Heat exchanger configuration for nuclear reactors

Abstract

The reactor includes a heat exchanger that transfers thermal energy from the primary reactor coolant to the secondary coolant. The heat exchanger is a small plate-type heat exchanger, and one or more heat exchangers may be arranged around the reactor vessel. Multiple heat exchangers may be spaced vertically, radially, and / or circumferentially around the reactor vessel. The first heat exchanger may be fluidly connected to the second heat exchanger. Two or more heat exchangers may share a heat load and thus may share thermal stress. The heat exchanger may have a third fluid flow path and a third fluid. The third fluid may be used to remove fission products, for leak detection, to create an oxide layer to inhibit the movement of activation products, and / or to provide additional heat transfer.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims the benefit of 35 USC § 119(e) of U.S. Provisional Patent Application No. 63 / 066,788, filed August 17, 2020, titled “Construction of a heat exchanger for a nuclear reactor,” the contents of which are incorporated herein by reference in their entirety. Background Technology

[0003] A heat exchanger is a device that transfers thermal energy from the reactor core of an operating reactor to a secondary fluid, enabling the thermal energy to be used for useful purposes. In some cases, the thermal energy is used to generate steam for power generation, for example, through a steam turbine.

[0004] In many cases, heat exchangers are quite large and occupy a significant amount of space within the reactor vessel. In many instances, heat exchangers are a primary design element of the reactor and largely determine the overall height of the reactor vessel, which in turn affects the overall dimensions of the containment structure and other components.

[0005] Furthermore, large heat exchangers may essentially require part of the flow path near the reactor core, which is subject to relatively high neutron activity. Shielding the heat exchanger and its flow path increases cost, complexity, and the number of components required for installation within the reactor vessel.

[0006] The problem is exacerbated by the fluid circulating within the heat exchanger. For example, in a sodium-cooled fast reactor, the primary coolant is sodium, and the secondary fluid receiving thermal energy from the primary coolant may also be sodium. When sodium is selected as the secondary coolant, many design decisions regarding the heat exchanger are made due to its thermal conductivity. In reactors using a secondary coolant with low thermal conductivity, the heat exchanger may need to be larger. For instance, in a reactor using sodium as the primary coolant and molten salt as the secondary coolant, the heat exchanger must necessarily be much larger than a sodium / sodium heat exchanger. This is because molten salt has a thermal conductivity approximately 100 times lower than that of sodium. Consequently, in some cases, a sodium / salt heat exchanger is more than twice the height of a sodium / sodium heat exchanger to provide similar thermal energy transfer.

[0007] Historically, the coolants available for use in major heat exchangers may be limited by the required heat exchanger size. Furthermore, the size of a typical heat exchanger determines, at least in part, the height of the reactor vessel. Having greater flexibility in selecting primary and secondary coolants, as well as the option to place one or more heat exchangers within the reactor vessel while reducing the overall size of the reactor vessel in the process, would be a significant advantage in the industry. These and other advantages will become apparent with reference to the following description and the attached drawings. means of solving the problem

[0008] According to some embodiments, a plate-type heat exchanger for a nuclear reactor comprises: a plurality of plates; a first fluid inlet, a first fluid outlet, and a first fluid path formed as a guide channel in the plurality of plates that fluidly communicates between the first fluid inlet and the first fluid outlet; and a second fluid path formed as a second guide channel in the plurality of plates and not fluidly communicating with the first fluid path, wherein the second fluid inlet, a second fluid outlet, and a second fluid path that fluidly communicates between the second fluid inlet and the second fluid outlet.

[0009] In some examples, the plate-type heat exchanger further comprises a third fluid inlet, a third fluid outlet, and a third fluid path, wherein the third fluid path is fluidly connected between the third fluid inlet and the third fluid outlet and is not fluidly connected to the first fluid path and the second fluid path. The third fluid path may be configured for purposes other than thermal energy transfer.

[0010] For example, the third fluid path may be configured to accommodate a third fluid different from the first and second fluids, and may be used for leak detection of the first fluid, the second fluid, or both. Optionally, the third fluid may be used to create an oxide layer within the third fluid path. In some cases, the third fluid may be used to capture fission products or activation products, such as tritium, for example.

[0011] According to some examples, the first fluid inlet and the first fluid outlet are formed on the same side of the plate-type heat exchanger. In some cases, a coaxial conduit is connected to the first fluid inlet and the first fluid outlet, and the coaxial conduit defines an inner fluid conduit and an outer fluid conduit, the inner fluid conduit is connected to one of the first fluid inlet and the first fluid outlet in fluid communication, and the outer fluid conduit is connected to the other of the first fluid inlet and the first fluid outlet in fluid communication.

[0012] The third fluid may be hydrogen, helium, CO2, or a combination thereof.

[0013] In some embodiments, the first fluid is in the first fluid path and the second fluid is in the second fluid path. The first fluid and the second fluid may be different fluids, and in some cases, may be the same fluid. The first fluid may be sodium, and in some cases, the second fluid may be molten salt.

[0014] In some cases, the plate-type heat exchanger is a first plate-type heat exchanger, and a second plate-type heat exchanger may be fluidly connected to the first plate-type heat exchanger. For example, an array of heat exchangers may be provided in which two or more heat exchangers are fluidly connected together, such as two, three, four, six, eight, or more heat exchangers.

[0015] In some cases, the first fluid outlet of the first plate-type heat exchanger is in fluid communication with the first fluid inlet of the second plate-type heat exchanger. Multiple heat exchangers may be configured to cooperate to handle the heat load of a reactor.

[0016] In some examples, at least some of the plurality of heat exchangers are fluidly connected by a fluid header. That is, the fluid header can transfer fluid from a common source to some of the plurality of heat exchangers.

[0017] In some cases, at least some of the plurality of heat exchangers are piped in series. In some cases, at least some of the plurality of heat exchangers are piped in parallel. For example, some of the heat exchangers may be piped in series, and other heat exchangers may be piped in parallel. In some cases, a first group of heat exchangers may be piped in series, while another group of heat exchangers may be piped in parallel, and in some cases, the two groups are piped to be fluidly connected to each other.

