Enhanced fuel recovery for fusion reactors and related issues

Abstract

A cryopump (100) for recovering fuel from the exhaust gas of a nuclear fusion reactor (10) is described. The cryopump (100) includes a chamber configured to receive the gas, a first panel (104) disposed in the chamber and cooled to a first temperature, the first temperature being greater than 20 Kelvin, a second panel (106) disposed in the chamber and cooled to a second temperature, the second temperature being in the range of 10 Kelvin to 20 Kelvin, and a valve configured to isolate the second panel from the first panel. The example cryopump (100) enables faster fuel recovery for the reactor, reducing energy costs of operation.

Description

[Technical Field]

[0001] The present disclosure relates generally to techniques for treating exhaust gases from nuclear fusion reactors, such as tokamaks, to enable rapid deuterium and tritium recovery and recycling, and more particularly to a multi-stage cryopump for use in such techniques. [Background technology]

[0002] Recently, fusion reactors that rely on magnetic confinement, primarily those designed on the tokamak principle, use fusion fuel containing a mixture of deuterium and tritium (i.e., hydrogen isotopes). A by-product of the fusion process is helium, which must be extracted from the reactor by appropriate evacuation. Naturally, the helium is mixed with the unfused deuterium and tritium in the reactor, and such extraction of helium also extracts useful reactor fuel (along with other gases present in the reactor, such as argon, neon, and xenon).

[0003] A cryopump is a vacuum pump whose operation involves the freezing and adsorption of gases on a cold surface at very low temperatures. Existing magnetic confinement reactors typically use cryopumps cooled to around 4 K to capture most, if not all, of the exhaust materials from the reactor (i.e., helium, deuterium, tritium, and other impurities). For current test systems, the reactor is taken offline at the end of a test shot, and the cryopump is then regenerated to recover useful fuel (i.e., recycle tritium and deuterium) for later reuse in the reactor for future experiments. This process often takes several hours. Therefore, typical existing reactors are considered discontinuous, and they cannot be easily adapted for continuous operation.

[0004] It will be appreciated that taking the reactor offline for several hours to recover the fuel is undesirable from a commercial energy production standpoint; instead, essentially continuous operation of the reactor is desirable. One option is to potentially eliminate the need to recapture the fuel by simply adding more tritium (and deuterium) into the reactor to compensate for any lost material. The problem with this approach is that tritium, in particular, is incredibly expensive (currently approximately $30,000 per gram), and such an approach would require large amounts of tritium (hundreds of grams). Because it is a radioactive material, there are also safety and regulatory considerations against storing such large amounts of tritium.

[0005] Therefore, it is highly desirable to develop a system that allows for effective and continuous tritium recycling (and to a lesser extent deuterium recycling) to enable reactor operation in a commercial environment and reduce the amount of tritium required. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is defined by the independent claims. Additional features will be apparent from the dependent claims and the present specification. Any embodiments described but not included in the claims can be construed merely as examples useful for a better understanding of the invention.

[0007] The examples are provided with a view to addressing at least some of the difficulties facing current magnetic confinement fusion reactors, whether those difficulties are specifically mentioned above or otherwise recognized from this discussion.

[0008] Broadly, this disclosure relates to providing techniques for separating tokamak (or other reactor) exhaust impurities from the fuel stream for rapid fuel recycling at high vacuum pressures. Typical recycling periods are measured in minutes, rather than many hours or days for other methods. During the DT cryosorption cycle, cryogenic pumps are discussed to selectively capture fuel—deuterium and tritium, D&T (sometimes simply labeled DT herein)—and some impurities, while allowing most of the helium and hydrogen to be continuously pumped. This allows rapid recycling of deuterium and tritium with minimal impurities during tokamak (reactor) operation, minimizes tritium inventory, and advantageously, current technology reduces cryogenic power consumption. Therefore, this disclosure represents an important step toward achieving continuous reactor operation that would enable commercial energy production, overcoming a barrier to commercial operation inherent in existing test systems (i.e., the inability to recycle tritium on a reasonable timescale). [Means for solving the problem]

[0009] Thus, one aspect of the invention provides a cryopump for recovering fuel from the exhaust gas of a fusion reactor. The cryopump includes a chamber configured to receive the exhaust gas, a first panel disposed in the chamber and cooled to a first temperature greater than 20 Kelvin (more preferably in the range of 30 to 80 Kelvin), and a second panel disposed in the chamber and cooled to a second temperature in the range of 10 to 20 Kelvin. In a preferred arrangement, the gas is directed through the chamber, first passing through the first panel and then through the second panel, to allow deposition of impurities on the first panel and DT on the second panel.

