 operatively coupled to the return coolant line 510. The coolant storage unit may be operatively coupled to the coolant feed line 508 via one or more actuators 522 (e.g., a one-way valve) and / or to a power generating system (not shown). The one or more actuators 522 may be operated using the one or more controllers 516.

[0090] The coolant storage unit 520, actuators 514, 522, temperature sensor 518, pump 512 and one or more controllers 516 may be located within or outside of the plasma confinement chamber 430.

[0091] While a plasma 440 is present within the plasma confinement device 400 (e.g., during a pulse), the component 502 will be heated up by the heat being exhausted into the divertor 420. In turn, thermal energy will be transferred from the component to the heat exchanger 506 via the heat pipe 504. During this time, coolant is heated up as it passes through the heat exchanger. That is, the temperature of the coolant at the feed coolant line 508 will be less than the temperature of the coolant at the return coolant line 510. The coolant may then pass into and be stored within coolant storage unit 520. In this way, while a plasma is present within the plasma confinement device, the coolant storage unit will accumulate thermal energy and function as a store for thermal energy.

[0092] While a plasma 440 is absent from the plasma confinement device 400 (e.g., in between plasma pulses), the absence of thermal flux or energy being exhausted from the plasma may permit the component to cool down (e.g., be that passively by radiation or actively using the heat exchanger). Overcooling the component may, however, increase the thermal stresses associated with switching the plasma back on, and so is undesirable.

[0093] The inventors have realised that, between plasma pulses or before the first plasma pulse, it is desirable to maintain the component 502 within an allowable temperature range (e.g., above a minimum allowable temperature) in order to reduce the associated thermal stresses that are induced within the component after the plasma is switched on.

[0094] In some examples, thermal energy stored in the coolant storage unit 520 may be used to provide heating of the component in an energy-efficient manner (i.e. , without the need to heat up coolant afresh).

[0095] 37939900-1Figure 6 is a schematic illustration of the upper divertor 420 in cross section, substantially as shown in Figure 4, but showing only the inboard divertor surface 420a.

[0096] It is noted that Figure 6 shows an upper divertor of the plasma confinement device only. In some examples, the plasma confinement device may include both an upper and a lower divertor or only a lower divertor. If present, the lower divertor may include a corresponding set of divertor surfaces, for example, a lower inboard divertor surface, a lower outboard divertor surface, and a lower intermediary (e.g., dome) surface.

[0097] The upper divertor incorporates a thermal management apparatus 600 according to an embodiment, denoted by reference numeral 600. The thermal management apparatus 600 shown in Figure 6 is a variant of the thermal management apparatus 500 shown in Figure 5. The thermal management apparatus 600 comprises a component 602, which includes or forms the divertor surface, a heat pipe 604 and first and second heat exchangers 606a, 606b operatively coupled to the heat pipe. In some examples, there may be only one heat exchanger. In other examples, there may be more than two heat exchangers (e.g., where there are multiple heat pipes). The arrows F in the figure denote the expected direction of the incident thermal flux originating from the plasma 440 (in Figure 6 only the upper portion of plasma 440 is shown) during operation. As shown, the thermal flux impinges on the divertor surface 420a at an oblique angle.

[0098] The heat pipe includes a channel (not shown) for the working fluid. The channel may be elongate. The channel has a plurality of dimensions, which dimensions include a major dimension (e.g., a length) and a minor dimension (e.g., a thickness). The major dimension is greater than the minor dimension. The channel also includes a further dimension (e.g., a width). The further dimension is equal to or less than the major dimension but may be smaller, greater, or equal to the minor dimension.

[0099] In some examples, the first and second heat exchangers 606a, 606b are operatively coupled to the heat pipe at respective longitudinal ends of the heat pipe (if the elongate channel of the heat pipe has ends). In other examples, the heat pipe includes one or more bends of the elongate channel (e.g., if the elongate channel forms a closed loop without ends). In a specific example, the one or more bends are serpentine bends and the elongate channel traces a serpentine path.

[0100] 37939900-1The component is shown as a block element in Figure 6 for simplicity. In some examples, the component comprises a plurality of physically distinct units (e.g., divertor blocks, monoblocks, plates, or tiles). This is shown in more detail in Figures 13 and 14A-14C, for example.

[0101] The thermal management apparatus 600 includes a coolant feed line 608 and coolant return line 610 for each heat exchanger. This is shown in Figure 6 as coolant feed line 608 and coolant return line 610 for heat exchanger 608a; for simplicity, the corresponding feed and return lines for heat exchanger 608b are not shown. In use, a coolant is pumped into and out from each or the heat exchanger 606a, 606b via the coolant feed and return lines. The arrows in the figure denote the direction of the coolant flow through the coolant lines during operation. The arrangement of the coolant lines in the figure is schematic and it will be understood that the coolant lines may be arranged in other configurations.

[0102] The thermal management apparatus 600 further comprises one or more pumps 612 operatively coupled to the heat exchanger(s) for pumping coolant through the coolant lines. The coolant may be pumped from a source of coolant (which is not shown in Figure 6 for simplicity). One or more actuators 614 (e.g., one-way valves) are arranged in between the one or more pumps and the heat exchanger(s) for regulating the flow rate of the coolant entering the heat exchanger(s). The one or more pumps and the one or more actuators are operated or controlled by one or more controllers (denoted collectively as 616 in the figure). The temperature may be determined directly or indirectly. For example, the temperature of the component may be measured directly using infrared sensors, or indirectly by measuring the temperature and / or pressure within heat pipe.

[0103] In some examples, the heat pipe may be operated to cool the component when plasma is present in the plasma confinement device and operated to heat the component when plasma is absent from the plasma confinement device. However, it will be understood that, even after the plasma is extinguished, divertor temperatures remain elevated (and potentially above the maximum allowable temperature) for a period of time. The heat pipes may be operated to continue cooling the component, even after the plasma is extinguished (i.e., is absent from the plasma confinement device). Temperature

[0104] 37939900-1measurements from the one or more temperature sensors can be used to determine at which point the temperature of, or associated with, the component becomes less than the maximum allowable temperature in order to determine when to switch the heat pipe from a cooling to a heating operational mode. Temperature measurements from the one or more temperature sensors can also be used to determine if the component is at a temperature less than or equal to the minimum allowable temperature, to keep the component from overcooling.

[0105] The or each temperature sensor is configured to transmit or otherwise convey its measurements to the one or more controllers 616. The one or more controllers may then process the measurements in order to determine whether the component is overheating (e.g., has reached or exceeds a predetermined or computed maximum allowable temperature).

[0106] In response to a determination that the component is overheating, the one or more controllers may adjust one or more operating parameters for the heat exchanger, for instance, increasing a pumping rate (e.g., by pumping pump 612 harder and / or by actuating the actuator 614 further open) and / or decreasing a temperature of the coolant being pumped into the heat exchanger.

[0107] In the specific example shown in Figure 6, the thermal management apparatus 600 comprises a temperature sensor 618 arranged within or in the proximity of the return coolant line for measuring a temperature of the coolant exiting the heat exchanger, and one or more infrared sensors (not shown) for measuring a temperature across the component. It will be understood that there may be a plurality of temperature sensors arranged within and / or along each of the coolant lines, each sensor of the plurality being configured to transmit or otherwise convey its measurements to the one or more controllers.

[0108] The thermal management apparatus 600 further comprises a coolant storage unit 620 operatively coupled to the return coolant line 620. The coolant storage unit may be operatively coupled to the coolant feed line 608 via one or more actuators 622 (e.g., a one-way valve) and / or to a power generating system (not shown). The one or more actuators 622 may be operated using one or more controllers 616.

[0109] 37939900-1For simplicity, the second heat exchanger 606b is not shown as being associated with the features of a pump 612, an actuator 614, a feed coolant line 608, a return coolant line 610, one or more controllers 616, one or more temperatures sensors 618, or a coolant storage unit 620. It will be understood that the second heat exchanger 606b may include these features and that these features may be shared with or separate from those features associated with the first heat exchanger 606a. For example, the second heat exchanger may be associated with its own coolant storage unit (not shown), or it may share the same coolant storage unit 620 as the first heat exchanger.

[0110] As with the corresponding elements in Figure 5, the coolant storage unit 620, actuators 614, 622, temperature sensor 618, pump 612 and one or more controllers 616 may be located within or outside of the plasma confinement chamber 430.

[0111] While a plasma 440 is present within the plasma confinement device 400 (e.g., during a pulse), the component 602 will be heated up by the heat exhausted into the divertor 420. In turn, thermal energy will be transferred from the component to the or each heat exchanger 606a, 606b via the heat pipe 604. During this time, coolant is heated up as it passes through the heat exchanger. That is, the temperature of the coolant at the or each feed coolant line 608 will be less than the temperature of the coolant at the corresponding return coolant line 610. The coolant may then pass into and be stored within coolant storage unit 620. In this way, while a plasma is present within the plasma confinement device, the coolant storage unit will accumulate thermal energy and function as a store for thermal energy.

[0112] While a plasma 440 is absent from the plasma confinement device 400 (e.g., in between plasma pulses), the absence of thermal energy being exhausted from the plasma may permit the component to cool down (e.g., be that passively by radiation or actively using the heat exchanger). Overcooling the component, however, may increase the thermal stresses associated with switching the plasma back on. The inventors have realised that, between plasma pulses or before the first plasma pulse, it is desirable to maintain the component 602 within an allowable temperature range (e.g., above a minimum allowable temperature) in order to reduce the associated thermal stresses that are induced in the component after the plasma is switched on.

[0113] 37939900-1In some examples, thermal energy stored in the coolant storage unit 620 may be used to provide heating of the component in an energy efficient manner (i.e., without the need to heat up coolant afresh).

[0114] Each of Figures 7A, 7B and 7C is a schematic illustration of a cross section of the thermal management apparatus 500 from Figure 5, showing the component 502, the heat pipe 504 and the heat exchanger 506. For simplicity, other elements of the apparatus 500 are not shown in these figures. The heat pipe 504 is affixed to and in thermal contact with the component 502 at an attachment portion (not shown) of the component. Two objects or systems are in thermal contact if thermal energy can be transferred between them (e.g., if there exists a temperature difference between them and there is no barrier to thermal energy transfer between them).

[0115] It will be appreciated that the heat pipe 504 may be affixed either directly or indirectly to the component 502 so long as the component and heat pipe remain in thermal contact. That is, the heat pipe and the component may be in direct physical contact with one another, or they may be spatially separated from one another by one or more interlayers. Example interlayers include bonding materials between the heat pipe and component, such as solders, brazes, and adhesives. Alternatively, or in addition, the heat pipe and component may be bonded together via a further spacing interlayer which is then affixed to each of the component and heat pipe.

[0116] In Figure 7A, the component 502 is at a higher temperature than the heat exchanger 506. This represents a “cooling” cycle for the component because the heat pipe 504 is operated in a first mode to extract thermal energy from the component 502 and to convey that thermal energy to the heat exchanger 506. This helps to prevent the component 502 from overheating (e.g., keeping it below a predetermined or computed maximum allowable temperature). Thermal energy therefore flows from the component into the heat pipe (denoted Qi) in the figure.

[0117] A portion of this thermal energy is received by the heat pipe 504. The operating parameters of the heat exchanger 506 can be adjusted or controlled as desired to increase or decrease the thermal energy received by the heat pipe 504.

[0118] 37939900-1The heat pipe 504 conveys at least a portion (denoted Ch) of the received thermal energy to the heat exchanger 506. The heat pipe 504 also conveys at least a portion of the received thermal energy along its channel (which may be elongate).

[0119] In Figure 7B, the component 502 is at a lower temperature than the heat exchanger 506. This represents a “heating” cycle for the component because the heat pipe is operated in a second mode to convey thermal energy to the component from the heat exchanger. This helps to prevent the component from overcooling (e.g., keeping it above a predetermined or computed minimum allowable temperature). Thermal energy therefore flows from the heat exchanger into the heat pipe (denoted Ch) in the figure.

[0120] A portion of this thermal energy is received by the heat pipe 504. The operating parameters of the heat exchanger 506 can be adjusted or controlled as desired to increase or decrease the thermal energy received by the heat pipe. In some examples, decreasing the flow of thermal energy from the heat exchanger 506 to the component 502 can allow the component 502 to cool down passively (e.g., by radiative cooling).

[0121] The heat pipe 504 conveys at least a portion (denoted CU) of the received thermal energy to the component 502. The heat pipe 504 also conveys at least a portion of the received thermal energy along its channel (which may be elongate).

[0122] In Figure 7C, the component 502 is at a lower temperature than the heat exchanger 506 but, unlike in Figure 7B, the temperature of the component is higher than desired. This represents a “heating” cycle for the component because the heat pipe remains in the second mode, in which it conveys thermal energy to the component.

[0123] As with Figure 7B, the heat pipe 504 receives a portion of thermal energy (Qs) from the heat exchanger 506. Unlike Figure 7B, however, the operating parameters of the heat exchanger are controlled or adjusted to decrease the thermal energy received by the heat pipe. For instance, the operating parameters may be controlled in order to reduce the rate of coolant flow through the heat exchanger, or to turn off the flow altogether. The relative lengths of the arrows in Figure 7B and 7C denote that less thermal energy is transferred between the heat pipe and heat exchanger in Figure 7C than in Figure 7B.