[0018] According to some embodiments, a method for removing fission products or activation products from a reactor coolant in a heat exchanger of a reactor comprises: positioning a plate-type heat exchanger in a reactor vessel; passing a primary coolant through a first fluid path of the plate-type heat exchanger; passing a second coolant through a second fluid path of the plate-type heat exchanger; passing a third fluid through a third fluid path of the plate-type heat exchanger, wherein the third fluid is selected to attract the fission products or activation products; and removing the fission products or activation products together with the third fluid from the plate-type heat exchanger. Brief explanation of the drawing

[0019] A detailed description is provided with reference to the attached drawings. In the drawings, the leftmost digit(s) of a reference number identify the drawing in which the reference number first appears. The same reference number used in other drawings indicates similar or identical components or features. FIG. 1a is a schematic diagram of a plate-type heat exchanger according to some embodiment for transferring thermal energy from a high-temperature fluid to a low-temperature fluid; FIG. 1b is a schematic diagram of a plate-type heat exchanger according to some embodiment having coaxial inlets and outlets; FIG. 2a illustrates a schematic diagram of a sodium-cooled fast reactor according to some embodiment having a shell and a tubular heat exchanger; FIG. 2b illustrates a schematic diagram of a sodium-cooled fast reactor according to some embodiment having a plate-type heat exchanger; FIG. 3a illustrates a drawing of a plate-type heat exchanger according to some embodiment having an inline configuration; FIG. 3b illustrates a cross-sectional view of a plate-type heat exchanger of FIG. 3a according to some embodiments; FIG. 4b illustrates a drawing of a plate-type heat exchanger having a side configuration according to some embodiments; FIG. 4b illustrates a cross-sectional view of a plate-type heat exchanger of FIG. 4a according to some embodiments; FIG. 5 illustrates an arrangement of heat exchanger cores according to some embodiments coupled to a header; FIG. 6 illustrates an arrangement of heat exchanger cores according to some embodiments coupled to a header by piping; FIG. 7 illustrates a plurality of heat exchanger cores according to some embodiments arranged in an arc shape; FIG. 8 illustrates a plurality of heat exchanger cores according to some embodiments arranged in a stacked array; FIG. 9 illustrates a plurality of heat exchanger cores according to some embodiments arranged circumferentially around a portion of a reactor vessel; FIG. 10 illustrates a plurality of heat exchanger cores according to some embodiment, arranged in a plurality of rows and columns and configured to extend along the inner wall of a reactor vessel; FIG. 11 illustrates a plurality of heat exchanger cores according to some embodiment, arranged at a predetermined angle with respect to the vertical and arranged to be in fluid communication with the header by means of piping; FIG. 12 illustrates exemplary locations of the arrangement of heat exchanger cores within a reactor vessel according to some embodiments. Specific details for implementing the invention

[0020] The present disclosure generally relates to a heat exchanger apparatus for a nuclear reactor. Additionally, the present disclosure relates to the arrangement and location of multiple heat exchangers throughout the reactor vessel. In some cases, the heat exchangers allow flexibility in the arrangement, orientation, and number of heat exchangers used. Additionally, a wide range of secondary coolants may be used in the described heat exchangers, and in some cases, a third fluid path may be provided through one or more heat exchangers.

[0021] In some embodiments, a small heat exchanger is provided within the reactor vessel of a reactor to transfer heat from the primary coolant to the secondary coolant within the reactor core. In some cases, the heat exchanger transfers thermal energy from sodium to salt. For example, in a sodium-cooled fast reactor ("SFR"), sodium may be used as the primary coolant within the reactor vessel. As sodium circulates throughout the reactor vessel via natural circulation, one or more circulation pumps, or a combination of circulation methods, sodium closer to the highly reactive region receives thermal energy and is heated. The heated sodium may flow through a heat exchanger, where thermal energy is transferred from the primary sodium coolant to the secondary coolant, which in some cases is sodium, salt, or some other secondary coolant.

[0022] Plate heat exchangers can be used to transfer thermal energy from a primary coolant (e.g., sodium) to a secondary coolant (which may be molten salt in some cases). In some cases, a plate heat exchanger may have two inlets and two outlets. For example, a plate heat exchanger may have an inlet and an outlet for sodium, and an inlet and an outlet for salt. These liquid flow paths can be defined by channels within each plate of the heat exchanger, and the plates keep the liquids separated and maintain thermal communication as the plates conduct thermal energy from the high-temperature fluid to the low-temperature fluid.

[0023] In some cases, a third inlet and outlet may be provided, and a third fluid flow path is defined by one or more plates of the heat exchanger. For example, a third fluid may be provided for any purpose, such as additional heat transfer to detect leaks of high-temperature or low-temperature fluids in the heat exchanger, removal of fission products or activation products (e.g., tritium), or some other purpose. In some cases, hydrogen may be used as the third fluid in the heat exchanger. In some cases, CO2 may be used as the third fluid in the heat exchanger. In some cases, helium may be used as the third fluid in the heat exchanger.

[0024] In any case, the third fluid may be used for leak detection. For example, one or more detectors may be placed in the third fluid stream downstream of the heat exchanger, and the third fluid may be tested for the presence of one or more substances that were not present in the third fluid before it entered the heat exchanger. For example, the third fluid may be tested for salt after passing through the heat exchanger, and the presence of salt in the third fluid (in liquid or vapor form) indicates a salt leak within the heat exchanger.

[0025] A third fluid within the heat exchanger may be used additionally or alternatively to attract fission and activation products. For example, a third fluid (e.g., helium, hydrogen, etc.) may be used as a third fluid to reduce tritium. The third fluid may be selected and / or configured such that fission products or activation products have a higher affinity for the third fluid than for the coolant salt. In this way, the coolant fluid, such as the salt, acquires a reduced amount of tritium compared to when there is no third fluid in the heat exchanger.

[0026] In some cases, a third fluid in a heat exchanger can be used to form an oxide layer within the heat exchanger. As discussed below, oxide layers have been shown to reduce tritium penetration. In sodium / salt heat exchangers, for example, the sodium flow path is unlikely to have a significant oxide layer within the flow path, while the salt flow path can form a measurable oxide layer to reduce tritium penetration to some extent. By introducing a third fluid configured to generate an oxide layer, tritium penetration can be dramatically affected and reduced compared to the case without an oxide layer.