[0010] The cryopump comprises a first valve configured to isolate the second panel from the first panel (dividing the chamber in half between the first and second panels, thereby providing the second panel isolated from the reactor exhaust). The second panel can then be regenerated, advantageously to recover the DT separately from the impurities from the first panel (and, for that matter, separately from helium treatment).

[0011] In one example, the cryopump includes second and third valves configured to isolate the chamber from the inlet and outlet of the cryopump, respectively, such that the second valve isolates the second panel from the helium processing path, and the third valve isolates the first panel, ready for regeneration, from the impurity processing system.

[0012] In another aspect of the invention, there is provided a fusion power system comprising a reactor and a cryopump as described above, the reactor having a gas outlet suitably connected to the inlet of the cryopump. In one example, the power system comprises at least two cryopumps, a second cryopump also connected to the gas outlet of the reactor.

[0013] In another aspect of the invention, a method for rapid fuel recovery from a fusion power system is provided.

[0014] For a better understanding of the present disclosure, reference will now be made to the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a schematic diagram of a prior art process for fuel recovery. [Figure 2] FIG. 2 shows a schematic diagram of a process for fuel recovery according to the present technology. [Figure 3] FIG. 3 illustrates an example of a cryopump during adsorption. [Figure 4] FIG. 4 illustrates an example of a cryopump during regeneration. [Figure 5]FIG. 5 illustrates another example of a cryopump. DETAILED DESCRIPTION OF THE INVENTION

[0016] At least some of the following embodiments provide improved tritium (and deuterium) recycling techniques for fusion reactors. Other advantages and improvements may also become apparent from the discussion herein.

[0017] FIG. 1 shows a simplified process schematic of a prior art fuel recovery system. Here, a reactor 10 uses deuterium and tritium as fusion fuels for energy and, among other things, to produce a helium by-product. A vacuum pumping system 12 extracts gas from the reactor 10 via an exhaust port. The pumping system 12 includes a cryopump with adsorption panels cooled to around 4 K (degrees Kelvin)—more specifically, typically in the range of 4.2–4.5 K. This temperature is chosen because it allows the cryopump to adsorb helium, tritium, deuterium, and other impurities from the exhaust gas. While the reactor 10 is offline, the cryopump adsorption panels are regenerated (i.e., heated), allowing an exhaust treatment system 14 to separate the materials adsorbed on the cryopump panels. Thus, the exhaust treatment enables fuel recovery 16 by separating deuterium and tritium from other materials captured via the exhaust port. The recovered fuel is typically stored and then, at some later time, used by a material injection system 18 to return fuel to the reactor 10. The above cycle is repeated the next time the furnace is inerted.

[0018] 2 shows a schematic diagram of an improved technique for deuterium / tritium fuel recovery for continuous reactor operation. While the technique is described with reference to exhaust gases, it will be appreciated that the technique can be applied to any suitable outflow of gases from the reactor 10. Also, the following will refer to deuterium and tritium in combination, since this is the current standard fuel mixture for fusion reactors; however, it will be appreciated that the current technique can be applied to other fuel mixtures containing at least one of deuterium and tritium (and primarily tritium, which is generally the more significant of the two).