[0124] 37939900-1The heat pipe 504 conveys at least a portion (denoted Qe) of the received thermal energy to the component 502. Comparing to Figure 7B, less thermal energy is transferred to the heat pipe in Figure 7C, and so less thermal energy is transferred to the component. In some examples, this can allow the component to cool down passively (e.g., by radiative cooling, where the radiative cooling rate exceeds the rate at which heat comes into the component from the heat pipe).

[0125] It will be understood that, while Figures 7A to 7C show a portion of the thermal management apparatus from Figure 5, the same principles apply to the thermal management apparatus from Figure 6.

[0126] Figure 8 is a method flow diagram of a thermal management method 800, according to an embodiment. The method may be carried out by any one of the thermal management apparatus (e.g., the thermal management apparatus from Figure 5 or 6) described herein.

[0127] In step 805, a controller such as controller(s) 516, 616, receives information to use as control inputs. This information may include any information relevant to a decision of whether to heat or cool the component using the heat pipes 504, 604, such as information about: measured temperature(s) or temperature profile at the component, and / or at or in the coolant lines; whether there is, or is not, a plasma in the plasma confinement device; the timing of the plasma pulse cycles and, if there is no plasma in the device at present, when the last plasma pulse was and / or when the next pulse is scheduled or anticipated to begin; whether the plasma is in a stable configuration, or whether there is or is likely to be a plasma disruption; etc.

[0128] In step 810, a decision is made whether to operate the heat pipe so as to heat the component. If the decision is to do so, the method proceeds to step 815; if not, then to step 820.

[0129] In step 815, the heat pipe 504, 604 is operated in a first mode to extract thermal energy from the component 502, 602. This may be achieved by adjusting or modifying operating parameters of the heat exchanger(s) 506, 606a, 606b to ensure that the temperature at the or each heat exchanger is lower than the temperature(s) at the component and, in some examples, to ensure that the temperature differential between the component and

[0130] 37939900-1the heat exchanger(s) exceeds a predetermined or computed value. For example, fresh coolant at low or ambient temperature may be pumped through the heat exchanger(s); and the pressure and / or flow rate of the coolant may be adjusted. After step 815, the method returns to step 805. In some examples, the operating parameters of the heat exchanger may be adjusted or modified to cause the heat pipe to operate in the first mode and / or increase the thermal energy extracted from the component.

[0131] In step 820, a decision is made whether to operate the heat pipe so as to cool the component. If the decision is to do so, the method proceeds to step 825; if not, then back to step 805.

[0132] In step 825, the heat pipe 504, 604 is operated in a second mode to convey thermal energy to the component 502, 602. This may be achieved by adjusting or modifying the heat exchanger operating parameters to ensure that the temperature at the or each heat exchanger is higher than the temperature(s) at the component and, in some examples, to ensure that the temperature differential between the component and the heat exchanger(s) exceeds a predetermined or computed value. For example, previously heated coolant from coolant storage unit 520, 620 and / or from an external source may be pumped through the heat exchanger(s); and the pressure and / or flow rate of the heated coolant may be adjusted.

[0133] The thermal power extracted or provided by the heat pipe when operated in the first mode and second mode, respectively, is at least a function of the rate of heat transfer between the heat pipe and the heat exchanger to which the heat pipe is operatively coupled. Control of this heat transfer rate is one way to control the thermal power provided to or extracted from the component during operation. The heat transfer rate can be controlled by one or more operating parameters of the heat exchanger, namely any one or more of: a coolant temperature through the heat exchanger; a coolant flow rate through the heat exchanger; a coolant pressure through the heat exchanger; and a coolant composition through the heat exchanger.

[0134] In some examples, the heat pipe is operated in the first mode (step 815) while a plasma is present in the plasma confinement device. For example, in a device such as plasma confinement device 400 with plasma confinement chamber 430 as was shown in Figure 4, the heat pipe may be operated in the first mode when there is plasma 440 present in

[0135] 37939900-1the plasma confinement chamber 430. It is also possible to operate the heat pipe in the first mode at times when there is no plasma in the plasma confinement chamber. For example, if the plasma confinement device is operated in a pulsed mode, the component 502, 602 will remain quite hot for some time following the end of a plasma pulse, in which case it may be advantageous to continue to cool component 502, 602 actively by continuing to operate the heat pipe 504, 604 in first mode until such time as the component has reached a minimum allowable temperature.

[0136] In some examples, the heat pipe is operated in the second mode (step 825) while plasma is absent from the plasma confinement device. For example, in a device such as plasma confinement device 400 with plasma confinement chamber 430 as was shown in Figure 4, the heat pipe may be operated in the second mode when plasma 440 is absent from the plasma confinement chamber 430 (or in other words, when there is no plasma 440 present in the plasma confinement chamber 430). If the plasma confinement device is operated in a pulsed mode, the component 502, 602 may be kept at a minimum allowable temperature between plasma pulses by operating heat pipe in the second mode to supply heat to the component until such time as the next pulse begins or is soon to begin.

[0137] It will be understood that providing thermal energy to a component may or may not cause the component to increase in temperature (be that a local temperature across a portion of the component, or an average temperature across the entire component). In general, it will reduce the cooling rate of the component. This means that, when the heat pipe is operated in the second mode, the cooling rate of the component can be positive, zero, or negative.

[0138] It will be understood that the numbering of the method steps in Figure 800 is not intended to impose a strict ordering. Steps 810 and 815 may, for example, be carried out before steps 820 and 825.

[0139] In some examples, the heat pipe 504, 604 alternates (and in some instances regularly) between operating in the first and the second mode, according to (though not necessarily in strict synchrony with) the cycle of on-off plasma pulses. For example, changing from operating the heat pipe in the first mode to operating the heat pipe in the second mode may be contemporaneous with or in response to an end of a plasma pulse in the plasma confinement device; and changing from operating the heat pipe in the second mode to

[0140] 37939900-1operating the heat pipe in the first mode may be contemporaneous with or in anticipation of a start of a plasma pulse in the plasma confinement device. In this way, the cycle of operating the heat pipe in first and second mode may be chosen so as to reduce or minimise the thermal stress effects of cyclical heating and cooling on the component. In other examples, there may not be a strict alternation between operating in the first and second modes.

[0141] In some examples, the heat pipe may operate in the first mode while a temperature of, or associated with, the component is greater than or equal to a maximum allowable temperature, so as to keep the component from overheating, and may operate in the second mode while the temperature of, or associated with, the component is less than or equal to a minimum allowable temperature, to keep the component from overcooling.

[0142] In some examples, the heat pipe switch from operating in the first mode to operating in the second mode in response to a determination that a plasma in the plasma confinement device has been lost or otherwise disrupted. For example, the switch to the second mode may take place immediately after such a determination, or after some delay to allow for cool-down of the component.

[0143] In a specific example, the change of the heat pipe from operating in the second mode to operating in the first mode coincides with a start of a plasma pulse in the plasma confinement device. In another example, the change may be made in advance of the start of a plasma pulse; or the heat exchanger may temporarily have its (heated) coolant flow switched off shortly before the start of the plasma pulse, and then have its (low or ambient temperature) coolant flow switched on nearer to, or coincident with, the start of the pulse.

[0144] By providing or extracting thermal energy to and from the component 502, 602, the temperature of the component can be managed, e.g., kept within a range between maximum and minimum allowable temperatures. There may be respective maximum and minimum allowable temperatures for the component, a range corresponding to when the component is being heated up (e.g., while the plasma is present) and another range corresponding to when the component is being cooled down (e.g., while plasma is absent). As has already been noted, the proposed method 800, in which the same heat

[0145] 37939900-1pipe is used to provide both heating and cooling of the component, is space efficient as separate heating and cooling systems for the component are not necessarily required.

[0146] It will be appreciated that in some examples, the heat pipe 504, 604 conveys thermal energy from the component 502, 602 to the heat exchanger 506, 606a, 606b in the first mode and conveys thermal energy from that same heat exchanger back to the component in the second mode. As has already been noted, the use of the same heat exchanger in the thermal management apparatus is energy efficient as thermal energy provided to the heat exchanger during the cooling cycle can be, at least partially, used to provide heat for the heating cycle of the component.

[0147] In some examples, the heat pipe is operated in the first or second mode depending on a spatial temperature distribution across the component or a coolant temperature in the return coolant line. For example, the heat pipe may be operated in the first mode if it is determined that the temperature of, or a temperature associated with, the component (or the coolant temperature in the return coolant line) exceeds a maximum allowable temperature. It will be understood that the maximum allowable temperature for the coolant and for the component will be different. The operation of the heat pipe in the first mode helps to reduce the temperature of the component (e.g., avoid or mitigate overheating). Similarly, the heat pipe may be operated in the second mode if it is determined that the minimum temperature of, or associated with, the component (or the coolant temperature in the return coolant line) is less than a minimum allowable temperature. Again, it will be understood that the minimum allowable temperature for the coolant and for the component will be different. The operation of the heat pipe in the second mode helps to maintain the temperature of the component (e.g., avoid or mitigate overcooling).

[0148] A temperature associated with a component can be, for example, one temperature among a set of temperatures in a temperature profile measurement across the component, such as a maximum, near-maximum, second-from-maximum, or other temperature chosen from the profile; a mean or median temperature; or any other temperature that may be taken as representative of whether the component is within its allowable temperature range.

[0149] 37939900-1The spatial temperature distribution of the heat pipe or component may be acquired directly through measurement using one or more temperature sensors (e.g., infrared sensors). In this regard, the apparatus may comprise one or more temperature sensors (e.g., an array of temperature sensors), each of which is configured to acquire a temperature at a corresponding position or region of the component. In a specific example, the position or region of the component may be associated (e.g., is contained within or overlaps with) with a particular attachment portion (e.g., 922a-i, 1322a-i, as shown in Figure 9A or 13) of the heat pipe or a portion thereof.

[0150] In some examples, as described above in relation to Figure 7C, the component may be too hot, despite being at a lower temperature than the heat exchanger. That is, a maximum temperature of the component may be greater than a maximum allowable temperature but where the heat pipe is operating in the second mode.

[0151] In such examples, it may be possible to adjust or modify the operating parameters of the heat exchanger to allow the component to cool passively, instead of switching the heat pipe to operate in the first mode (which requires the heat exchanger to be at a lower temperature than the component). For example, the operating parameters of the heat exchanger can be adjusted to reduce a magnitude of heat transfer rate between the heat pipe and the heat exchanger, such that less thermal energy is conveyed to the component from the heat exchanger. If the component is losing heat to its surroundings (e.g., by radiative cooling), then, at least temporarily, the decrease in thermal energy provided by the heat exchanger can lead to the component losing a net positive energy (i.e. , causing a decrease in temperature).

[0152] Primarily, this is a function of the temperature differential between the coolant in the heat exchanger and the component: if the temperature differential is positive (i.e., the coolant is hotter than the component), then the heat pipe operates in the second mode; and if the temperature differential is negative (i.e., the coolant is cooler than the component), then the heat pipe operates in the first mode.

[0153] By way of example, the coolant of the heat exchanger can be any one or more of: water, a molten metal, a molten salt, an inert gas, or carbon dioxide.

[0154] 37939900-1In some examples, the thermal management apparatus comprises a plurality of heat pipes in thermal contact with the component. The heat pipes may be arranged in an array (herein “heat pipe array”) that extends across or spans the component. Each heat pipe in the heat pipe array may be affixed to the component at a corresponding attachment portion of the component. The plurality of heat pipes can be operatively coupled to the same or shared heat exchanger or to different heat exchangers (e.g., one of a plurality of different heat exchangers). In a specific example, one or more neighbouring or adjacent heat pipes in the heat pipe array share a common heat exchanger.

[0155] In some examples, each heat pipe in the heat pipe array operates in unison (or in synchrony). That is, at any given time, all of the heat pipes in the heat pipe array may operate together in the first mode or the second mode.

[0156] Figure 9A is a cross-sectional view of the thermal management apparatus 500 from Figure 5. As shown, the thermal management apparatus 500 comprises a component 502, a heat pipe 504 and a heat exchanger 506 operatively coupled to the heat pipe. The heat pipe includes a channel 920, which may be elongate. The channel has a plurality of dimensions, which dimensions include a major dimension (e.g., a length) and a minor dimension (e.g., a thickness). The major dimension is greater than the minor dimension. Although not visible in cross-section, the channel also includes a further dimension (e.g., a width). The further dimension is equal to or less than the major dimension but may be smaller, greater, or equal to the minor dimension. The heat exchanger and component are spaced apart in a direction defining the minor dimension (e.g., a thickness direction).

[0157] As shown, the heat pipe spaces apart the heat exchanger 506 and the component 502 in a direction transverse to a direction defining a major dimension of the channel. In a specific example, the channel is elongate and the heat exchanger 506 and the component 502 are spaced apart by the heat pipe in a direction transverse to the elongate channel. In Figure 9A, the heat pipe is shown as including a wick 908 but this is for illustrative purposes only. It will be understood that the heat pipe 404 may have a wick or may be wickless, and may be of any known type.