[0027] For example, a third fluid, such as CO2, may pass through a heat exchanger via a third fluid path to intentionally form an oxide layer on the surface within the heat exchanger. The third fluid may be additionally used for other purposes, such as leak detection, as described herein. In some cases, a third fluid, such as CO2, may pass through the third fluid path, and then a fourth fluid may pass through the third fluid path. For example, after CO2 flows through the third fluid path, helium may flow through the third fluid path at another time. In this way, the third fluid path may be used for various purposes, such as, for example, without limitation, the formation of an oxide layer, the capture of fission products or activation products, the provision of additional heat transfer used for leak detection, or some other purpose. One of these activation products that may be captured within the heat exchanger is tritium.

[0028] Tritium is generated in all nuclear reactors by nuclear reactions in the core (fuel and other core components) and in the moderator / coolant. Tritium atoms are highly mobile and can diffuse through cladding and other metal barriers, and can be released into the environment unless "trapped" and disposed of as regulated radioactive waste. While tritium production in LWRs (Light Water Reactors) and SFRs is similar, the release fraction (released tritium / generated tritium) clearly differs between the two reactor types. Much more tritium is released into the environment from LWRs than from SFRs.

[0029] In some cases, sodium system cold traps are used to control tritium release into the environment. Cold traps can operate at low inlet temperatures (e.g., about 115 °C) for cold trap efficiencies that can be about 70% in some cases. Regardless of the presence or absence of a steam generator, sodium-cooled fast reactors generally rely on sufficient (n,p) reaction in the primary sodium to maintain high trap efficiencies in the primary and secondary cold traps and keep tritium release into the environment below specified levels. 1 H can be generated.

[0030] Oxidation of the metal surfaces of sodium system piping and components can reduce the rate of tritium diffusion through the metal barrier by up to about 88 times. In some cases, metal surfaces in contact with liquid sodium will form an oxide coating, as sodium removes oxygen, so there is almost no oxide coating, and generally only the surfaces exposed to air will form an oxide coating.

[0031] For SFRs using mixed oxide fuel (MOX) or ternary alloy metal fuel, the production of tritium by ternary fission is approximately 16.9 mCi / MWD. In some cases where TWRs use binary alloy metal fuel, the ternary fission production rate of tritium is approximately 13.6 mCi / MWD because the tritium yield of U-235 is 76% of the yield value of Pu-239.

[0032] Tritium is highly mobile and diffuses through most metal barriers. Therefore, in many cases, some tritium will be released from the reactor core into the general environment during normal power plant operation. Tritium is also a radioisotope of concern when evaluating accident-related radiation source items. Tritium is generated in the reactor core by the ternary fission of fuel and the neutron capture of boron (B) in control rods and radiative shielding.

[0033] Tritium atoms generated from fuel or B4C absorbents generally react chemically with sodium through fin cladding to form Na 3 It diffuses into primary sodium to form H (sodium trioxide). In many cases, Na 3 Most of the H can be captured in the primary cold trap before it can diffuse through the walls of the primary sodium loop into one of the inert cells. Some tritium reacts with sodium through the piping of the I heat exchanger (intermediate heat exchanger) to form Na 3 There may be a tendency to diffuse into one of the three auxiliary loops capable of forming H, and Na 3 H can be captured in a secondary cold trap.

[0034] Tritium not captured in the "secondary cold trap" can diffuse through the walls of the secondary sodium loop piping to the piping outside the containment structure and can be discharged into the external environment along with tritium diffusing through the "tube walls" of the dump heat exchanger (D heat exchanger).

[0035] Since tritium is a small atom, it is expected to diffuse through most metal barriers. However, if an oxide coating is present on the metal surface, the diffusion rate of tritium is significantly reduced by approximately 88 times. This effect is relative to the environment 3 It significantly suppresses the emission rate of H.

[0036] In some embodiments, tritium release into the environment can be controlled by the performance of the sodium system cold trap. In the case of a sodium-cooled LMR, impurities in the sodium coolant are maintained below a specified concentration to protect the integrity of the cladding. The impurity concentration is monitored by a Plugging Temperature Indicator (PTI), a device that measures the sodium flow pressure drop (ΔP) across the orifice plate. An increase in ΔP indicates that sodium impurities (oxides and hydrides) have begun to precipitate, which is because the concentration of sodium impurities in the sodium coolant has increased above an acceptable range. The sodium treatment system cold trap maintains the impurity level below the concentration required by the technical specifications.

[0037] In some cases, most tritium fission products can be removed using cold traps in the primary sodium treatment system, but some tritium may be transferred to the coolant salt, for example, through a sodium-salt heat exchanger. In some cases, one or more cold traps in the salt loop can be used to remove tritium from the coolant salt loop, thereby reducing the amount of tritium in the salt loop. However, tritium can be removed within the heat exchanger itself, for example, by passing the fluid through a heat exchanger capable of capturing tritium as it passes through the heat exchanger so that the tritium is captured downstream.

[0038] FIGS. 1a and 1b illustrate a small heat exchanger (100) that can be formed as a plate-type heat exchanger in which two or more fluids are separated by any suitable number of plates (102(1), 102(2), 102(n)). The plates may have fluid flow channels formed internally, which may be formed through machining, chemical etching, laser etching, or some other suitable process. The plates may provide thermal communication between two or more fluids, for example, through material conduction. In some cases, the plates may be fused together to form a monolithic structure. As illustrated, a primary reactor coolant (104), which may be sodium, is introduced into the heat exchanger from an upper inlet (106) through which the coolant flows through the channels of the plates and exits the opposite side of the heat exchanger from an outlet (108). A second inlet (110) for a secondary coolant fluid, which may be salt, may be provided at one or more locations of the heat exchanger (100). A secondary coolant fluid outlet (112) allows the secondary coolant to exit the heat exchanger (100). In some cases, the second coolant loop includes a coaxial pipe in which an inner pipe extends through an outer pipe. The inner pipe may be connected to the inlet of the heat exchanger and the outer pipe may be connected to the outlet of the heat exchanger.

[0039] In this configuration, the salt inlet and outlet can be formed on the same side of the heat exchanger.