[0019] Similar to FIG. 1, exhaust gases may be extracted from the reactor via a suitable vacuum pumping system 12. Here, however, the vacuum system 12 includes an improved cryopump 100 and other vacuum pumps for pumping at different pressures (not included in FIG. 2) up to atmospheric pressure. Generally, the improved cryopump 100 is configured to capture deuterium and tritium from the exhaust gases, separate from other impurities and helium. The captured deuterium and, more importantly, tritium are then directed from the cryopump 100 to the material injection system 18 without the need for any extraneous processing. Therefore, the fuel may be rapidly recovered (box 20) and reinjected into the reactor 10. Here, "rapidly" means on the order of minutes or tens of minutes, as opposed to the long timescales of hours over which fuel is currently recovered. Advantageously, a reactor 10 employing an improved cryopump would require only a small tritium inventory, while still allowing continuous operation of the reactor 10. If the existing test system were used for commercial energy production, the tritium inventory required would then be on the order of several hundred grams to operate in a (near) continuous mode; in contrast, the present technology is estimated to require only a tritium inventory of a few grams (e.g., 3 to 4 grams).

[0020] 3 and 4 show schematic diagrams of an example cryopump 100. The cryopump 100 includes a chamber 102 into which exhaust gases are received from the furnace 10, with a first panel 104 and a second panel 106 both disposed (i.e., arranged) in the chamber 102. As described, preferably, the first panel 104 and the second panel 106 are each part of an array of panels aligned together within the chamber 102 (i.e., at a similar point on the axis of the cryopump 100, where the "X" axis is defined as being substantially parallel to the gas inflow into the cryopump 100). That is, the cryopump 100 may include a first array of panels 104' and a second array of panels 106', with the first array of panels 104' including the first panel 104 and the second array of panels 106' including the second panel 106. One or more first panels 104 and one or more second panels 106 are spaced apart in the chamber 102 .

[0021] One or more first panels 104 are cooled to a first temperature, while one or more second panels 106 are cooled to a second temperature. The first and second temperatures are different to provide for adsorption of different substances onto the one or more first / second panels 104, 106; therefore, the example cryopump 100 may be considered a multi-stage cryopump (specifically, a two-stage pump). One or more first panels 104 are configured to capture impurities from the exhaust gas, while one or more second panels 106 are configured to capture unused fuel (i.e., DT) from the exhaust gas. To promote adsorption of substances, some (or all) of the panels 104, 106 may be coated with activated carbon. Other coatings that promote adsorption may alternatively be applied. It will be appreciated that where an array of panels is used, cooling the array to a first or second temperature means setting a target temperature for the array while allowing for some variation (within the target range) of the array.

[0022] The first panel(s) 104 are cooled to a temperature in excess of 20 K (degrees Kelvin). Such a temperature allows for the capture of unwanted impurities from the exhaust gas, but importantly, does not generally capture deuterium and tritium. Preferably, the first panel(s) 104 are cooled to a temperature in excess of 30 K and in excess of 80 K.

[0023] The second panel(s) 106 are cooled to a temperature between 10 K and 20 K, and more broadly, the second panel(s) 106 are cooled to a lower temperature than the first panel(s) 104. Cooling the second panel(s) 106 to between 10 K and 20 K allows for the adsorption of fuel (i.e., deuterium and tritium) onto the second panel(s).

[0024] It will be appreciated that the operating temperatures of all of the above panels are well above the 4K typical of current systems operating cryopumps, allowing for significantly greater energy gains in terms of efficiency compared to such systems.

[0025] Gases enter the cryopump 100 and chamber 102 via an inlet 108. In the furnace system, the inlet 108 is therefore suitably connected (e.g., by components of the vacuum system 12) to the furnace exhaust. The gases pass through the chamber 102 to an outlet 110. As the gases flow through the chamber 102, they first pass through the first panel(s) 104 and then through the second panel(s) 106. This arrangement reduces the amount of impurities deposited on the second panel(s) 106, thereby reducing the need for subsequent deuterium / tritium purification from the second panel(s) 106, although, of course, in principle, the panels could be arranged inside out in the chamber 102. Suitably, during cryosorption of fuel and impurities from the exhaust gas, the adsorption panels could be coupled in parallel.