[0158] In use, a thermal flux profile 910 is incident onto and strikes the component 502. The heat pipe 504 is therefore being operated in the first mode. An example thermal flux

[0159] 37939900-1profile 910 is shown in Figure 9A. The spatial distribution of the thermal flux (i.e., the thermal flux profile) that strikes the component is non-uniform (i.e., the magnitude of the thermal flux that strikes the incidence surface of the component varies with position across that surface) and the profile exhibits a peak or maximum. In some examples, the thermal flux profile is asymmetric and may be skewed in a direction towards heat exchanger 506. The thermal energy caused to flow from the component 502 to the heat exchanger 506 is denoted by the arrows within the channel in the figure. It will be understood that these arrows represent a simplified view of the flow of thermal energy.

[0160] The thermal flux profile 910 causes the component 502 to heat up in accordance with the thermal flux profile. That is, the thermal flux profile causes the component to heat up more at positions closer to the location of the peak of the thermal flux profile, as compared to positions that are further away from the peak. This generates a temperature hot spot 912 within the component (the boundary of which is denoted by the vertical dotted lines in the figure). The size of the hot spot 912 may be the full-width at halfmaximum, FWHM, of the temperature profile at the component. For asymmetric hot spots, an average FWHM can be used.

[0161] The heat pipe 504 is in thermal contact with the component 502. Heat pipe 504 therefore receives thermal energy from the component 502. The thermal flux profile received by the heat pipe (not shown in Figure 9A) is, to a first approximation, similar in shape and size to profile 910. That is, the heat pipe receives a thermal flux that varies with position (e.g., along its length) and which exhibits a peak.

[0162] In turn, the heat pipe 504 and the working fluid within the heat pipe is heated in accordance with the thermal flux that it locally receives. This causes a region of greatest evaporation of the working fluid (denoted in Figure 9A by the darkened region 914 in wick 908) to form within the heat pipe and / or at the envelope 916 of the heat pipe. The region of greatest evaporation 414 within the heat pipe and the hot spot 912 within the component may be substantially co-located.

[0163] Heat pipes are sometimes referred to colloquially as “heat superconductors.” Heat is carried away rapidly from the evaporator region(s) of the heat pipe to the condenser region(s).

[0164] 37939900-1In the example of Figure 9A, the evaporation rate of working fluid within the heat pipe 504 varies spatially across the mutual interface between the heat pipe 504 and the component 502 in accordance with the spatial distribution of the thermal flux that the heat pipe receives at that interface. The “heat superconductor” property of heat pipes makes heat pipe 504 effective at spreading out the heat from hot spot 912 of the component (the exact location of which may not be known) so that the thermal flux across the mutual interface between the heat pipe and the heat exchanger can be made relatively uniform, and less than the maximum thermal flux received by the heat pipe in the vicinity of the hot spot(s) of the component. In this way, the heat exchanger 506 need not be designed to accommodate the maximum thermal flux received at the component 502, as would otherwise be the case absent the heat-spreading capability of the heat pipe 504.

[0165] The heated working gas (i.e. , the vaporised working liquid) moves through the heat pipe 504 away from the hot spot 912 along a direction defining a major dimension of the channel of the heat pipe 504, and also moves through the heat pipe 504 towards the heat exchanger 506 in a direction transverse to the direction defining the major dimension of the channel (or, in other words, in a direction defining the minor dimension of the channel).

[0166] In a specific example, the channel is elongate and the working gas moves away from the hot spot along the length of the channel and towards the heat exchanger in a direction across the thickness direction of the channel. As another example, if the heat pipe is of a planar design rather than a tubular design (e.g., where the heat pipe is a vapour chamber), the working gas spreads out across the planar area of the channel and moves toward the heat exchanger in a direction across the thickness direction of the channel.

[0167] At the heat exchanger 506, the working gas condenses and releases its latent heat of condensation, which latent heat is extracted by the heat exchanger.

[0168] In this way, thermal energy is transferred from the hot spot 912 within the component 502 to the heat exchanger 506. Notably, as thermal energy is conveyed along a direction defining the major dimension of the channel (e.g., along the elongate channel) as it is conveyed to the heat exchanger, the thermal energy originating from the hot spot 912 is spread over a greater area at the heat exchanger 506. The greater area is denoted by

[0169] 37939900-1the grey region 928 within the wick 908 of the heat pipe in the vicinity of heat exchanger 506.

[0170] In some examples (not shown), there may be a plurality of hot spots at the component 502 and / or heat pipe 504, while the heat pipe is operated in the first mode. This may arise, for example, if the position of the peak in the thermal flux profile 910 varies with time faster than the thermal management apparatus can remove the presence of the previous hot spot. The heat spreading concept described above may apply to any one or each of these one or more hot spots.

[0171] Returning to Figure 9A in more detail, the component 502 comprises a plurality of physically distinct units (i.e., which are spatially separated from each other) illustratively shown as 902a-902i. For simplicity, only component 902a and 902i are labelled in the figure.

[0172] The physically distinct units 902a-i are arranged in a castellated structure. It will be understood that the component may comprise any number of these units (e.g., more or fewer units than shown in the figure). In some examples, the component comprises a multiplicity of units (e.g., more than 10, more than 20, more than 30, or more than 50).

[0173] The units 902a-i are described as being castellated as they form an outer surface that includes a series of spaced ridges or ridgeways 918 (which to some extent may resemble the battlements of a medieval castle). For clarity, only four of the eight ridgeways are labelled in the figure. The units may take various forms, for example, each unit may be a block, a tile, a plate, ora monoblock. Each unit has a thickness (in a thickness direction towards the heat pipe), a width and a length (in a plane orthogonal to the thickness direction).

[0174] Each of the plurality of units 902a-902i is in thermal contact with the heat pipe 504 and affixed to the heat pipe at or along a first portion 924 of the heat pipe. It will be appreciated that the heat pipe may be affixed either directly or indirectly to the plurality of units so long as the units and heat pipe remain in thermal contact. That is, the heat pipe and each unit may be in direct physical contact with one another, or they may be spatially separated from one another by one or more interlayers. Example interlayers include bonding materials between the heat pipe and component, such as solders,

[0175] 37939900-1brazes, and adhesives. Alternatively, or in addition, the heat pipe and component may be bonded together via a further spacing interlayer which is then affixed to each of the component and heat pipe.

[0176] In the example shown, the first portion 924 of the heat pipe 504 includes a plurality of physically distinct attachment portions 922a-i of the heat pipe 504. Each attachment portion 922a-i attaches a corresponding unit 902a-i of component 502 to heat pipe 504. For simplicity, only portions 922b and 922h are labelled in the figure. The first portion also includes portions of the heat pipe 504 situated in between adjacent units (e.g., between unit 902a and 902b), which portions being are co-located with the spaced ridgeways 918. The first portion presents the surface area of contact or interface between the heat pipe 504 and the component 502 and through which thermal flux can pass between the component and the heat pipe.

[0177] The heat pipe 504 further includes a second portion 926, which is operatively coupled to the heat exchanger 506. The second portion opposes (i.e., faces opposite to) the first portion in a direction transverse to a direction defining the major dimension of the channel of the heat pipe. That is, the first portion is on the other side of the heat pipe in the transverse direction of the channel (rather than in the longitudinal direction of the channel). In a specific example, the channel is elongate and the first portion opposes the second portion in a direction transverse to the elongate channel. The first and second portion of the heat pipe may both extend along (i.e., in the direction defined by) a direction defining the major dimension of the channel.

[0178] The second portion presents the surface area of contact between the heat pipe 504 and the heat exchanger 506 and through which thermal flux can pass between the heat pipe and the heat exchanger.

[0179] In use, the evaporator portion of the heat pipe 504 may include at least part of or all of the first portion 924.

[0180] In use, the condenser portion of the heat pipe may include at least part of or all of the second portion 926.

[0181] 37939900-1A perspective view of the thermal management apparatus from Figure 9A but showing three units 402a-c, rather than nine units, is shown in Figure 9B. The channel 920 is shown as being rectangular in cross-section but it will be understood that other shapes in cross-section are possible. A coolant line 530 that extends through the heat exchanger 506 is also shown.

[0182] It will be understood, when comparing Figure 5 with 9A or 9B, that thermal flux, F (as depicted in Figure 5) may generally impinge onto the component 502 at an oblique angle. Accordingly, the thermal flux may not only strike the units 902a-i on their incidence or plasma-facing surfaces but also on their lower peripheral surfaces (or upper peripheral surface for the lower divertor 410 if present) that extend between the plasma-facing surfaces and the surfaces facing away from the plasma.

[0183] The units 902a-i may be positioned and shaped so as to prevent heat flux F from directly striking heat pipe 504. In some examples, the spacing of the units 902a-i is designed to be small enough to prevent the thermal flux F from striking the heat pipe 504 directly. Alternatively, or in addition, the plasma-facing surface of each unit may be angled or bevelled (in the toroidal or poloidal direction) to shadow the spaces between the units (e.g., the underlying heat pipe 504). That is, the units 902a-i may be shaped to be non-rectangular (e.g., trapezoidal or rhomboidal) in cross-section, with the plasma-facing surfaces angled so as to shade or shadow the spaces between the units 902a-i from thermal flux F. In yet further examples, the cross-section of the units 902a-i may be non-uniform to achieve a similar effect (e.g., conical in the toroidal or poloidal direction).

[0184] In some examples, the heat pipe 504 is affixed to the component by an interlayer (not shown). The interlayer may be a solder, braze, ora separate material layer to be soldered or brazed between the body of the component and the heat pipe. Optionally, the coefficient of thermal expansion, CTE (e.g., at standard conditions and / or at operating temperature), for the interlayer is intermediate between the CTE of the envelope of the heat pipe and the CTE of the component. This reduces the induced thermal stresses in the apparatus during thermal loading.

[0185] In some examples, the heat pipe and the component are formed from the same material (e.g., a tungsten alloy). This advantageously avoids the need to design and / or select an

[0186] 37939900-1interlayer with an intermediate CTE (which for some material combinations can be challenging).

[0187] The heat pipe 504 may be any known type of heat pipe. The heat pipe channel 920 may be elongate or planar; if elongate, it may be straight and include one or more bends, which may be made up of one or more straight and / or curved sections. The external shape of the heat pipe may be made suitable to the particular application or installation; e.g., it may be smooth or include undulations. The heat pipe and / or its channel (if elongate) may follow or trace a contour of a smooth external shape of the component (e.g., the plasma-facing surface of the component). The contour may comprise one or more straight line segments, curves, or a combination of straight- and curved-line segments. The external shape of the heat pipe may be tubular or planar, with any cross-sectional shape (e.g., square, rectangle, hexagon, circle, etc.).

[0188] In an alternative embodiment, as shown in Figure 10, the heat pipe 504 is partially embedded within the component 502. For simplicity, the component in Figure 10 includes five units 1002a-1002e rather than nine units, as depicted in Figure 9A. It will be understood that the component may include any number (e.g., a multiplicity) of units.

[0189] In Figure 10, the attachment portions between the heat pipe and units 1002a-e are at least partially embedded within the units. If present, the interlayer is also embedded within the units 1002a-e.

[0190] In Figures 9A, 9B, and 10, the heat pipe 504 spans across the entirety of the component (i.e. , units 902a-i). In some examples, the heat pipe 504 may span across a majority (i.e. , more than 50%, 60%, 70%, 80%, 90%, or 95%) of the component.

[0191] The channels 920 in Figures 9A, 9B, and 10 are shown as being straight but in practice, the channels and / or the heat pipe 504 may include one or more bends. The bends may be contained within a plane that is equidistant from the heat exchanger and component or contained within a plane at an oblique angle thereto.

[0192] If the channel includes one or more bends, the major dimension of the channel is a total length of the channel, following those one or more bends. The direction defining the major dimension of the channel will, therefore, define a plurality of directions, which vary

[0193] 37939900-1along the length of the channel. “Along” the channel and “longitudinal” should be interpreted accordingly. Where the bends of the heat pipe lie substantially in a plane, then the direction transverse to the direction defining the major dimension of the channel, namely, through the thickness of the channel, remains the same regardless of the bends. For example, in an x-y-z Cartesian coordinate system, if the bends of the heat pipe are in a plane defined as the x-y plane, then transverse direction through the thickness of the heat pipe is along the z axis.

[0194] Figure 11 is a schematic illustration of a variant of the thermal management apparatus 500 from Figure 5 and 9A. The thermal management apparatus 1100 comprises a component 1102 having a plurality of units 1102a-e, a heat pipe 1104, and a heat exchanger 1106. The thermal management apparatus may be substantially as described in relation with Figures 9A, 9B, and 10, but, in this variant, the apparatus comprises a plurality of spaced fins 1118 for ensuring efficient thermal transfer between the heat pipe 1104 and the heat exchanger 1106.

[0195] As shown in Figure 11, the fins 1118 are embedded within the heat pipe at its second portion and extend into the heat exchanger 1106. In alternative examples, the fins are affixed to and extend away from a peripheral surface of the heat pipe and into the heat exchanger 1106. The fins may have any shape in cross-section (e.g., circles, squares, rectangles). The fins may be integrally formed on (i.e. , form part of) the envelope of the heat pipe (e.g., through casting or additive manufacturing techniques). Alternatively, the fins may be manufactured separately from the heat pipe and subsequently affixed onto the envelope (e.g., by welding or brazing).