[0040] In some cases, the outlet (108) of the first heat exchanger (100(1)) provides an input to the second heat exchanger (100(2)). In some cases, two or more heat exchangers may be directly connected so as to be fluidly connected to each other, such that the fluid outlet of the first heat exchanger provides a fluid inlet to the second heat exchanger. This arrangement may allow smaller heat exchangers to be utilized within the reactor vessel while reducing thermal stress applied to the heat exchangers and allowing for greater efficiency.

[0041] For example, if there is a desired temperature difference (ΔT) between the inlet and outlet of a heat exchanger, providing a single heat exchanger to transfer thermal energy results in thermal stress on that heat exchanger. If two or more heat exchangers are used to affect the same ΔT, each heat exchanger can be responsible for a heat transfer smaller than the desired total ΔT. In this way, two or more heat exchangers each experience less thermal stress than a single heat exchanger responsible for the total ΔT.

[0042] In some embodiments, two or more heat exchangers are fluidly connected together but not structurally connected, so that each of the two or more heat exchangers is freely distorted and expanded / contracted independently of each other. That is, the two or more heat exchangers handle thermal stress independently. As a result, a robust heat transfer system is obtained that can manage heat transfer while reducing the total thermal stress on the heat exchangers by distributing the thermal stress among the multiple heat exchangers. Although flow resistance and pressure drop may increase, these losses can be mitigated by the design of the heat exchangers, the through-flow paths, and the increased lifespan of the heat transfer system.

[0043] In addition, the smaller the size of the heat exchanger, the greater the opportunity to place it in appropriate locations within the reactor vessel. For example, by utilizing multiple heat exchangers, they can be spaced radially, vertically, cylindrically, or in a combination thereof throughout the reactor vessel.

[0044] Suitable heat exchangers (100) include, without limitation, printed circuit heat exchangers, plate heat exchangers, molded plate heat exchangers, or hybrid heat exchangers in which two or more media flow from both sides of one or more combined plates. The cooling media may be in a high-pressure state, but in some embodiments, they are in a low-pressure state. In some embodiments, the working fluids, which are sodium and salt, may flow from both sides of one or more combined plates through a 2D or 3D plate pattern. The 2D or 3D plate pattern may be configured to produce a desired thermal length and pressure drop. As used herein, sodium and salt will be used as exemplary working fluids within the heat exchanger, with sodium used as a cooling fluid within the reactor core and salt used as a heat transfer fluid to transfer thermal energy outside the reactor vessel. In some embodiments, the heat exchanger is used with a sodium pool-type reactor.

[0045] According to some embodiments, a sodium inlet (106) may be formed adjacent to one side of the heat exchanger (100), and a sodium outlet (108) may be formed on the opposite side of the heat exchanger (100). In some embodiments, the sodium inlet (106) may be adjacent to the upper surface of the heat exchanger (100), and the sodium outlet (108) may be adjacent to the bottom surface of the heat exchanger (100) within a configuration installed in a reactor vessel. In some embodiments, the sodium inlet (106) may be higher than the sodium outlet (108). However, in other embodiments, the sodium inlet (106) may be on or adjacent to any side of the heat exchanger (100), and the sodium outlet (108) may be on or adjacent to any other side of the heat exchanger (100). In many cases, the sodium inlet (106) and sodium outlet (108) are on both sides of the heat exchanger (100).

[0046] The salt inlet (110) may be located on one side of the heat exchanger (100) or adjacent thereto, which may be a side orthogonal to the side where the sodium inlet (106) is formed. The salt outlet (112) may be formed on the same side as the salt inlet (110) to accommodate a salt loop pipe that can enter and exit from the same side of the reactor vessel. However, the salt inlet (110) and the salt outlet (112) may be formed on different surfaces of the heat exchanger (100). In some cases, the salt inlet (110) and the salt outlet (112) may be coaxial and may be formed as an inner conduit surrounded by an outer conduit.

[0047] The heat exchanger (100) may be formed of a series of parallel plates (102(1), 102(2), 102(n)) having surface grooves (114) arranged adjacent to each other to form a series of channels when the plates (102) are joined together. The surface grooves (114) may be formed by photochemically etching, mechanically forming, or through some other process on the surface of the plates, and may have a size and arrangement that provide desired flow characteristics such as fluid path length and pressure drop.

[0048] In many cases, the plates (102) are diffusely bonded to each other, which is a solid-state welding process that restores the bond to the strength of the base metal, allows for excellent thermal-hydraulic performance, and allows for the design optimization of 2D and / or 3D fluid paths through the heat exchanger (100).

[0049] A passage (116) for the second fluid may be formed through a plate having a channel for guiding the first fluid. In some embodiments, a coaxial conduit (118) may be used for the inlet and outlet of the second fluid. In some cases, the inlet and outlet of the second fluid may be formed on one side of the heat exchanger (100) for simplification of piping.

[0050] In some embodiments, a header or manifold (not shown) may be attached to a fluid inlet or outlet that provides a fluid communication path through all layers of the heat exchanger (100) simultaneously. Alternatively or additionally, a port may be formed during the plate forming step to provide an integral header to the heat exchanger (100). In some cases, the heat exchanger (100) may be formed with a semi-port consisting of a mixture of headers and ports connected by a manifold.

[0051] The heat exchanger (100) can be formed from any suitable material and can be formed to a size appropriate for the intended use. In many cases, the heat exchanger (100) can be formed substantially smaller than a shell and tubular heat exchanger for the same use. That is, when used in a reactor vessel, a heat exchanger (100) designed as a sodium / salt heat exchanger can be substantially smaller than a shell and tubular heat exchanger configured for sodium / salt heat transfer having a similar thermal energy transfer capability. In some cases, the heat exchanger (100) requires about seven times less volume than a similar shell and tubular heat exchanger for a similar application.

[0052] In the illustrated example, primary sodium flows downward through a channel formed between the plates of the heat exchanger (100) from a sodium inlet (106) formed on the upper surface to a sodium outlet (108) formed on the bottom surface of the heat exchanger (100) through an open slot. Salt is introduced through an inlet (110), distributed through a distributor to a low-temperature channel, flows upward within a channel formed in the heat exchanger (100), and is discharged from a salt outlet (112). This configuration, in which a high-temperature fluid is introduced / extracted near the top of the heat exchanger and a low-temperature fluid is introduced / extracted near the bottom of the heat exchanger, promotes efficient fluid flow by utilizing a natural convection cycle. For example, a temperature difference in the fluid typically causes the higher-temperature fluid to have a lower density than the colder part of the fluid. Consequently, the heated fluid tends to rise, and the colder fluid will descend due to gravity.