[0026] The example cryopump 100 is not configured to capture helium or molecular hydrogen. Doing so would require a cryopump panel (or array of panels) set to substantially 4 K. In principle, such a panel / array of panels could be placed in the chamber 102 to provide an additional stage of adsorption. Such an arrangement is not preferred, however, due to the increased energy demands of cooling the set of panels to capture helium and / or hydrogen. Instead, the helium and / or hydrogen are pumped out of the cryopump via the outlet 110. In other words, the inlet 108 and the outlet 110 are in fluid communication through the chamber 102; thus, gas may pass through either of the panels 104, 106 and flow through the cryopump 100. The helium, molecular hydrogen, and other impurities (e.g., other gases) are pumped to the plasma exhaust treatment system 22 (FIG. 2).

[0027] In one preferred example, the cryopump 100 includes a first valve 112 configured to isolate one or more second panels 106 from one or more first panels 104. That is, the first valve 112 has an open position (FIG. 3) in which gas flows freely through the chamber 102, passing through the first and second panels 104, 106 from the inlet 108 to the outlet 110, and a closed position (FIG. 4) in which gas is prevented from flowing through the chamber 102, passing through the one or more second panels 106, and out of the cryopump 100.

[0028] When the second panel(s) 106 are properly isolated from the gas outlet (i.e., while the first valve 112 is closed), the second panel(s) 106 may be regenerated to release trapped fuel (deuterium and tritium). Regeneration of the second panel(s) 106 includes inert cooling of the second panel(s) to a target temperature and may also include active heating of the panel(s) 106 to quickly heat the panel and accelerate the regeneration process.

[0029] In one example, the regenerated fuel may then be immediately routed to the material injection system 18 and recycled to the reactor 10 via a path that includes the outlet 110—which is then at least partially shared by the vacuum flow path through which the helium was previously routed and extracted—but without passing through the plasma exhaust treatment system 22. That is, when the first valve 112 is closed, the general plasma process 22 may be isolated from the cryopump 100, and the appropriate gas flow path to the material injection system 18 may be open. Due to the simplicity of the design of the example cryopump 100, such an arrangement is preferred.

[0030] Therefore, by eliminating the need for additional material processing to separate the fuel from helium and other impurities, a reactor system equipped with the example cryopump 100 may be made more efficient and reduce the need for large tritium inventories by quickly pumping tritium back into the reactor 10.

[0031] Also, one or more first panels 104 may be regenerated while valve 112 is closed. That is, the cooling of one or more first panels 104 may be deactivated—and, optionally, first panel (2) 104 may be actively heated—while one or more second panels 106 are being regenerated on the other side of closed valve 112. In other words, panel regeneration may be accomplished in parallel—as opposed to serial cryosorption—which allows for more efficient operation of the cryopump and associated systems.

[0032] In particular, impurities regenerated from the first panel(s) 104 may be suitably routed (e.g., by appropriate valve / outlet 122, FIG. 4 ) from the cryopump to the plasma processing system 22, isolated from any path taken by that fuel. Alternatively, by raising the temperature of the second panel(s) 106 above 80 K during regeneration, the first valve 112 may be opened (after a predetermined time interval or after measuring a desired amount of fuel recovery from the second panel(s) 106), and the impurities released from the first panel(s) 104 may be released from the cryopump 100 (and the burden of directing the impurities to associated locations located downstream of the cryopump) via the outlet 110.

[0033] It will be appreciated that after regeneration of one or more of the first and second panels 104, 106, the panels may be recooled to an appropriate target temperature, the first valve 112 reopened, and the fuel recovery process resumed.

[0034] It will also be appreciated that in other examples, the cryopump 100 may include a second valve 114 configured to isolate one or more second panels 106 (and, more generally, the chamber 102) from the outlet 110, where the second valve 114 may suitably be configured as part of the outlet 110. In other words, the second valve 114 isolates the chamber 102 from the helium gas outflow system 22.