[0196] In the example shown, the fins 1118 are evenly spaced but in other examples (not shown), the fins may have a non-uniform spacing.

[0197] As shown, the heat exchanger 1106 comprises a plurality of coolant lines 1130. Each coolant line extends in between two adjacent fins 1118. In an alternative example (not shown), the heat exchanger comprises a hollow pressure vessel into which the fins 1118 extend. Coolant may then flow through the inside of the pressure vessel and establish direct contact with the fins.

[0198] 37939900-1As the fins 1118 extend across the interface between the heat exchanger 1106 and the heat pipe 1104, they also advantageously provide a degree of mechanical stabilisation to the thermal management apparatus.

[0199] In some examples, the surface area of contact between the heat exchanger and the heat pipe (e.g., approximately the surface area of the cooling fins 1118 shown in Figure 11 is greater than the surface area of contact between the heat pipe and the component (e.g., approximately the surface area of attachment portions 922a-i shown in Figure 9A) by a factor N. N may be equal to or greater than, for example, 2, 5, or 10. As a result, the maximum temperature at the heat exchanger can be lowered considerably (as compared with the maximum temperature at the component), and the pumping requirements for the heat exchanger greatly reduced. This simplifies operation of the heat exchanger.

[0200] Figure 12A and 12B show plan views of, respectively, thermal management apparatuses 1200 and 1210 according to specific embodiments. In Figure 12A, thermal management apparatus 1200 includes a plurality of physically distinct component units 1202a-l in a castellated structure, a plurality of heat pipes 1204, and a heat exchanger 1206. In Figure 12B, thermal management apparatus 1210 includes a plurality of physically distinct component units 1212a-l in a castellated structure, a plurality of heat pipes 1214, and a plurality of heat exchangers 1216a-c. In these figures, the units 1202a-l, 1212a-l, each heat pipe 1204, 1214, and heat exchangers 1206, 1216a-c may be substantially as described in relation to Figures 9A, 9B, 10, and 11. The difference is that the apparatuses each include a plurality of heat pipes, which are operatively coupled either to a shared common heat exchanger (as in Figure 12A) or to respective individual heat exchangers (as in Figure 12B).

[0201] Referring in more detail to Figures 12A and 12B, the thermal management apparatuses 1200 and 1210 each include a plurality of heat pipes (respectively, 1204 and 1214) that are arranged into an array (respectively, 1208 and 1218), which may be termed a heat pipe array. In Figures 12A and 12B, there are three heat pipes shown, but it will be understood that the array can include any number of heat pipes. In Figures 12A and 12B, the heat pipes are also shown as rectangular in shape but it will be understood that other shapes (e.g., square) are possible.

[0202] 37939900-1Figure 12A and 12B show plan views of a thermal management apparatus 1210, 1220, according to an embodiment. Each thermal management apparatus 1210, 1220 includes a plurality of physically distinct units 1202a-l, a plurality of heat pipes 1204, 1214, and one or more heat exchangers 1206, 1216. The units 1202a-l, each heat pipe 1204, 1214, and heat exchangers 1206, 1216 may be substantially as described in relation to Figures 9A, 9B, 10, and 11. The difference is that the apparatuses include a plurality of heat pipes, which are either operatively coupled to a respective heat exchanger (as in Figure 12B) or to the same heat exchanger (as in Figure 12A).

[0203] Referring to more detail to Figures 12A and 12B, the thermal management apparatuses 1210, 1220 each include a plurality of heat pipes 1204, 1214, which are arranged into an array 1208, 1218 (herein heat pipe array). In Figures 12A and 12B, there are three heat pipes, but it will be understood that the array can have include any number of heat pipes. In Figures 12A and 12B, the heat pipes are also shown as rectangular in crosssection, but it will be understood that other shapes in cross-section (e.g., square) are possible.

[0204] There may or may not be a spacing between each row and / or column of the heat pipe array.

[0205] In Figure 12A, each heat pipe 1204 is operatively coupled to a common heat exchanger 1206. In Figure 12B, each heat pipe 1214 is operatively coupled to a respective one heat exchanger 1216a, 1216b, 1216c.

[0206] Each heat pipe 1204, 1214 in Figures 12A and 12B is associated with a respective set (denoted 1208a-c, 1218a-c) of units 1202a-l, 1212a-l. For simplicity, only sets 1208a and 1208c are labelled in Figure 12A, and only set 1218b is labelled in Figure 12B. The units included in each of these sets is shown by the dotted lines in the figures. For thermal management apparatuses 1210, 1220 that include a plurality of heat pipes, the component 1202, 1212 may comprise all of the respective sets of units. Each of the respective sets of units may comprise a multiplicity of units (e.g., more than 10, more than 30, or more than 50 units).

[0207] In some examples, the heat pipe array spans across a majority (e.g., more than 50%, 60%, 70%, 80%, or 90%) or all of a surface area of the component (e.g., of one side of

[0208] 37939900-1the component). For example, the heat pipe array can be arranged on any of the sides of the component. Typically, the component includes an impingement surface (e.g., a top side) for receiving an incident thermal flux and the heat pipe array is arranged in thermal contact with the surface of the component that opposes the impingement surface (e.g., its bottom side).

[0209] In the heat pipe arrays of Figure 12A and 12B, each heat pipe 1204, 1214 forms a row or column of the heat pipe array. The plurality of physically distinct units 1202a-l, 1212a-I are then collectively arranged into a rectilinear array, with each unit being substantially similar to one another in form (i.e. , in shape and size) and each set 1208a, 1208b, 1208c, 1218a, 1218b, 1218c of units forming a row or column of the rectilinear array. The rectilinear arrays in Figure 12A and 12B are rectangular but, alternatively, the array may be square, hexagonal, or triangular, for example. It will be understood that the component may comprise any number of the units in any arrangement.

[0210] The heat pipes (and if applicable their elongate channels) in Figures 12A to 12B are shown as being straight in plan view but, in other examples, some or all of the heat pipes may trace a curved or serpentine path. That is, some or all of the heat pipes and / or elongate channels may include one or more curved (e.g., ll-bend) sections. The component may also include a planar or curved surface.

[0211] Combinations of the thermal management apparatus 1210, 1220 shown in Figures 12A and 12B are possible. For example, the apparatus may include a plurality of heat exchangers, with a subset of those heat exchangers being associated with one respective heat pipe, and another subset being associated with a plurality of heat pipes.

[0212] Figure 13 is a cross-sectional view of a portion of the thermal management apparatus 600 from Figure 6, according to an embodiment. The cross-section shown comprises a component 602, a heat pipe 604 and heat exchanger 606a operatively coupled to the heat pipe. In Figure 13, the heat pipe is shown as including a wick 1308 but this is for illustrative purposes only. It will be understood that the heat pipe 604 may have a wick or may be wickless, and may be of any known type.

[0213] In use, a thermal flux profile 1310 is incident onto and strikes the component 602. The heat pipe 504 is therefore being operated in the first mode. An example thermal flux

[0214] 37939900-1profile 1310 is shown in Figure 13. The spatial distribution of the thermal flux (i.e., the thermal flux profile) that strikes the component is non-uniform (i.e., the magnitude of the thermal flux that strikes the incidence surface of the component varies with position across that surface) and the profile exhibits a peak or maximum. In some examples, the thermal flux profile is asymmetric and may be skewed in a direction towards heat exchanger 606a. The thermal energy caused to flow from the component 602 to the heat exchanger 606a is denoted in the figure by the two large arrows labelled A, B.

[0215] The thermal flux profile 1310 causes the component 602 to heat up in accordance with the thermal flux profile. That is, the thermal flux profile causes the component to heat up more at positions closer to the location of the peak of the thermal flux profile, as compared to positions that are further away from the peak. This generates a temperature hot spot 1312 within the component (the boundary of which is denoted by the vertical dotted lines in the figure). The size of the hot spot 1312 may be the full-width at halfmaximum, FWHM, of the temperature profile at the component. For asymmetric hot spots, an average FWHM can be used.

[0216] The heat pipe 604 is in thermal contact with the component 602. Heat pipe 604 therefore receives thermal energy from the component 602. The thermal flux profile received by the heat pipe (not shown in Figure 13) is, to a first approximation, similar in shape and size to profile 1310. That is, the heat pipe receives a thermal flux that varies with position (e.g., along its length) and which exhibits a peak.

[0217] In turn, the heat pipe 604 and the working fluid within the heat pipe is heated in accordance with the thermal flux that it locally receives. This causes a region of greatest evaporation of the working fluid (denoted in Figure 13 by the darkened region 1314 in wick 1308) the darkened region in wick 1308) to form within the heat pipe and / or at the envelope 1316 of the heat pipe. The region of greatest evaporation 1314 within the heat pipe and the hot spot 1312 within the component may be substantially co-located.

[0218] Heat pipes are sometimes referred to colloquially as “heat superconductors.” Heat is carried away rapidly from the evaporator region(s) of the heat pipe to the condenser region(s).

[0219] 37939900-1In the example of Figure 13, the evaporation rate of working fluid of the heat pipe 604 varies spatially across the mutual interface between the heat pipe 604 and the component 602 in accordance with the spatial distribution of the thermal flux that the heat pipe receives at that interface. The “heat superconductor” property of heat pipes makes heat pipe 604 effective at spreading out the heat from hot spot 1312 of the component (the exact location of which may not be known) so that the thermal flux across the mutual interface between the heat pipe and the heat exchanger can be made relatively uniform, and less than the maximum thermal flux received by the heat pipe in the vicinity of the hot spot(s) of the component In this way, the heat exchanger 606a need not be designed to accommodate the maximum thermal flux received at the component 602, as would otherwise be the case absent the heat-spreading capability of the heat pipe 604.

[0220] The heated working gas (i.e. , the vaporised working liquid) moves along the heat pipe 604 towards the heat exchanger 606a, where it condenses and releases its latent heat of condensation, which latent heat is extracted by the heat exchanger. In this way, thermal energy is transferred from the hot spot 1312 within the component 602 to the heat exchanger. Notably, while the thermal flux received by the component and heat pipe has a non-uniform spatial distribution, the thermal flux profile received by the heat exchanger is more spatially uniform because the working gas can spread out effectively at the heat exchanger before condensing. In some examples, the thermal energy or flux received by the heat exchanger may be substantially spatially uniform. This simplifies the operation of the heat exchanger.

[0221] In addition, the heat exchanger is less affected by variations in the spatial size and shape of the thermal flux profile 1310, the maximum temperature of the thermal flux profile, and / or the location of the hot spot 1312 on the component because the heat exchanger receives a thermal energy that is proportional to the total thermal flux received by the heat pipe from the component.

[0222] In some examples (not shown), there may be a plurality of hot spots at the component 602 and / or heat pipe, while the heat pipe is operated in the first mode. This may arise, for example, if the position of the peak in the thermal flux profile 1310 varies with time faster than the thermal management apparatus can remove the presence of the previous

[0223] 37939900-1hot spot. The heat spreading concept described above may apply to any one or each of these one or more hot spots.

[0224] Returning to Figure 13 in more detail, the component 602 comprises a plurality of physically distinct units (i.e., which are spatially separated from each other) illustratively shown as 1302a-1302i. For simplicity, only components 1302a and 1302i are labelled in the figure.

[0225] The physically distinct units 1302a-i are arranged in a castellated structure. It will be understood that the component may comprise any number of these units (e.g., more or fewer units than shown in the figure). In some examples, the component comprises a multiplicity of units (e.g., more than 10, more than 20, more than 30, or more than 50).

[0226] The units 1302a-i are described as being castellated as they form an outer surface that includes a series of spaced ridges or ridgeways 418. For clarity, only four of the eight ridgeways are labelled in the figure. The units may take various forms, for example, each unit may be a block, a tile, a plate, or a monoblock.

[0227] Each of the plurality of units 1302a-1302i is in thermal contact with the heat pipe 604 and affixed to the heat pipe at or along a first portion 1324 of the heat pipe. It will be appreciated that the heat pipe may be affixed either directly or indirectly to the plurality of units so long as the units and heat pipe remain in thermal contact. That is, the heat pipe and each unit may be in direct physical contact with one another, or they may be spatially separated from one another by one or more interlayers. Example interlayers include bonding materials between the heat pipe and component, such as solders, brazes, and adhesives. Alternatively, or in addition, the heat pipe and component may be bonded together via a further spacing interlayer which is then affixed to each of the component and heat pipe.

[0228] In the example shown, the first portion 1324 of heat pipe 604 includes a plurality of physically distinct attachment portions 1322a-i of the heat pipe 604. Each attachment portion 1322a-i attaches a corresponding unit 1302a-i of component 402 to heat pipe 404. For simplicity, only portions 1322b and 1322h are labelled in the figure. The first portion 1324 also includes portions of the heat pipe 604 situated in between adjacent units (e.g., between unit 1302a and 1302b), which portions are co-located with the

[0229] 37939900-1spaced ridgeways 1318. The first portion 1324 presents the surface area of contact or interface between the heat pipe 604 and the component 602 and through which thermal flux can pass between the component and the heat pipe.

[0230] The heat pipe 604 further includes a second portion 1326, which is operatively coupled to the heat exchanger 606a. The second portion presents the surface area of contact or interface between the heat pipe 604 and the heat exchanger 606a and through which thermal flux can pass between the heat pipe and the heat exchanger.