[0053] An acceptable pressure drop can be specified, and generally, a lower pressure drop is desirable to reduce operating costs and improve cycle efficiency. In some embodiments, the sodium pressure drop across the heat exchanger (100) is less than about 6 psi, or less than about 5 psi, or less than about 4 psi, or less than about 3 psi. A lower pressure drop generally may require low viscosity and short flow length of the coolant, which directly affect the corresponding heat transfer coefficient. The pressure drop can be adjusted by changing the flow length, fluid viscosity, and / or flow width, and the overall heat transfer can likewise be affected by changing the number of layers and the heat transfer area.

[0054] The plate surface type can be adjusted for a specific purpose and can be formed to improve surface density and heat transfer coefficients, and can be formed with pins having any suitable arrangement such as serrated, herringbone, or perforated. Of course, other arrangements are possible and considered herein. In combination or alternatively, the passages can be formed directly on the plate through any suitable method, but in some cases, they are formed by photochemical etching.

[0055] The passage may have any appropriate size and cross-sectional shape. In some embodiments, the formed channel is semicircular with a radius of about 0.5 mm, or about 0.75 mm, or about 1 mm. Of course, other appropriate cross-sectional shapes and sizes are considered depending on the design flow parameters of the heat exchanger.

[0056] FIGS. 2a and 2b illustrate the relative size difference between the sodium / sodium shell and tubular heat exchanger (200) (Fig. 2a) and the sodium / salt small heat exchanger (100) (Fig. 2b). In particular, the sodium / salt shell and tubular heat exchanger (200) is significantly larger than the sodium / sodium shell and tubular heat exchanger (100) shown in FIG. 2a.

[0057] FIG. 2a illustrates a schematic diagram of a reactor (202) having a shell and tubular heat exchanger (200) designed for sodium / sodium heat transfer. As can be seen, the sodium / sodium heat exchanger (200) is one of the largest components within the reactor vessel (204) and is a major design element in the design of the reactor (202). In fact, the sodium / sodium heat exchanger (200) determines most of the height of the reactor vessel (204), which ultimately affects the overall size of the containment structure and other components.

[0058] Furthermore, shielding the sodium / sodium heat exchanger (200) is difficult and expensive because the sodium / sodium heat exchanger (200) is adjacent to the core (206) which is subject to relatively high neutron activity. Shielding is difficult due to space constraints within the reactor vessel (204) and the size of the heat exchanger (200). When replacing the shell and tubular sodium / sodium heat exchanger (200) with a shell and tubular sodium / salt heat exchanger, the aforementioned considerations are exacerbated because the sodium / salt shell and tubular heat exchanger is significantly larger than the illustrated sodium / sodium shell and tubular heat exchanger (200).

[0059] In many common configurations, the coolant salt has a thermal conductivity about 100 times lower than that of sodium. Consequently, sodium / salt shell and tubular heat exchangers require a much larger heat exchanger than sodium / salt heat exchangers. In some cases, the sodium / salt heat exchanger is more than twice the height of the sodium / salt shell and tubular heat exchanger (200). In some cases, it may be advantageous to use a sodium / salt heat exchanger where the salt is, for example, the working fluid in an integrated energy system and the salt is the thermal energy storage medium. By relying on a sodium / salt heat exchanger, the typical intermediate sodium loop, which receives thermal energy from the primary coolant inside the reactor vessel (204) and transfers it to the salt loop outside the reactor vessel (204), can be eliminated. However, any gain realized from the elimination of the intermediate sodium loop is quickly lost because the reactor vessel (204) must be significantly larger (e.g., by a factor of 2) to enable the sodium / salt shell and tubular heat exchanger. Likewise, the containment structure must also be increased in size to accommodate a larger reactor vessel (204).

[0060] In some embodiments, the heat exchanger within the reactor vessel (204) plays a significant role in the size of the reactor vessel (204). By reducing the size of the heat exchanger, the size of the reactor vessel can be reduced accordingly. In some embodiments, a small heat exchanger (100) as substantially described throughout the embodiments of this specification is used as the primary sodium / salt heat exchanger (100) within the reactor vessel (204).

[0061] As illustrated in FIG. 2b, one or more heat exchangers (100) may be located within the reactor vessel (204) at a distance from the core (206). In some cases, the distance is important in terms of radiation exposure. For example, the further the heat exchanger (100) is from the core (206), the less the heat exchanger (100) is exposed to radiant energy. Consequently, the further the heat exchanger (100) is placed from the core (206), the less shielding is required to reduce salt activation within the salt loop. Additionally, as the distance of the heat exchanger (100) from the core (206) increases, the natural circulation of sodium within the reactor vessel (204) is improved and the size of the circulation pump (208) can be reduced, thereby obtaining additional efficiency and size advantages. In some cases, using one or more heat exchangers (100) within the reactor vessel (204) allows the reactor (202) to output a larger amount of thermal energy or to be reduced in size without sacrificing the amount of thermal energy output.

[0062] Compared to the shell and tube heat exchanger (200) of FIG. 2a, which is adjacent to the core (206) and requires a large amount of shielding to reduce the activation of the heat transfer fluid, the heat exchanger (100) is smaller and located further away from the core (206), thereby reducing the amount of shielding required. Thus, the heat exchanger (100) allows for pool reactor designs by greatly simplifying the design, construction, shielding, piping, and required costs. In some embodiments, the heat exchanger (100) is used in a pool reactor. In some embodiments, the pool reactor is a sodium pool reactor. In some cases, the sodium pool reactor operates in the fast neutron spectrum.

[0063] In some embodiments, the pressure in the salt loop within the heat exchanger (100) is higher than the pressure in the sodium loop within the heat exchanger (100). Consequently, any leak in the heat exchanger (100) will cause the salt to flow into the sodium. Any potential leak in the heat exchanger (100) can be detected in the cover gas system of the reactor (202). The size and location of the heat exchanger (100) facilitate the removal and replacement of the heat exchanger (100), thereby increasing the maintenance and replacement efficiency of the heat exchanger (100) compared to shell and tubular heat exchangers (200).