[0035] More specifically, the second valve 114 has an open position ( FIG. 3 ), which allows gas to flow through the chamber 102 from the inlet 108 to the outlet 110 through the first and second panels 104, 106, and a closed position ( FIG. 4 ), which encloses the second panel(s) 104 from the outlet 110. The combination of the first valve 112 and the second valve 114 therefore creates a sub-chamber 116 within the chamber 102 that is isolated from the rest of the cryopump 100. In other words, the second panel(s) 106 are isolated from the chamber 102.

[0036] In this arrangement, the sub-chamber 116 comprising the one(s) of the second panels 106 may be suitably connected to a dedicated fuel recovery path via a second outlet 118 that is suitably opened (e.g., by an appropriate valve) when the first and second valves 112, 114 are closed and the one(s) of the second panels are restored (FIG. 4), but is otherwise suitably closed when the cryopump 100 is being used to recover fuel.

[0037] It will be appreciated that the cryopump 100 may also include a third valve 120 configured to isolate the first panel(s) 104 (and more generally the chamber 102) from the inlet 108, and that the third valve 120 may also be suitably configured as part of the inlet 108. In other words, the third valve 120 isolates the chamber 102 (and more generally the entire cryopump) from the furnace 10.

[0038] More specifically, the third valve 120 has an open position (FIG. 3) that allows gas to flow through the chamber 102 from the inlet 108 to the outlet 110, past the first and second panels 104, 106, and a closed position (FIG. 4) that seals the cryopump 100 from receiving further exhaust gases. The combination of the first valve 112 and the third valve 120 therefore creates a sub-chamber 122 within the chamber 102 that is isolated from the rest of the cryopump 100. In other words, one or more of the first panels 104 are isolated from further gas flow.

[0039] The subchamber 122 comprising the one(s) of the first panels 104 may be suitably connected to a dedicated impurity handling system, for example, via a third outlet 124 that is suitably opened (e.g., by an appropriate valve) when the first valve 112 is closed (and optionally also the second valve 114 and / or the third valve 120, if such valves are present), but is otherwise closed during cryosorption. In this manner, the one(s) of the first panels 104 may be regenerated to release previously trapped impurities from the cryopump 100 while the reactor 10 is in operation and while fuel is also being regenerated via the separation system.

[0040] In another example, one or more first panels 104 may be regenerated via a gradual deactivation of the cryopump with the first valve 112 closed (when saturated), then one or more second panels 106 are regenerated to recover fuel, the first valve 112 is opened, and then the one or more first panels 104 are regenerated to extract impurities via a suitable system connected to the outlet 110.

[0041] To aid in the continuous operation of the fusion reactor 10, each of the valves 112, 114, and (if present) 120 may be suitably controlled by a timer so that they are activated at predetermined intervals. For example, the first valve 112 may be configured to remain open for at least 2-3 hours of reactor operation before allowing the opening and repeating process, and then automatically controlled to close for 20 minutes to allow for fuel regeneration. Alternatively, diagnostic devices may be positioned to monitor the saturation levels of the first and second panels 104, 106, and panel regeneration (initiated by closing the associated valve) may be initiated based on the determined saturation levels.

[0042] It may also be desirable to provide at least one additional cryopump as part of the vacuum system 12. That is, a second cryopump configured in accordance with the above description may be connected to the gas exhaust from the reactor 10. Thus, when the first cryopump is isolated from the gas exhaust for regeneration of fuel (and / or impurities, if desired), the second cryopump may be used to continue to process the exhaust gases.

[0043] More specifically, when one or more second panels 106 from the first cryopump 100 are isolated from the gas outlet (i.e., isolated from the furnace)—the one or more second panels 106 may be regenerated to recover fuel—the furnace exhaust gas may be directed to a second cryopump 100 comprising one or more third panels (arrays) 104 and one or more fourth panels (arrays) 106, where the one or more third panels are configured to capture impurities and the one or more fourth panels are configured to capture fuel.

[0044] Thereafter, fuel may be reclaimed from the second cryopump in a manner similar to that described above while the first cryopump is reactivated to capture fuel.