[0231] In use, the evaporator portion of the heat pipe 604 may include at least part of or all of the first portion 1324.

[0232] In use, the condenser portion of the heat pipe may include at least part of or all of the second portion 1326.

[0233] In use, an adiabatic portion of the heat pipe may include a third portion 1328 of the heat pipe that is interposed between the first and second portions. A thermally insulating jacket (not shown) may be arranged around the third portion of the heat pipe (to minimise heat transfer into and out of that portion). The thermal flux incident onto the third portion of the heat pipe is expected to be negligible in comparison with the thermal flux incident onto the first portion of the heat pipe.

[0234] In Figure 13, the adiabatic portion 1328 does not include any attachment portion to any one physically distinct unit 1302a-i. In practice, however, the adiabatic portion 1328 may include or encompass one or more of the physically distinct units 1302a-i (e.g., to units 1302h and 1302i). While the heat pipe is operated in the first mode, these units are functionally redundant, in the sense that they are not expected to receive or extract any thermal flux. However, the one or more physically distinct units (e.g., units 1302h and 1302i) may receive an incident thermal flux from profile 1310, if the profile is shifted towards the heat exchanger 606a. This may happen under abnormal or unexpected conditions. Advantageously, it also means that less precise alignment of the component 402 with respect to the expected thermal flux profile 1310 is required, thereby facilitating installation of the component.

[0235] 37939900-1In some examples, the heat pipe 604 is affixed to the component by an interlayer (not shown). The interlayer may be a solder, braze, ora separate material layer to be soldered or brazed between the body of the component and the heat pipe. Optionally, the coefficient of thermal expansion, CTE, for the interlayer is intermediate between the CTE of the envelope of the heat pipe and the CTE of the component. This reduces the induced thermal stresses in the apparatus during thermal loading.

[0236] In some examples, the heat pipe 604 and the component 602 are formed from the same material (e.g., a tungsten alloy). This advantageously avoids the need to design and / or select an interlayer with an intermediate CTE (which for some material combinations can be challenging).

[0237] The heat pipe 604 may be any known type of heat pipe. The heat pipe may include an elongate channel 1320, as shown in Figure 13. The elongate channel may be straight or include one or more bends. The bends may be made up of one or more straight and / or curved sections. The external shape of the heat pipe may be made suitable to the particular application or installation; e.g., it may be smooth and / or include undulations. The heat pipe and / or its channel may follow or trace a contour of a smooth external shape of the component (e.g., the plasma-facing surface of the component). The contour may comprise one or more straight line segments, curves, or a combination of straight-and curved-line segments. The external shape of the heat pipe may be tubular or planar, with any cross-sectional shape (e.g., square, rectangle, hexagon, circle, etc.).

[0238] In an alternative embodiment, as shown in Figure 14A, a heat pipe 604 is partially embedded within the component 1402. For simplicity, the component in Figure 14A includes five units 1402a-1402e rather than nine units, as depicted in Figure 13. It will be understood that the component may include any number (e.g., a multiplicity) of units.

[0239] In Figure 14A, the attachment portions between the heat pipe 604 and units 1402a-e are at least partially embedded within the units. If present, the interlayer is also embedded within the units.

[0240] In a variant of Figure 14A, the heat pipe 504 may, as shown in Figure 14B, pass completely through each of the units 1402a-e. Each of the units 1402a-e in Figure 14B has an opening (not visible in Figure 14B) through which the heat pipe passes. In Figure

[0241] 37939900-114B, the first portion of the heat pipe extends through each of the units of the component. The attachment portions between the heat pipe 604 and units 1402a-e are embedded within and / or extend through each of the units. If present, the interlayer is also embedded within and / or extends through each of the units.

[0242] A perspective view of three units 1402a-c from Figure 14B is shown in Figure 14C. As shown, the opening 1406 (through which the heat pipe 604 passes or extends) and the heat pipe 604 are circular in cross-section. Other shaped cross-sections, such as square, rectangular, are possible. Square and rectangular openings, which have sharp corners, may be prone to stress concentrations and fatigue failure. In some examples, the opening and heat pipe are rectangular or square in cross-section with rounded corners. The dotted lines in Figure 14A, Figure 14B, and Figure 14C show the hidden lines of the edges of the units.

[0243] It will be understood, when comparing Figure 6 with Figures 13 or 14A to 14C, that thermal flux, F (as depicted in Figure 6) may generally impinge onto the component 602 at an oblique angle. Accordingly, the thermal flux may not only strike the units 1302a-i, 1402a-e on their incidence or plasma-facing surfaces but also on their lower peripheral surfaces (or upper peripheral surface for the lower divertor 410 if present) that extend between the plasma-facing surfaces and the surfaces facing away from the plasma.

[0244] The units 1302a-i, 1402a-e may be positioned and shaped so as to prevent heat flux F from directly striking heat pipe 604. In some examples, the spacing of the units 902a-i is designed to be small enough to prevent the thermal flux F from striking the heat pipe 604 directly. Alternatively, or in addition, the plasma-facing surface of each unit may be angled or bevelled (in the toroidal or poloidal direction) to shadow the spaces between the units (e.g., the underlying heat pipe 604). That is, the units 1302a-i, 1402a-e may be shaped to be non-rectangular (e.g., trapezoidal or rhomboidal) in cross-section, with the plasma-facing surfaces angled so as to shade or shadow the spaces between the units 1302a-i, 1402a-e from thermal flux F. In yet further examples, the cross-section of the units 1302a-i, 1402a-e may be non-uniform to achieve a similar effect (e.g., conical in the toroidal or poloidal direction).

[0245] Figure 15A is a cross-sectional view of heat exchanger 606a from Figure 6, according to one embodiment. As shown, the heat 604 is arranged within the heat exchanger 606a.

[0246] 37939900-1For simplicity, only the second portion (e.g., the condenser portion) of the heat pipe 604 is shown and the first and third portions are omitted.

[0247] The heat exchanger 606a comprises a vessel 1508, the vessel comprising a closed end 1510, an open end 1512, a peripheral wall 1516 extending between the closed and open ends, and a plurality of spaced alignment fins 1514.

[0248] The heat pipe 604 comprises a plurality of baffles 1518, which extend outwardly relative to the heat pipe. The open end of the vessel is sealed closed against the periphery of the heat pipe so as to avoid loss of coolant from within the vessel during use.

[0249] In the configuration shown in Figure 15A, the second portion of the heat pipe 604 comprises a peripheral surface of the heat pipe contained within the vessel 1508 and the plurality of baffles 1518. In some examples, the combined surface area of the baffles and the peripheral surface of the heat pipe contained within the vessel (and thereby the total surface through which heat can be transferred to the heat exchanger 606) is greater than the surface area of contact between the heat pipe and the component 1302 (i.e. , at the first portion 1324, which includes attachment portions 1322a-i) or the surface area of the incidence surface of the component by a factor N, where N is greater than 1. For example, N may be equal to or greater than 2, 5, or 10. As a result, the thermal flux arriving at the heat exchanger can be lowered considerably (as compared with the thermal flux impinging upon the incidence surface of the component), and the pumping requirements for the heat exchanger therefore greatly reduced. Or put differently, the maximum temperature at the heat exchanger can be lowered considerably (as compared with the maximum temperature at the component), and the pumping requirements for the heat exchanger greatly reduced.

[0250] A perspective view of the heat pipe 604, with only five baffles 1518 for simplicity, is shown in Figure 15B. A cross-section along section A-A’, as shown by the dotted line in Figure 15A, is shown in Figure 15C. The baffles are shown as being circular in cross-section, although it will be understood that other shapes in cross-section are possible. The baffles may be embedded within, or otherwise affixed to the heat pipe (e.g., by welding or by brazing). In some examples (not shown), the baffles include one or more orifices to increase their surface area.

[0251] 37939900-1A cross-section along section B-B’, as shown by the dotted line in Figure 15A, is shown in Figure 15D. The alignment fins are shown as being generally rectangular in crosssection, with their ends shaped to conform to the curvature of the heat pipe 604 and the inner surface of the vessel wall 1508. It will be understood that the heat pipe 604 and the inner surface of the vessel may, in some examples, be substantially planar. The alignment fins may be integrally formed on (i.e. , form part of) the peripheral wall 1516 of the vessel 1508 (e.g., through casting or additive manufacturing techniques). Alternatively, the alignment fins may be manufactured separately from the vessel 1508 and subsequently affixed onto the peripheral wall (e.g., by welding or brazing).

[0252] Returning to Figure 15A, the baffles 1518 and alignment fins 1514 are spaced and arranged in size and shape such that, when the heat pipe is inserted into the vessel, the baffles align with and fit snugly (e.g., are flush with the fins) within the spaces between the fins. In the example shown, the fins and baffles are evenly spaced but in other examples (not shown), the fins and baffles may have corresponding non-uniform spacings.

[0253] The fins 1514 facilitate alignment of the heat pipe 604 within the vessel 1508, mechanically stabilise the heat pipe 604 within the vessel, and also promote efficient transfer of thermal energy away from the heat pipe (be that directly from the heat pipe envelope to the fin or via the baffle).

[0254] In use, a coolant (or, more generally, a heat exchange fluid), such a helium or carbon dioxide gas, is pumped through the vessel 1508 via a respective inlet and outlet (not shown in Figure 15A). As shown by comparing Figures 15C and 15D, the coolant is able to flow in a compartment formed between adjacent baffles 1518, and which comprises alignment fins 1514. This is further illustrated in a plan-view in Figures 17A and 17B. The coolant therefore generally flows in a direction transverse to the elongate channel of the heat pipe. The snug fit between the baffle and the vessel, as shown in Figure 15C, prevents or restricts coolant flow between adjacent compartments. This arrangement permits cooling of the heat pipe along the entire length of the evaporator portion.

[0255] In some examples, the heat pipe comprises a valve or a port 1520 through which the working fluid and charge (if present) can be removed or replenished, as needed. This is particularly useful in the fusion context because ions and / or gases, such as those

[0256] 37939900-1comprising hydrogen and / or helium, may diffuse and accumulate within the heat pipe, thereby affecting its performance over time. Periodic removal of these accumulated ions and / or gases and replenishment of the working fluid and NCG (if present) is desirable in this regard.

[0257] Baffles similar to the baffles 1518 shown for heat pipe 604 in Figure 15A may be included at the second portions of heat pipes 504 and 604 shown in any one of Figures 13 and 14A-14C. In addition, the heat exchanger 606a shown in Figure 13 may include the features (e.g., the alignment fins 1514) of heat exchanger 606a from Figure 15A.

[0258] In alternative embodiments, the heat pipe 604 comprises a plurality of cooling fins, which extend outwardly relative to the heat pipe but which, unlike baffles 1518, do not extend circumferentially around the heat pipe. In use, the heat exchange fluid is pumped through the vessel 1508 via the respective inlet and outlet and into contact with each of the plurality of cooling fins within a unitary compartment formed within the vessel 1508 (cf. the plurality of compartments defined by baffles 1518). In such embodiments, the vessel 608 may or may not comprise alignments fins 1514.

[0259] Turning to Figures 16A to 16C, plan views of, respectively, thermal management apparatuses 1600, 1610, 1620, according to specific embodiments, are shown.

[0260] Each of the thermal management apparatuses 1610, 1620, 1630 include a plurality of physically distinct component units (respectively 1602a-l, 1612a-l, 1622a-l in a castellated structure), one or more heat pipes (respectively, 1604, 1614, and 1624), and one or more heat exchangers (respectively 1606, 1616, 1626). The units 1602a-l, 1612a-l, 1622a-l, each heat pipe 1604, 1614, 1624, and each heat exchanger 1606, 1616, 1626 may be substantially as described in relation to Figures 13, 14A to C, 15A to D. The difference is that the heat pipe of Figure 16A includes a manifold section 1608, there are a plurality of heat pipes in Figure 16B and 16C, and the heat exchanger 1626 in Figure 16C is associated with a plurality of heat pipes 1624.

[0261] Referring in more detail to Figure 16A, the heat pipe 1604 includes a manifold section 1608, from which a plurality of heat pipe branches 1604a, 1604b, 1604c extend. Each of the heat pipe branches is operatively coupled to a respective one of a plurality of heat exchangers 1606 (denoted 1606a, 1606b, 1606c). The manifold section may be located

[0262] 37939900-1in the adiabatic portion (i.e., the third portion) of the heat pipe in proximity to the heat exchanger (e.g., adjacent to the second portion of the heat pipe). In Figure 16A, three heat exchangers and three heat pipe branches are shown, but it will be understood that there may be fewer or more heat exchangers and heat pipe branches. There may also be more heat pipe branches than heat exchangers (i.e., each or some of the heat exchangers may be shared amongst a plurality of heat pipe branches).

[0263] Turning to Figures 16B and 16C, the thermal management apparatuses 1610, 1620 each include a plurality of heat pipes arranged into an array (herein heat pipe array). In Figure 16B, there are three heat pipes 1614 arranged into an array, whereas in Figure 16C there are five heat pipes 1624 arranged into an array. It will be understood that the arrays can each include any number of heat pipes.

[0264] In Figure 16B, each heat pipe 1614 is operatively coupled to a respective one heat exchanger 1616a, 1616b, 1616c. In Figure 16C, each heat pipe 1624 is operatively coupled to a shared or common heat exchanger 1626.