[0064] In some embodiments, multiple heat exchangers may be utilized in a pool-type reactor. As previously mentioned, the sodium inlet may be located at a higher elevation in the heat exchanger (100), and the sodium outlet may be located at a lower elevation in the heat exchanger (100). The salt inlet and outlet may be located on the same side of the heat exchanger (100) and may be positioned to improve the efficiency of installation, piping, and optional replacement of the heat exchanger (100). In some embodiments, the salt inlet and outlet may be provided by coaxial inlet and outlet pipes. Of course, other configurations are possible, such as separate non-coaxial pipes, as well as other arrangements of the salt inlet and outlet that may be located on adjacent or opposite sides of the heat exchanger (100).

[0065] Sodium outlets from two or more heat exchangers can be merged into a single sodium outlet that returns cooled sodium to the core (206). By utilizing salt as a working fluid to receive thermal energy from the reactor (202) and transfer it to a thermal energy storage system, additional sodium loops are eliminated, thereby improving the need for large sodium pipes with sodium fire protection and shielding, further simplifying construction and associated costs.

[0066] Although an exemplary heat exchanger (100) has been described with a sodium pool type reactor, the features and advantages described herein can be equally applied to other reactor types. Likewise, the described cooling medium uses salt as an example, but this is exemplary and other media and media types are possible.

[0067] FIG. 3a illustrates a sample heat exchanger (300), and FIG. 3b illustrates a cross-section of the heat exchanger (300). The heat exchanger (300) includes a housing (302) and may include one or more mounting surfaces (304), such as a flange, that can be used to mount and / or position the heat exchanger (300). The heat exchanger (300) may include two pairs of inlets / outlets to allow two types of working fluids to pass through the heat exchanger (300) so that one fluid receives thermal energy from the other fluid.

[0068] The heat exchanger (300) can be designed and configured to have inlets and outlets of desired positions and orientations. For example, in some cases, two options for delivering a working fluid, such as salt, to the heat exchanger (300) are an inline or a side interface. For example, an inline interface, as shown in FIGS. 3a and 3b, is an interface in which the inlets and outlets are located on opposite sides of the heat exchanger, whereas a side interface is an interface in which the inlets and outlets are not opposite but rather on orthogonal sides or on the same side.

[0069] In some cases, the inline routing option provides the minimum height / width of the routing option while potentially adding length. The inline option can also direct the interface piping directly to the high and low temperature sodium flows. An alternative is mixed routing, where one fluid path is configured as inline routing and a second fluid path is configured as lateral routing. The fluid path routing can be determined as needed based on the location and orientation within the reactor vessel, along with the necessary connections and piping.

[0070] FIGS. 4a and 4b illustrate a sample heat exchanger (400) having a lateral fluid path provided with an inlet (402) and an outlet (404) on the same side of the heat exchanger (400). In some cases, the core of the heat exchanger (400) is sealed to prevent large leakage from the hot pool to the cold pool within the sodium pool inside the reactor vessel. In some cases, the heat exchanger (400) is designed with a measured leakage between the hot pool and the cold pool, which can simplify the design rather than designing the heat exchanger (400) to prevent all leakage. This may also allow for the omission of baffles typically used to suppress leakage within the heat exchanger (400).

[0071] In some cases, the heat exchanger (400) experiences a temperature difference between the high-temperature pool at the inlet (402) and the low-temperature pool at the outlet (404), which causes thermal stress in the heat exchanger (400). Accordingly, the heat exchanger may be designed to account for relative movement in the axial and vertical directions (the lateral direction is more important) of the heat exchanger (400). In some cases, a sliding labyrinth seal (406) is used to allow thermal expansion and contraction of the heat exchanger in the longitudinal direction while maintaining the fluid flow path. Of course, other suitable structures may be provided to allow thermal expansion and contraction while maintaining the fluid seal.

[0072] In some cases, the sliding labyrinth seal (406) allows the heat exchanger (400) to be inserted into or removed from a fixed space between the piping or adjacent heat exchangers (400). In some cases, the sliding labyrinth seal (406) may allow the entire length of the heat exchanger (400) to be reduced so that it is inserted into a fixed length position, and then extended to be joined to an adjacent structure. Of course, other structures, such as separate sealing plates, may be optionally attached to provide secure attachment as well as fluid sealing for the heat exchanger (400).

[0073] One method of managing thermal stress in the heat exchanger (400) is to provide a heat dissipation sleeve (408) that surrounds at least a portion of the heat exchanger (400) and allow some fluid from the hot pool to leak into the heat dissipation sleeve (408). Diluting some of the hot fluid into the heat dissipation sleeve can reduce periodic thermal stress on the heat exchanger walls.

[0074] FIG. 5 illustrates an arrangement (500) of a heat exchanger core (510) using alternating high and low temperature plenums and headers. In some cases, the high temperature plenum (502) may be in fluid communication with the high temperature header (504). Similarly, the low temperature plenum (506) may be in fluid communication with the low temperature header (508). The low temperature header (508) may provide an inflow salt that receives thermal energy from a primary coolant (e.g., sodium) flowing within the plates of the heat exchanger. The high temperature header (504) may provide a flow path for the high temperature fluid (e.g., salt) to be discharged from the high temperature plenum (502).

[0075] The heat exchanger core (510) may be formed of a plurality of combined plates, each defining a fluid path, as described in various embodiments of this specification. The plates of the heat exchanger core (510) may separate alternating high-temperature plenums (502) and low-temperature plenums (506). As used herein, a group of combined plates may be referred to as the heat exchanger core (510). In the presented example, multiple heat exchanger cores are used together within a shared heat exchanger body. Any suitable number of heat exchanger cores may be used within the heat exchanger body.

[0076] In some embodiments, a plurality of heat exchanger cores are provided to meet the thermal load requirements of the reactor. The number of heat exchanger cores can be selected based on the total thermal load of the reactor, the designed cyclic thermal stress of the heat exchangers, and the ΔT of the inflow and outflow fluids. In some cases, 12, 24, 36, 48, 50 or more heat exchanger cores may be provided to handle the thermal load of the reactor. The heat exchangers may be spaced around the cores in any suitable arrangement and may be fluidly connected to one another. In some examples, some of the plurality of heat exchangers are fluidly connected to others of the plurality of heat exchangers.