[0045] FIG. 5 shows another example cryopump 100′ built on previous technology. Here, the example cryopump 100′ is provided with an additional panel / set of panels, with the goal of increasing the purity of deuterium and tritium absorbed in the second panel(s) 106 to increase the capture of impurities and other reactor gases that do not contain helium / hydrogen, such as xenon, argon, and neon. In such an example, each panel (set) provided in the cryopump 100 represents an additional stage of absorption. In particular, each panel (set) may be suitably set to a different temperature range, and preferably, the temperature of each panel (set) decreases from the first panel(s) 104 to the second (final) panel(s) 106 in the cryopump, i.e., the panels in the cryopump have a decreasing temperature gradient. The more panels provided, the more distinct the separation of deuterium and tritium from other impurities, i.e., the more adsorption stages provided, the higher the purity of deuterium and tritium on the second panel(s) 106.

[0046] More specifically, the example cryopump 100′ comprises a plurality of first panels 105 or an array / set of a plurality of first panels, where three (three sets) of panels 105a, b, and c are spaced apart from one another within the chamber 102 (i.e., separated along an axis of the cryopump 100′, here the X-axis). Each of the plurality of first panels 105 is cooled to a temperature greater than 20 K, preferably between 30 K and 80 K. Each panel (array) is cooled to a different temperature, and preferably the temperature of each of the plurality of first panels 105 decreases the further the panel (array) 105a, b, c is from the inlet 108 and the closer it is to the second panel 106. For example, a first panel (array) 105a of the plurality may be set to a temperature range of 70K to 80K, a second panel (array) 105b may be set to a temperature range of 50K to 60K, and a third panel (array) 105c may be set to a temperature range of 30K to 40K. It will be appreciated that in general, any number of panels may be provided in the plurality of first panels 105, with each provided panel (array) being set to a different temperature. Furthermore, as shown, the plurality of first panels 105 are positioned in the chamber 102 before the first valve 112, allowing the plurality of first panels 105 to be suitably isolated from one or more second panels 106.

[0047] It should also be appreciated that in this example, the operation of the second panel(s) 106 and the remainder of the cryopump 100 ′ is substantially the same as that already described above in connection with the example cryopump 100 .

[0048] In summary, exemplary embodiments of a multi-stage cryopump that facilitates fuel recovery from the exhaust of a fusion reactor have been described. The exemplary embodiments described provide improved technology that facilitates continuous reactor operation, an important consideration for commercial energy production. Additionally, the exemplary embodiments reduce the energy demand for fuel recycling compared to typical technologies.

[0049] Example cryopumps and associated systems can be manufactured industrially. The industrial applications of example embodiments will become apparent from the discussion herein. Additionally, the described exemplary embodiments are affordable to manufacture and simple to use.

[0050] While preferred embodiments of the present invention have been shown and described, it will be recognized by those skilled in the art that modifications may be made without departing from the scope of the invention as defined in the claims.

[0051] Attention is drawn to all papers and documents related to this application that are filed contemporaneously with or prior to this specification and that are open to public inspection herewith, and the contents of all such papers and documents are incorporated herein by reference.

[0052] All features disclosed in this specification, and / or all steps of any method or process so disclosed, may be combined in any combination, except where combinations where at least some of such features and / or steps are mutually exclusive.

[0053] Each feature disclosed in this specification, unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is an example, but not limited to, of a generic series of equivalent or similar features.

[0054] The invention is not limited to the details of the foregoing embodiments, but extends to any novel feature or any novel combination of features disclosed in this specification, or to any novel step or any novel combination of any method or process steps so disclosed. [Explanation of symbols]

[0055] 10 furnace 12 Vacuum Pump System 14 Emissions Treatment System 16 Fuel Recovery 18 Material Injection System 20 boxes 22 Plasma Emission Treatment System 100 Cryopump 102 Chamber 104 Panel 1 105 Panel 1 105a 1st panel (arrangement) 105b 2nd panel (array) 105c 3rd panel (arrangement) 106 Second Panel 108 Entrance 110 Exit 112 First Valve 114 Second Valve 116 Sub-chamber 118 2nd exit 120 Third valve 122 Sub-chamber 124 Exit 3

Claims

1. A cryopump for recovering fuel from exhaust gas of a nuclear fusion reactor, a chamber configured to receive the gas; a first panel disposed within the chamber and cooled to a first temperature, the first temperature being greater than 20 Kelvin; and a second panel disposed within the chamber and cooled to a second temperature, the second temperature being in the range of 10 to 20 degrees Kelvin; and a first valve configured to isolate the second panel from the first panel; A cryopump equipped with:

2. 2. The cryopump of claim 1, wherein the first temperature is in the range of 30 to 80 Kelvin.