[0265] Each heat pipe 1614, 1624 in Figures 16B and 16C is associated with a respective set (denoted 1618a-c, 1628a-e) of component units. For simplicity, only sets 1618a and 1618c are labelled in Figure 16, and only sets 1628a and 1628e are labelled in Figure 16C. For thermal management apparatuses 1610, 1620 that include a plurality of heat pipes 1614, 1624, the component 1302, 1402 may comprise all of the respective sets of units. Each of the respective sets of units may comprise a multiplicity of units (e.g., more than 10, more than 30, or more than 50 units).

[0266] In some examples, the heat pipe array spans across a majority (e.g., more than 50%, 60%, 70%, 80%, or 90%) or all of a surface area of the component (e.g., of one side). For example, the heat pipe array can be arranged on any of the sides of the component. Typically, the component includes an impingement surface (e.g., a top side) for receiving an incident thermal flux and the heat pipe array is arranged in thermal contact with the surface of the component that opposes the impingement surface (e.g., its bottom side).

[0267] In the heat pipe array of Figure 16B, each heat pipe 1614 forms a row or column of the heat pipe array. The plurality of physically distinct units 1612a-l are then collectively arranged into a rectilinear array, with each unit being substantially similar to one another

[0268] 37939900-1in form (i.e., in shape and size) and each set 1618a, 1618b, 1618c of units forming a row or column of the rectilinear array. The rectilinear array in Figure 16B is rectangular but, alternatively, the array may be square, hexagonal, or triangular, for example.

[0269] Turning to Figure 16C, each heat pipe 1624 also forms a row or column of the heat pipe array, with each heat pipe extending radially from a notional centre 1630. In the context of a plasma confinement device, the notional centre coincides with a central axis or core of the plasma confinement chamber of the plasma confinement device.

[0270] The heat pipes (and if applicable their elongate channels) in Figures 16A to 16C are shown as being straight in plan view but, in other examples, some or all of the heat pipes may trace a curved or serpentine path. That is, some or all of the heat pipes and / or elongate channels may include one or more curved (e.g., ll-bend) sections. The component may also include a planar or curved surface.

[0271] Combinations of the thermal management apparatus 1600, 1610, 1620 of Figures 16A to 16C are possible. For example, any one or more of the heat pipes in Figure 16B and 16C may include a manifold section from Figure 16A, and two or more (e.g., all) of heat pipe branches 1604a, 1604b, 1604c in Figure 16A may each be operatively coupled to a common heat exchanger.

[0272] Figure 17A is a cross-sectional view of a heat exchanger 1706 in plan view, showing a plurality of heat pipes 1704 arranged within the heat exchanger 1706. The heat pipes are arranged into an array. For simplicity, only the second portion of the heat pipe that is operatively coupled to the heat exchanger is shown and the first and third portions of the heat pipe are omitted. The heat exchanger and the second portion of the heat pipe may be substantially as described in relation to Figures 13, and 15A to 15 D.

[0273] As shown, the heat exchanger 1706 comprises a vessel 1708, an inlet manifold 1710 and an outlet manifold 1710. Each of the heat pipes is associated with a plurality of baffles 1718. The baffles are most apparent in Figure 17B, which is a perspective view of the heat pipe array from Figure 17A, with the heat exchanger omitted for simplicity.

[0274] As may be seen by comparing Figure 17A and Figure 17B, each of the baffles 1718 is shared amongst the plurality of heat pipes 1704 such that a compartment or channel

[0275] 37939900-11714 through which coolant may flow from the inlet manifold to the outlet manifold is formed between the baffles and the vessel 1708. One such compartment or channel 1712 is shown in Figure 17A and denoted by the dashed lines.

[0276] In operation, coolant (or, more generally, heat exchange fluid) is pumped into the vessel 1708 via inlet manifold 1710, into each of a plurality of compartments or channels 1714, and out via the outlet manifold 1712. The coolant passes into and through each compartment or channel in parallel. The coolant passes over each of the heat pipes 1704 in series in a direction transverse to the elongate channel of each heat pipe. The flow of coolant through one compartment 1714 is denoted by an arrow in the figure.

[0277] In some examples, the component (e.g., components 502, 602 from, respectively, Figures 5 and 6) may be a castellated armour or have a castellated armour.

[0278] In general, an armour, such as castellated armour, is more heat resistant than that which it protects and a component may be considered to be armour if that component protects itself, the heat pipe or another component from incident thermal energy or thermal flux.

[0279] The castellated armour may protect the component itself, the heat pipe, non-armoured parts of the component, or any combination of these, from incident heat flux and may also protect against radiation damage, for example, from high-energy neutrons emitted by a fusion plasma. In the example of Figure 4 and 5, the component is the upper divertor 420 (but could, alternatively, be the lower divertor 410). The units 902a-i, 1002a-e, 1102a-1102e, 1202a-l, 1212a-l, 1302a-i, 1602a-l, 1612a-l, 1622a-l, shown in Figures 9A to 9C, 10, 11, 12A-B, 13, and 16A-C are the castellated armour.

[0280] In general, an armour, such as castellated armour, is more heat resistant than that which it protects and a component may be considered to be armour if that component protects itself, the heat pipe or another component from incident thermal energy or thermal flux.

[0281] In some examples, a component is an armour if it is more heat resistant than the heat pipe. That is, the component is an armour if it can protect other parts of the apparatus (e.g., the envelope of the heat pipe) from the adverse effects (e.g., melting or softening) of an incident thermal flux. A component with greater heat resistance can withstand higher thermal fluxes without melting.

[0282] 37939900-1In some examples, the armour, such as a castellated armour, may act as a hydrogen isotope permeation barrier for the component or layer that it serves to protect.

[0283] A component may be heat resistant if the melting point of the material making up the component, at 0.1 MPa (1 bar), is greater than 1100°C (1373K), optionally greater than 1500°C (1773K), optionally greater than 2000°C (2273K).

[0284] The component may be heat resistant if it comprises a refractory metal, such as niobium, molybdenum, osmium, tantalum, tungsten or rhenium, or a refractory alloy comprising a mixture of one or more of these refractory metals.

[0285] Tungsten and tantalum are examples of materials that are resistant both to heat and to the high-energy neutrons emitted by, for example, a deuterium-tritium fusion plasma.

[0286] In some use cases, a low sputtering yield to incident particles (e.g., neutrons, protons) is also desirable. Materials with a lower sputtering yield erode less (i.e., lose less material), when subject to a given flux of incident particles. In the context of this disclosure, an armour has low sputtering yield, if its sputtering yield for neutrons or protons is less than either (1) the component which it protects (if the component has or comprises castellated or other armour for another component or for itself) or (2) the heat pipe (e.g., the envelope) which is affixed to the component.

[0287] Tungsten is an example of a material with a low sputtering yield. Other high atomic number metallic elements (>=40) also have acceptably low sputtering yields. In general, the component may include a metallic element as a main (i.e., the element with the highest atomic fraction) or sole (i.e., contains one element only, excluding trace elements) constituent, the metallic element having an atomic number greater than or equal to 40 to achieve a low sputtering yield. Example non-metallics that exhibit low sputtering yield include carbon fibre composites (e.g., for the divertor) and beryllium (e.g., for the first wall of the plasma confinement device).

[0288] As has already been noted, the disclosed heat pipe apparatus and methods are particularly useful for thermal management in systems that are expected to experience transient or cyclic thermal loads.

[0289] 37939900-1Example plasma confinement devices include: a magnetic confinement device, such as a tokamak (spherical or otherwise), a stellarator, a spheromak, a magnetic mirror machine, and a reversed field pinch device; inertial confinement devices, such as indirect drive, direct drive, fast ignition, magneto-inertial fusion devices, and Z-machines; pinch devices, such as a Z-pinch, theta-pinch, or screw-pinch device; and inertial electrostatic confinement devices, such as fusors or polywells. The disclosed apparatus forms part of such a plasma confinement device.

[0290] The component may then be any of: a shielding layer of the plasma confinement device; a plasma facing component; a divertor; a limiter; a first wall component; a breeder blanket; a portion thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

[0291] In a plasma confinement device, the thermal management apparatus may comprise any one or more of the following:

[0292] • a component (e.g., component shown in Figure 5, 6, 9A to 9C, 10, 11, 12A, 12B, 13, 14A to 14C, 16A to 16C) comprising a plurality of physically distinct tungsten units (e.g., blocks or tiles) arranged in a castellated formation. In a specific example, the width and length of each tungsten unit is 10 to 15 mm by 20 to 30 mm and the spacing between each of adjacent units is around 0.5 mm. The thickness of each tungsten unit is at least 5mm. The component may be any of: a shielding layer for the plasma confinement device; a plasma facing component, PFC; a divertor; a limiter; a first wall component; a breeder blanket; a portion thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

[0293] • one or more heat pipes, such as:

[0294] o a wick-containing heat pipe. The wick may be a multi-artery composite of silicon carbide, SiC. The envelope may be made from a material comprising tungsten, a vanadium, V, alloy, a niobium-zirconium alloy (such as Nb-1Zr wt%), a copper alloy (such as CuCrZr, e.g., 0.6-0.9wt% Cr, 0.07-0.15wt% Zr, Cu balance, or oxygen free Cu), or a steel (such as reduced activation ferritic martensitic, RAFM, steel). The working fluid may comprise or consist of: water, sodium, lithium, potassium, caesium, or a metallic alloy thereof, e.g., a sodium-potassium alloy, such as NaK.

[0295] 37939900-1Optionally, the heat pipe can be charged with a non-condensable gas, such as helium. The heat pipe can be a vapour chamber or conventional tubular type heat pipe.

[0296] o One or more wickless heat pipes. The heat pipe can be an oscillating or thermosiphon type heat pipe.

[0297] • The structural material for the heat exchanger may be a V-alloy, steel, or SiC.

[0298] • The coolant for the heat exchanger may be water, helium, or carbon dioxide.

[0299] Other coolants are, however, possible.

[0300] SiC is a particularly useful wick for plasma confinement devices, as it exhibits excellent thermal conductivity (comparable to brass) but poor electrical conductivity (it is classified as a semiconductor). The low electrical conductivity of the SiC reduces or suppresses magnetohydrodynamic, MHD, effects, which act on electrically conductive fluids (e.g., liquid metals) in a plasma confinement devices, when subject to an external magnetic field.

[0301] NaK is particularly beneficial as a working fluid for the heat pipe in a plasma confinement device because it is operative at room temperature Advantageously, such a heat pipe would not require heating up before use (i.e. , to melt any solid charge).

[0302] One specific use case of the proposed thermal management method is to remove tritium from lithium-containing components, e.g., by melting, evaporating, or otherwise separating the lithium-containing part and collecting any released tritium gas. In a specific example, the method of removing tritium may be carried out in-situ within a plasma confinement device. The minimum allowable temperature may then be greater than the liquidus temperature of the lithium-containing component at operating pressure.

[0303] Another specific use case is to maintain the temperature of a tungsten or tungsten-containing component above a minimum allowable temperature of, for example, 600 to 700°C between plasma pulses. In a specific example, the tungsten or tungsten-containing component is a plasma facing component for or in a plasma confinement device (e.g., a divertor block, monoblock, plate, or tile). Maintaining the divertor at elevated temperatures between pulses reduces the magnitude of the thermal stresses induced when the pulse is ignited. As has already been noted, the coolant storage unit

[0304] 37939900-1520, 620 may advantageously be used to provide thermal energy to the divertor between pulses to save having to heat up the coolant of the heat exchanger afresh.

[0305] More generally, the charge or working fluid can be any of: water or a metal comprising an alkali metal, such as: lithium, sodium, potassium, caesium, or a mixture thereof.

[0306] The heat pipe may be operative within a temperature range of 150 to 300°C (423 to 573K) for water, from around 400°C (673K), for caesium, and up to around 1300°C for alkali metal mixtures. In some examples, the heat pipe is operative from room temperature (typically 20°C to 25°C) to 700°C, 1000°C, or 1300°C. It will be understood that these temperature ranges are not exhaustive: the heat pipe may be operative at temperatures down to its freezing point at the given pressure.

[0307] Figure 18 is a schematic illustration of a power generation system 1800. The system includes a heat source 1802, the thermal management apparatus 500, 600, 1100, 1200, 1210, 1600, 1610, 1620 described above in relation to any of the foregoing embodiments, which is thermally coupled to the heat source, and a turbine 1806. Thermal management apparatus is labelled 500, 600 in Figure 18 for clarity. The turbine is operatively coupled to one of the one or more heat exchangers of the apparatus. In general, there may be a plurality of turbines operatively coupled to each heat exchanger. In some examples, the system 1800 is or includes any one of the plasma confinement devices referred to above.

[0308] Figure 19 is a flow diagram of a power generation method 1900 carried out by power generation system 1800.

[0309] In step 1902, one or more heat pipes receive at least a portion of a thermal energy emitted by a heat source. In some examples, the heat source may be plasma, such as a nuclear fusion plasma, which impinges upon (i.e. , strikes) an impingement surface of the component (e.g., a divertor in a tokamak) at a strike point. The plasma may impinge upon the impingement surface of the component at an oblique or perpendicular angle thereto.