[0077] To allow thermal expansion and contraction of the heat exchanger core (510) in response to a heat load, a seal such as a welded bellows or some other expansion seal that allows limited movement of the coupling between adjacent heat exchanger cores or adjacent heat exchangers may be provided.

[0078] FIG. 6 illustrates an arrangement (600) of heat exchanger cores (602(1), 602(2), 602(n)) in which a low-temperature header (604) and a high-temperature header (606) are coupled to an individual heat exchanger core (602) by piping (608) that provides fluid communication between the individual heat exchanger core (608) and the low-temperature header (604) or the high-temperature header (606). The heat exchanger core (602) may be as substantially described herein for the heat exchanger embodiment and may be oriented vertically or horizontally or in some other orientation.

[0079] In some cases, this arrangement allows individual cores (602) to be efficiently installed, removed, and / or replaced, and allows for additional space between individual cores (602) to accommodate thermal expansion and contraction. In some cases, the heat exchanger cores (602) are all connected to a common header (604) in a parallel piping configuration, whereas in other cases, the heat exchanger cores (602) are piped in series such that the outlet of the first heat exchanger core can be connected to the inlet of the second heat exchanger core. Whether piped in series or in parallel, the circuits of the heat exchanger cores may each handle only a portion of the total temperature change of the heat exchanger. In some cases, each heat exchanger core (602) may be designed to handle a specific temperature range within the total heat load of the heat exchanger. For example, the first heat exchanger core may be designed to handle fluid operating temperatures at the thermal limit of the primary coolant in a reactor. That is, the first heat exchanger core may be designed and configured differently from the second heat exchanger core. Individual cores can utilize different materials, flow path lengths, pressure drop, and / or other characteristics of the heat exchanger core.

[0080] FIG. 7 illustrates a stacked configuration (700) for heat exchanger cores (702(1), 702(2), 702(n)). The heat exchanger cores (702) may be substantially as described herein in relation to the heat exchanger embodiments. The cores (702) may be oriented vertically, horizontally, or in some other orientation. In some cases, the cores (702) may be arranged circumferentially and / or radially around the reactor vessel. In some cases, the outer ring of the core (704) is located closer to the wall of the reactor vessel than the inner ring of the core (706). The spacing between individual cores (702(1), 702(2)) may vary depending on the radius and access requirements for coolant routing. Any suitable number of heat exchanger cores (702) may be provided and piped in any suitable configuration, such as in series, in parallel, or a combination thereof.

[0081] FIG. 8 illustrates an exemplary stacked configuration (800) for heat exchanger cores (802(1), 802(2), 802(n)). The heat exchanger cores (802) may be as substantially described herein for heat exchanger embodiments and may be oriented horizontally, vertically, or in some other orientation. The cores (802) may be arranged circumferentially and / or radially around the reactor vessel. As illustrated, in some cases, two or more cores (802) may be stacked vertically on top of each other. In some cases, a flow path from the reactor vessel hot pool may enter the core (802) of the upper column (804) and additionally enter the core (806) of the lower column to define a parallel path and / or multiple inlets from the reactor core hot pool to the core (802).

[0082] As with all exemplary configurations of multiple heat exchanger cores (802), individual cores may be piped in series, in parallel, or a combination thereof. In the illustrated stacked configuration (800), the first heat exchanger body (808) may include a core (802) of the upper column (804), and the second heat exchanger body (810) may include a core (802) of the lower column (806). Each column may have an inlet separated from the reactor vessel hot pool so that the primary coolant can circulate within the reactor vessel and enter the heat exchanger. The upper column (804) and the lower column (806) may likewise utilize a header (not shown) to guide the primary coolant into the core (802), or additionally or alternatively, utilize pipes to guide the primary coolant into one or more cores (802).

[0083] FIG. 9 illustrates exemplary locations of heat exchanger cores (902(1), 902(2), 902(n)) arranged circumferentially around the inner circumference of a reactor vessel (904). The cores (902) may be arranged as substantially described herein and, in some cases, located far from the reactor core (not shown). The relatively small size of the heat exchanger cores (902) and their proximity to high neutron activity regions within the reactor core allows the heat exchanger cores (902) to avoid much neutron activity, thereby requiring much less shielding than when the heat exchanger is much larger or defines a coolant flow path closer to the reactor core.

[0084] FIG. 10 illustrates the configuration (1000) of heat exchanger cores (1002(1), 1002(2), 1002(n)). The cores (1002) may substantially be as described herein in relation to the heat exchanger embodiments. The cores (1002) may be arranged circumferentially around the reactor vessel and may additionally be stacked in multiple rows. As illustrated, for a total of 20 cores (1002), there are 4 rows of cores (1002) stacked at a height of 5. Of course, fewer or more cores (1002) may be similarly arranged based on the heat load requirements of the reactor. Additional cores (1002) may be located in adjacent rows or additional columns, or separate heat exchanger configurations (1000) may include any suitable number of columns and / or rows located in different parts of the reactor vessel.

[0085] FIG. 11 illustrates a configuration (1100) of a heat exchanger core (1102) comprising any suitable number of columns and rows to accommodate the heat load of a reactor. The heat exchanger core may be substantially as described herein and may be designed to use any suitable piping arrangement, such as the heat exchanger core (1102) being piped in series, in parallel, or a combination thereof. As illustrated, the heat exchanger configuration (1100) may include a low-temperature header (1104), a high-temperature header (1106), and piping (1108) defining a flow path for fluids to enter and exit the heat exchanger core (1102). The core (1102) may be oriented in any suitable orientation, such as horizontal, vertical, or any suitable angle, as illustrated. In some cases, the outlet of the first heat exchanger core is fluidly connected to the inlet of the second heat exchanger core, so that the first and second heat exchanger cores are piped in series with each other.

[0086] The low temperature header (1104) and the high temperature header (1106) can be used to form a fluid path for a secondary coolant, which may be salt. In some cases, the core has individual inlets that allow a circulating primary coolant (which may be sodium) to enter individual heat exchanger cores.