3. 3. The cryopump of claim 1, wherein the cryopump is configured to direct gas through the chamber first through the first panel and then through the second panel.

4. 4. The cryopump of claim 1, wherein the first panel is one panel of an array of panels cooled to the first temperature.

5. 5. The cryopump of claim 1, wherein the second panel is one panel of an array of panels cooled to the second temperature.

6. A cryopump according to any one of claims 1 to 5, wherein the first and second panels, and optionally the first and second arrays of panels, are coated with activated carbon.

7. 7. The cryopump of claim 1, further comprising at least one additional panel or array of panels spaced apart from the first panel and cooled to a temperature in excess of 20 Kelvin that is different from the first temperature.

8. 8. The cryopump of claim 7, wherein the first panel and at least one additional panel are arranged to provide a decreasing temperature gradient toward the second panel.

9. 9. The cryopump of claim 1, further comprising a second valve configured to isolate the chamber from an outlet from the cryopump, the second panel being positioned within the chamber between the first valve and the second valve.

10. 10. The cryopump of claim 9, further comprising a third valve configured to isolate the chamber from an inlet to the cryopump, the first panel being positioned within the chamber between the first valve and the third valve.

11. 11. A cryopump according to any one of claims 1 to 10, wherein the first valve, and, when present, the second and third valves, are configured to operate at predetermined intervals.

12. 1. A nuclear fusion power system comprising a reactor having a gas outlet connected to a cryopump, The cryopump comprises: an inlet connected to the gas outlet for receiving gas from the fusion reactor; an outlet in fluid communication with the inlet via a chamber, the outlet providing an outlet for the gas from the cryopump; a first panel disposed in the chamber and cooled to a first temperature, the first temperature being greater than 20 Kelvin; and a second panel disposed in the chamber and cooled to a second temperature, the second temperature being in the range of 10 Kelvin to 20 Kelvin; and a first valve configured to isolate the second panel from the first panel.

13. 13. The fusion power system of claim 12, wherein the cryopump is a first cryopump of at least two cryopumps disposed in the system, and an inlet of a second cryopump of the at least two cryopumps is connected to the gas exhaust of the reactor.

14. A fusion power system according to claim 12 or 13, wherein the first cryopump and, when present, the second cryopump are configured to include any of the optional features of any one of claims 2 to 11.

15. 1. A method for rapid fuel recovery from a nuclear fusion reactor, comprising: the fuel comprises at least one of deuterium and tritium; The method comprises: directing the exhaust gas from the furnace through a first cryopump panel cooled to a first temperature above 20 Kelvin to absorb impurities from the exhaust gas onto the first panel; subsequently directing the exhaust gas through a second cryopump panel cooled to a second temperature of between 10 and 20 Kelvin to absorb the at least one of deuterium and tritium onto the second panel; isolating the second panel from the exhaust gas of the furnace with a first valve and regenerating the second panel to recover the at least one of deuterium and tritium.

16. 16. The method of claim 15, wherein regenerating the second panel to recover the at least one of deuterium and tritium further comprises pumping the recovered at least one of deuterium and tritium back into the fusion reactor.

17. When the second panel is isolated from the exhaust gas, the method further comprises: directing exhaust gas from the furnace through a third cryopump panel cooled to a first temperature above 20 Kelvin to deposit impurities from the exhaust gas on the third panel; 17. The method of claim 15 or 16, further comprising subsequently directing the exhaust gas through a fourth cryopump panel cooled to a second temperature of between 10 and 20 Kelvin to deposit the at least one of deuterium and tritium on the fourth panel.

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