[0310] Prior to or contemporaneously with step 1902, plasma operating parameters may be controlled or adjusted to generate or sustain a plasma within the plasma confinement

[0311] 37939900-1device. The strike point of the plasma on the component may vary continuously with time. As a result, one or more hot spots may develop at the component.

[0312] In step 1904, at least a portion of the received thermal energy is conveyed along or through each or the heat pipe (e.g., along or through the elongate channel of each or the heat pipe) and into the or each heat exchanger. Coolant carried by the heat exchanger is heated up in step 1904.

[0313] In step 1906, a turbine is driven to turn by the flow of the heated coolant in order to generate electrical power.

[0314] Although the invention has been described in terms of specific embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated as falling with the scope of the appended claims. Each feature disclosed or illustrated in the present application may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein. It will be understood that the numbering in the method flow diagrams is not intended to impose a strict ordering of those steps.

[0315] Certain aspects of the invention are summarised by the following numbered clauses:

[0316] 1. In a phase change-mediated heat pipe in thermal contact with a component for a plasma confinement device, a method comprising conveying heat through the heat pipe to the component, thereby heating the component.

[0317] 2. The method of clause 1 , further comprising receiving heat into the heat pipe, and wherein the conveying comprises conveying at least a portion of the received heat through the heat pipe to the component.

[0318] 3. The method of clause 2 wherein the heat pipe is operatively coupled to a heat source, and wherein the receiving comprises receiving heat from the heat source into the heat pipe.

[0319] 37939900-14. In a phase change-mediated heat pipe in thermal contact with a component for a plasma confinement device, a method comprising:

[0320] activating a mode of operation of the heat pipe from among a plurality of available modes of operation including a forward mode and a reverse mode;

[0321] with the forward mode activated, conveying heat away from the component through the heat pipe, thereby cooling the component; and with the reverse mode activated, conveying heat through the heat pipe to the component as recited in clause 1.

[0322] 5. The method of clause 4 and further comprising, with the forward mode activated, transferring at least a portion of the heat conveyed away from the component out of the heat pipe to a heat exchanger.

[0323] 6. The method of clause 4 wherein the heat pipe is operatively coupled to a heat exchanger, and further comprising:

[0324] with the forward mode activated, transferring at least a portion of the heat conveyed away from the component out of the heat pipe to the heat exchanger;

[0325] with the reverse mode activated, receiving heat into the heat pipe from the heat exchanger and conveying at least a portion of the received heat through the heat pipe to the component.

[0326] 7. The method of clause 1 and further comprising continuing to perform the conveying to heat the component at least until the component reaches a specified temperature.

[0327] 8. The method of clause 7 wherein the specified temperature is a temperature sufficient to liquify a metal so as to facilitate a flow thereof on a surface of the component.

[0328] 9. The method of clause 8 wherein the metal comprises lithium.

[0329] 10. The method of clause 7 wherein the component is tritiated and wherein the specified temperature is a temperature sufficient to facilitate a release of tritium

[0330] 37939900-1from the tritiated component.

[0331] 11. Apparatus comprising:

[0332] a component for a plasma confinement device;

[0333] a heat source; and

[0334] a phase-change mediated heat pipe, in thermal contact with the component and operatively coupled to the heat source.

[0335] 12. The apparatus of clause 11 wherein the heat source comprises a heat exchanger.

[0336] 13. The apparatus of clause 12 and further comprising a control to select an active mode of operation of the apparatus from a plurality of available modes, the available modes including a first (or “forward”) mode of operation wherein the heat pipe conveys heat away from the component to the heat exchanger and a second (or “reverse”) mode of operation wherein the heat pipe conveys heat from the heat exchanger to the component.

[0337] 14. The apparatus of clause 13 wherein the heat exchanger has a heat intake and a heat exhaust, and wherein:

[0338] in the forward mode of operation, at least a portion of heat conveyed away from the component through the heat pipe to the heat exchanger is exhausted by the heat exchanger through the heat exhaust; and in the reverse mode of operation, heat is accepted into the heat exchanger through the heat intake and at least a portion of heat thus accepted is conveyed through the heat pipe to the component.

[0339] 15. The apparatus of clause 14 wherein the heat exchanger includes:

[0340] a fluid inlet;

[0341] a fluid outlet; and

[0342] one or more channels, coupled to the inlet and outlet, to support flow through the heat exchanger of a heat exchange fluid;

[0343] and wherein the heat intake comprises the fluid inlet and the heat exhaust comprises the fluid outlet.

[0344] 37939900-116. The apparatus of clause 15 and further comprising a heat exchange fluid comprising one of water, a molten metal, a molten salt, a gas, an inert gas, or carbon dioxide.

[0345] 17. The apparatus of clause 11 wherein:

[0346] the heat pipe has first and second portions;

[0347] the heat pipe is attached to and in thermal contact with the component in a vicinity of the first portion; and

[0348] the heat pipe is operatively coupled to the heat source in a vicinity of the second portion.

[0349] 18. The apparatus of clause 11 wherein the component is one of a plasma-facing component, a divertor, a limiter, a first wall, a shield, a breeder blanket, a portion or segment of any of these, armour or an armour part for any of these or for a portion or segment thereof, or a thermal management component for any of the foregoing.

[0350] 19. The apparatus of clause 11 wherein the component has armour.

[0351] 20. The apparatus of clause 19 wherein the armour is wholly or partially integrated into the component.

[0352] 21. The apparatus of clause 19 wherein the armour is castellated.

[0353] 22. The apparatus of clause 19 wherein the armour has a surface configured to facilitate a flow of liquid metal thereon.

[0354] 23. The apparatus of clause 19 wherein the armour comprises a layer and wherein the heat pipe has a long axis substantially parallel to the layer.

[0355] 24. The apparatus of clause 11 wherein the heat pipe is attached to the component.

[0356] 25. The apparatus of clause 24 wherein an interlayer is disposed between the heat pipe and the component.

[0357] 37939900-126. The apparatus of clause 11 and further comprising one or more additional phase-change mediated heat pipes each in thermal contact with the component and operatively coupled to the heat source.

[0358] 27. A system comprising the apparatus of clause 11 and a plasma confinement device wherein the component is disposed.

[0359] 28. The system of clause 25 wherein the plasma confinement device is a tokamak or a stellarator.

[0360] 29. A phase-change mediated heat pipe, in thermal contact with a component for a plasma confinement device, operable to convey heat to the component.

[0361] Further aspects of the invention are summarised by the following numbered clauses:

[0362] 101. A phase-transition mediated heat pipe partially embedded in a castellated armour. Put differently, the heat pipe may comprise a castellated armour.

[0363] 102. The heat pipe of clause 101 wherein a first portion of the heat pipe passes through the armour and a further portion (e.g., the second or third portion as described above) of the heat pipe extends away from the armour.

[0364] 103. The heat pipe of clause 102 wherein the castellated armour comprises a plurality of monoblocks arrayed along a length of the first portion of the heat pipe.

[0365] 104. The heat pipe of clause 102 wherein the heat pipe is operatively coupled to a heat exchanger in a vicinity of the second portion of the heat pipe.

[0366] 105. Apparatus comprising a plurality of the heat pipes of clause 101 and a component for a plasma confinement device (for nuclear fusion), wherein the component has armour comprising the armour wherein the heat pipes are partially embedded.

[0367] 106. The apparatus of clause 105 wherein the armour is wholly or partially integrated into the component.

[0368] 37939900-1107. The apparatus of clause 105 wherein the component is for a plasma confinement device having, at least approximately, a toroidal, spherical, circular, or other geometric symmetry around a central axis, and wherein each of the heat pipes has a long axis disposed in a direction substantially radial with respect to a point on the central axis.

[0369] 108. The apparatus of clause 105 wherein the component has a plasma-facing surface and wherein each of the heat pipes has a long axis disposed in a direction substantially parallel to a smooth surface approximating the plasma-facing surfaces.

[0370] 109. The apparatus of clause 108 wherein the plasma-facing surface of the component is coincident with a surface of the armour.

[0371] 110. A system comprising the apparatus of clause 105 and a plasma confinement device wherein the component is disposed.

[0372] 111. The system of clause 110 wherein the component, as disposed in the plasma confinement device, has a surface facing a plasma confinement region of the plasma device, and wherein each of the heat pipes has a long axis substantially parallel to a smooth surface approximating the surface of the component facing the plasma confinement region of the plasma device.

[0373] 112. Apparatus comprising:

[0374] a heat exchanger; and

[0375] a plurality of the heat pipes of clause 101 disposed in an array or manifold and operatively coupled to the heat exchanger.

[0376] 113. In a system comprising the apparatus of clause 105 operatively coupled to a heat exchanger and further comprising a plasma confinement device wherein the component is disposed, a thermal management method comprising:

[0377] receiving heat at the component from a plasma contained by the plasma confinement device during operation of the system;

[0378] conveying at least a portion of the received heat to the heat exchanger through the heat pipes; and

[0379] exhausting at least a portion of the conveyed heat away from the heat exchanger.

[0380] 37939900-1114. The method of clause 113 wherein the armour is of a material having a brittle-ductile transition temperature and a re-crystallisation temperature, and wherein during performance of the method the armour is substantially maintained at a temperature above the brittle-ductile transition temperature of the armour material and below the recrystallisation temperature of the armour material.

[0381] 115. The method of clause 113 wherein, in the apparatus of clause 105, the component has a plasma-facing surface and each of the heat pipes has a long axis disposed in a direction substantially parallel to a smooth surface approximating the plasma-facing surface, and wherein receiving heat at the component comprises receiving, from a plasma contained by the plasma confinement device during operation of the system, heat from a heat flux incident on the plasma-facing surface of the component.

[0382] 116. The apparatus of clause 105 wherein the component is one of a plasma-facing component, a divertor, a limiter, a first wall, a shield, a breeder blanket, a portion or segment of any of these, an armour part for any of these or for a portion or segment thereof, or a thermal management component for any of the foregoing.

[0383] 117. The heat pipe of clause 101 wherein the armour comprises a refractory metal or an alloy of a refractory metal.

[0384] 118. The heat pipe of clause 117 wherein the refractory metal comprises tungsten.

[0385] 119. The heat pipe of clause 101 wherein the heat pipe has a liquid metal working fluid comprising one or more of caesium, potassium, sodium, NaK, and lithium.

[0386] 120. The apparatus of clause 111 wherein the plasma confinement device is one of a magnetic confinement device, a tokamak, a stellarator, a spheromak, a mirror machine, a field-reversed configuration device, or a Z-pinch device.

[0387] 121. The apparatus of clause 105 and further comprising a heat exchanger operatively coupled to a plurality of the heat pipes.

[0388] 37939900-1122. The heat pipe of clause 102 wherein the first portion of the heat pipe is proximal to a first end of the heat pipe and the second portion of the heat pipe is proximal to a second, opposite end of the heat pipe.

[0389] 123. A method of operating the heat pipe of clause 102 wherein the heat pipe is reversible, comprising:

[0390] activating an operating mode of the heat pipe from among a plurality of operating modes including a forward mode and a reverse mode;

[0391] in the forward mode, conveying heat through the heat pipe from the first portion of the heat pipe to the second portion of the heat pipe; and in the reverse mode, conveying heat from the second portion of the heat pipe to the first portion of the heat pipe.

[0392] 124. The apparatus of clause 105 and further comprising a control to select an active mode of operation of the apparatus from a plurality of available modes, the available modes of operation including a first (or “forward”) mode wherein the heat pipes convey heat away from the armour of the component and a second (or “reverse”) mode wherein the heat pipes convey heat to the armour of the component.

[0393] 125. In the apparatus of clause 124, a method of de-tritiating the armour of the component, comprising:

[0394] activating the reverse mode;

[0395] with the reverse mode activated,

[0396] providing heat from a heat source to the heat pipes, and conveying at least a portion of the provided heat through the heat pipes to the armour;

[0397] and

[0398] continuing to perform the providing and conveying to heat the armour until the armour reaches a temperature sufficient to facilitate a release of tritium therefrom.

[0399] 126. A system comprising:

[0400] the apparatus of clause 104, wherein the heat exchanger is configured to carry a flow of coolant (or heat exchange fluid) comprising a gas; and

[0401] 37939900-1a power-producing subsystem, operatively coupled to the heat exchanger, comprising a turbine configured to be driven by the gas.

[0402] 127. The heat pipe of clause 102 wherein a first portion of the heat pipe passes through the armour and the or each further portions (e.g., the second or the third portion as described above) of the heat pipe extend away from the armour.

[0403] 128. Apparatus comprising the heat pipe of clause 127 and first and second heat exchangers operatively coupled to the heat pipe, respectively, in vicinities of the second portions of the heat pipe (e.g., at either longitudinal end of the heat pipe).

[0404] 129. In the heat pipe of clause 102, a method comprising:

[0405] receiving heat from the castellated armour into the heat pipe in a vicinity of the first portion of the heat pipe; and

[0406] conveying at least some of the received heat through the heat pipe to the second portion of the heat pipe.

[0407] 130. A method for thermal management of a component for a plasma confinement device, the component having castellated armour comprising the armour of the heat pipe of clause 102, the method comprising:

[0408] receiving, from the armour of the heat pipe, an input non-uniform heat flux into the first portion of the heat pipe; and

[0409] providing a substantially uniform output heat flux out of the second portion of the heat pipe.

[0410] Yet further aspects of the present invention are summarised by the following numbered clauses:

[0411] 201. A phase-change mediated heat pipe attached to and in thermal contact with a plurality of physically distinct pieces of a castellated armour, the heat pipe having first and second heat transfer surfaces disposed on opposite sides of a long axis of the heat pipe, at least one of the first and second surfaces or a mean surface therebetween being substantially parallel to the long axis, the heat pipe being attached to the armour in a vicinity of the first surface.

[0412] 37939900-1202. The heat pipe of clause 201 operably coupled to a heat exchanger in a vicinity of the second surface.

[0413] 203. The heat pipe of clause 201 wherein the heat pipe comprises an envelope and a wick, the envelope including the first and second surfaces, the wick running along the long axis.

[0414] 204. The heat pipe of clause 201 wherein the pieces are substantially similar to one another.

[0415] 205. The heat pipe of clause 201 wherein the pieces are disposed in a rectilinear array on the first surface.

[0416] 206. The heat pipe of clause 205 wherein the rectilinear array is one of a rectangular array, a hexagonal array, or a triangular array.

[0417] 207. A method comprising:

[0418] receiving heat into the heat pipe of clause 201 from the armour at the first surface; and

[0419] distributing at least a portion of the received heat substantially uniformly over the second surface.

[0420] 208. The method of clause 207 wherein the receiving comprises receiving heat distributed non uniformly over the first surface.

[0421] 209. The method of clause 208 wherein the receiving comprises receiving heat concentrated in a vicinity of a point on the first surface.

[0422] 210. The method of clause 207 wherein the distributing comprises conveying the portion of the received heat through the heat pipe from the first surface to the second surface.

[0423] 211. The method of clause 207 and further comprising transferring at least a portion of the conveyed heat to a heat exchanger operatively coupled to the heat pipe at the second surface.

[0424] 37939900-1212. The method of clause 211 wherein transferring comprises transferring the heat in a direction substantially perpendicular to the long axis of the heat pipe.

[0425] 213. The method of clause 212 wherein the transferring comprises transferring a substantially uniform heat flux across the second surface.

[0426] 214. The method of clause 213 wherein the receiving comprises receiving a first heat flux into the heat pipe at the first surface from a portion of the armour in a vicinity of a point on the first surface; and the transferring comprises transferring a second heat flux out of the heat pipe at the second surface, the second heat flux having a lower power per unit area than the first heat flux.

[0427] 215. In an apparatus comprising the heat pipe of clause 201 and a plasma confinement device (for nuclear fusion) comprising a divertor having armour comprising the armour attached to the heat pipe, the method of clause 214 wherein the receiving comprises receiving the first heat flux from a portion of the armour in a vicinity of a strike point of the divertor during operation of the plasma confinement device.

[0428] 216. Apparatus comprising a plurality of the heat pipes of clause 201 and a component for a plasma confinement device (for nuclear fusion), wherein the component has armour comprising the armour attached to the heat pipes.

[0429] 217. The apparatus of clause 216 wherein the armour is wholly or partially integrated into the component.

[0430] 218. The apparatus of clause 216 and further comprising a heat exchanger operably coupled to the heat pipes at the second surfaces thereof.

[0431] 219. In a system comprising the apparatus of clause 218 and further comprising a plasma confinement device wherein the component is disposed, a thermal management method comprising:

[0432] receiving heat at the component from a plasma contained by the plasma confinement device during operation of the system;

[0433] 37939900-1conveying at least a portion of the received heat to the heat exchanger through the heat pipes; and

[0434] exhausting at least a portion of the conveyed heat away from the heat exchanger.

[0435] 220. A method of operating the heat pipe of clause 201 wherein the heat pipe is reversible, comprising:

[0436] activating an operating mode of the heat pipe from among a plurality of operating modes including a forward mode and a reverse mode;

[0437] in the forward mode, receiving heat at the first surface and distributing at least a portion of the heat over the second surface; and

[0438] in the reverse mode, conveying heat from the second surface to the first surface.

[0439] 221. The apparatus of clause 216 and further comprising a control to select an active mode of operation of the apparatus from a plurality of available modes, the available modes of operation including a first (or “forward”) mode wherein the heat pipes convey heat away from the armour of the component and a second (or “reverse”) mode wherein the heat pipes convey heat to the armour of the component.

[0440] 222. In the apparatus of clause 221 , a method of de-tritiating the armour of the component, comprising:

[0441] activating the reverse mode;

[0442] with the reverse mode activated,

[0443] providing heat from a heat source to the heat pipes, and conveying at least a portion of the provided heat through the heat pipes to the armour;

[0444] and

[0445] continuing to perform the providing and conveying to heat the armour until the armour reaches a temperature sufficient to facilitate a release of tritium therefrom.

[0446] 37939900-1

Claims

66CLAIMS:

1. A thermal management method comprising:operating a heat pipe in a first mode to extract thermal energy from a component of a plasma confinement device, the component being thermally coupled to the heat pipe; andoperating the heat pipe in a second mode to convey thermal energy to the component.

2. A thermal management method according to claim 1, wherein the component is disposed in the plasma confinement device and wherein:the heat pipe is operated in the first mode during a presence of plasma in the plasma confinement device; andthe heat pipe is operated in the second mode during an absence of plasma from the plasma confinement device.

3. A thermal management method according to claims 1 or 2, wherein:the heat pipe is operated in the first mode while a temperature of, or associated with, the component is greater than or equal to a first threshold temperature; and the heat pipe is operated in the second mode while the temperature of, or associated with, the component is less than or equal to a second threshold temperature, the second threshold temperature being less than or equal to the first threshold temperature.

4. The thermal management method according to claim 3, when dependent on claim 2, wherein:the first and second threshold temperatures are different from one another; and the heat pipe is operated in the first mode during an absence of plasma from the plasma confinement device while the temperature of, or associated with, the component is between the first and second threshold temperatures.

5. A thermal management method according to any one of the preceding claims, wherein the heat pipe alternates between operating in the first mode and operating in the second mode.37939900-1676. A thermal management method according to any one of the preceding claims, wherein the component is disposed in the plasma confinement device and further comprising:changing from operating the heat pipe in the first mode to operating the heat pipe in the second mode contemporaneously with or in response to an end of a plasma pulse in the plasma confinement device; andchanging from operating the heat pipe in the second mode to operating the heat pipe in the first mode contemporaneously with or in anticipation of a start of a plasma pulse in the plasma confinement device.

7. A thermal management method according to any one of the preceding claims, wherein the component is disposed in the plasma confinement device and further comprising:changing from operating the heat pipe in the first mode to operating the heat pipe in the second mode in response to a loss or disruption of a plasma in the plasma confinement device.

8. A thermal management method according to any one of the preceding claims, further comprising:determining a temperature of, or associated with, the component; conditional upon the temperature thus determined is being greater than or equal to a maximum allowable temperature:operating the heat pipe in the first mode to decrease the temperature of, or associated with, the component.

9. A thermal management method according to any one of the preceding claims, further comprising:determining a temperature of, or associated with, the component; conditional upon the temperature thus determined being less than or equal to a minimum allowable temperature:operating the heat pipe in the second mode to increase or maintain the temperature of, or associated with, the component.

10. A thermal management method according to any one of the preceding claims, wherein:operating the heat pipe in the first mode comprises conveying thermal energy from the component to a heat exchanger via the heat pipe; and37939900-168operating the heat pipe in the second mode comprises conveying thermal energy from the heat exchanger to the component via the heat pipe.

11. A thermal management method according to claim 10, and further comprising: controlling one or more operating parameters of the heat exchanger.

12. A thermal management method according to any one of claims 10 to 11, further comprising:while operating the heat pipe in the second mode, modifying one or more operating parameters of the heat exchanger to reduce the thermal energy conveyed to the component to allow the component to passively cool.

13. A thermal management method according to any one of claims 10 to 11, further comprising:determining a temperature of, or associated with, the component; and conditional upon the temperature thus determined being greater than or equal to a maximum allowable temperature:modifying one or more operating parameters of the heat exchanger to allow the component to passively cool.

14. A thermal management method according to any one of claims 11 to 13, wherein the one or more operating parameters include any one or more of: a temperature of a coolant or heat exchange fluid in the heat exchanger; a flow rate of a coolant or heat exchange fluid through the heat exchanger; and a pressure of a coolant or heat exchange fluid in the heat exchanger.

15. A thermal management method according to claims 8, 9, or 13, wherein determining a temperature of, or associated with, the component, comprises:determining a spatial distribution of temperatures across the component; and selecting a temperature from said distribution.

16. A thermal management method according to any one of the preceding claims, wherein the heat pipe is one of a plurality of heat pipes, each of the heat pipes being affixed to the component at a corresponding attachment portion of the component, and wherein:37939900-169operating the heat pipe in the first mode comprises operating two or more of the heat pipes of the plurality in the first mode; andoperating the heat pipes in the second mode comprises operating two or more of the heat pipes of the plurality in the second mode.

17. A thermal management method according to claim 16, wherein the heat pipes of the plurality are arranged to form an array, the array spanning across the component.

18. A thermal management method according to claim 17, wherein each heat pipe of the plurality alternates between operating in the first mode and operating in the second mode.

19. A thermal management method according to claim 18, wherein each heat pipe of the plurality alternates between the first and second operating modes contemporaneously with respect to each other heat pipe of the plurality.

20. A thermal management method according to any one of claims 16 to 19, wherein each heat pipe of the plurality is operatively coupled to a heat exchanger, and wherein:operating each heat pipe in the first mode comprises conveying thermal energy from the component to the heat exchanger via said heat pipe; andoperating each heat pipe in the second mode comprises conveying thermal energy from the heat exchanger to the component via said heat pipe.

21. A thermal management method according to any one of claims 16 to 19, wherein each heat pipe of the plurality is operatively coupled to at least one of a plurality of heat exchangers, and wherein:operating each heat pipe in the first mode comprises conveying thermal energy from the component to at least one of the heat exchangers via said heat pipe; and operating each heat pipe in the second mode comprises conveying thermal energy from said at least one heat exchanger to the component via said heat pipe.

22. A thermal management method according to any one of the preceding claims, wherein a melting point of the component, at 0.1 MPa, is greater than 1100°C.37939900-17023. A thermal management method according to any one of the preceding claims, wherein a main constituent of a material of the component is a metallic element, the metallic element having an atomic number greater than or equal to 40.

24. A thermal management method according to any one of the preceding claims, wherein the component comprises a refractory metal or an alloy of a refractory metal.

25. A thermal management method according to claim 24, wherein the refractory metal comprises tungsten.

26. A thermal management method according to claim 9 or any one of claims 10 to 25, when dependent on claim 9, wherein the minimum allowable temperature is in a range of 600 to 700°C.

27. A thermal management method according to claim 9 or any one of claims 10 to 26, when dependent on claim 9, wherein the component comprises lithium and the minimum allowable temperature is greater than a liquidus temperature of the lithium-containing part of the component at operating pressure.

28. A thermal management method according to claim 27, further comprising collecting tritium released from the component while the or each heat pipe is operating in the second mode.

29. A thermal management method according to any one of the preceding claims, wherein, in the first mode, the or each heat pipe is operated at temperatures in excess of 200°C.

30. A thermal management method according to any one of the preceding claims, wherein the component is or has a castellated armour.

31. A thermal management method according to any one of the preceding claims, wherein the component comprises a plurality of physically distinct units.

32. A thermal management method according to claim 31, wherein said units are arranged to form a castellated structure.37939900-17133. A thermal management method according to any one of the preceding claims, wherein the or each heat pipe has a working fluid comprising: water, or, any one of lithium, sodium, potassium, a sodium-potassium alloy, caesium, or any mixture of the foregoing metals.

34. A thermal management method according to claim any one of the preceding claims, wherein the component is any of: a shielding layer of the plasma confinement device; a plasma facing component; a divertor; a limiter; a first wall component; a breeder blanket; a portion thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

35. A thermal management method according to any one of the preceding claims, wherein the plasma confinement device is any of: a magnetic confinement device; a tokamak; a stellarator; a spheromak; a spherical tokamak; a magnetic mirror machine; a reversed field pinch device; a Z-machine; a Z-pinch device; a theta-pinch device; a screw pinch device; a fusor; or a polywell.

36. A thermal management method according to any one of the preceding claims, wherein a coolant or heat exchange fluid through the or each heat exchanger comprises one or more of: water, a molten metal, a molten salt, an inert gas, or carbon dioxide.

37. A thermal management method according to any one of the preceding claims, wherein the component is disposed in the plasma confinement device and further comprising:operating the plasma confinement device in a pulsed or cyclic mode, wherein plasma is, by turns, present in and absent from the plasma confinement device;during a presence of plasma in the plasma confinement device, operating the heat pipe in the first mode; andduring an absence of plasma from the plasma confinement device, switching from operating the heat pipe in the first mode to operating the heat pipe in the second mode.

38. An apparatus, comprising:one or more heat pipes;a component to which the or each heat pipe is thermally coupled;37939900-1one or more heat exchangers operatively coupled to the one or more heat pipes; anda controller coupled to the or each heat exchanger and being operable to cause the apparatus to perform the method of any one of claims 1 to 37.37939900-1

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