[0087] FIG. 12 illustrates an exemplary orientation and position for the heat exchanger core (1102) of FIG. 11. The reactor (1200) comprises a reactor vessel (1202) and one or more pumps (1204). The pump (1204) can send primary coolant within the reactor vessel to the heat exchanger core (1102). In some cases, the pump (1204) directs primary coolant from the hot pool to the heat exchanger, for example, by pressurizing the primary coolant into a plenum that is fluidly communicating with one or more heat exchanger core inlets.

[0088] As illustrated, the heat exchanger core (1102) is located near the top of the reactor vessel (1202), which is a region of low neutron activity. Thus, the secondary coolant, which may be a salt in some cases, is activated to a much lower degree than a conventional heat exchanger defining a flow path near the reactor core. Furthermore, the compact configuration of the heat exchanger core requires much less shielding (1206) to protect the secondary coolant from neutron activation. Additionally, in some embodiments, the described heat exchanger core and their various locations within the reactor vessel allow for a sodium-salt heat exchanger that improves the salt activation problem within the reactor vessel.

[0089] According to the configuration of the heat exchanger cores described in this specification, individual cores may be structurally supported individually, which mechanically separates one heat exchanger core from another and allows the individual cores to twist and expand independently of each other. Thus, the heat exchanger cores handle thermal stress individually but can remain fluidly coupled together.

[0090] Typically, an intermediate loop is provided within the SFR in which primary sodium transfers thermal energy to an intermediate sodium loop. The intermediate sodium loop then transfers thermal energy to a third loop, which may contain water, salt, or other working fluids. By utilizing the compact heat exchanger shown and described herein, the intermediate loop can be eliminated, and thus a sodium-salt heat exchanger can be obtained that avoids many problems in conventional embodiments, such as the required size of the sodium / salt heat exchanger and the avoidance of salt activation.

[0091] As in any embodiment described herein, the heat exchanger core may define a third fluid flow path between the high-temperature flow path and the low-temperature flow path. The third fluid flow path may be used for leak detection and separation of the primary coolant from the secondary coolant. When the third fluid is discharged from the heat exchanger, the presence of the primary or secondary coolant may be tested. For example, helium may pass through the third fluid flow path and the presence of the primary or secondary coolant may be tested at its outlet.

[0092] In some examples, a third fluid flow path can be used to promote oxidation of the high and low temperature plates within the heat exchanger core. For example, an oxidizing fluid such as CO2 can pass through the third fluid flow path to form an oxide layer within the flow channel. The oxide layer has been shown to inhibit the movement of activating products such as tritium.

[0093] In some cases, an oxide layer may form within the heat exchanger core during the manufacturing process. For example, when forming heat exchange core plates, an oxide layer may be formed on the plates before they are bonded together by laminating materials onto the plates through additive manufacturing, vapor deposition, printing, or some other material lamination process.

[0094] Additionally, a third fluid flow path may be used to attract an activating product, such as tritium. For example, a fluid such as helium may pass through a third fluid path capable of capturing tritium before passing through a salt. Tritium may be attracted more to the third fluid than to the secondary coolant. The captured tritium can then be removed from the helium. The method may include the step of forming a heat exchanger core having a first fluid flow path, a second fluid flow path, and a third fluid flow path. The method may include the step of passing a selected third fluid through the third fluid flow path to attract an activating product, such as tritium. The method may further include the step of recovering the third fluid after it has passed through the heat exchanger core and then isolating the activating product. In some cases, the method may include the step of passing a fourth fluid through the third fluid flow path, and the fourth fluid may be used for other purposes, such as leak detection, the formation of an oxide layer, or some other purpose.

[0095] In this description, the terms "heat exchanger" and "heat exchanger core" are used. In some cases, a heat exchanger may consist of one or more heat exchanger cores. Since a single core can function as a standalone heat exchanger independently of other heat exchanger cores, the terms may be used interchangeably. In some cases, multiple heat exchanger cores may cooperate and be referred to as a plural heat exchanger.

[0096] This disclosure describes exemplary embodiments and is not intended to limit the scope of this disclosure and the appended claims in any way. Several embodiments have been described above with the help of functional configuration blocks that exemplify the implementation of specific components, functions, and their relationships. The boundaries of these functional configuration blocks are defined arbitrarily herein for convenience of explanation. Other boundaries may be defined within the scope in which the specified functions and their relationships are appropriately performed.

[0097] The foregoing description of specific embodiments will sufficiently reveal the general characteristics of the embodiments of this disclosure so that others, by applying the knowledge of those skilled in the art, can easily modify and / or adapt them for various applications such as specific embodiments without excessive experimentation and without departing from the general concept of the embodiments of this disclosure. Accordingly, such adaptations and modifications are intended to be within the meaning and scope of equivalents of the disclosed embodiments based on the teachings and guidelines set forth herein. Since the expressions or terms of this specification are for descriptive purposes only, the terms or expressions of this specification should be interpreted by those skilled in the art in light of the teachings and guidelines set forth herein.

[0098] The breadth and scope of the embodiments of the present disclosure shall not be limited by the exemplary embodiments described above, but shall be defined only by the following claims and their equivalents.

[0099] For example, above all, conditional language such as “can” is generally intended to mean that a particular embodiment may include certain features, elements, and / or behaviors that other embodiments do not include, unless otherwise specifically stated or otherwise understood within the context in which they are used. Accordingly, such conditional language is generally not intended to mean that features, elements, and / or behaviors are required in one or more embodiments in some way, or that one or more embodiments must include logic for determining whether such features, elements, and / or behaviors are included in any particular embodiment or performed by such embodiment, regardless of the presence or absence of user input or prompts.

[0100] Those skilled in the art will recognize that any process or method disclosed herein may be modified in various ways. The process parameters and sequence of steps described and / or illustrated herein are provided merely as examples and may be changed as desired. For example, steps exemplified and / or described herein may be illustrated or discussed in a specific order, but such steps are not required to be performed in the order exemplified or discussed.

[0101] Various exemplary methods described and / or illustrated in this specification may also omit one or more of the steps described or illustrated in this specification, or include additional steps in addition to the disclosed steps. Additionally, steps of any method disclosed in this specification may be combined with any one or more steps of any other method disclosed in this specification.

[0102] Of course, for the purpose of describing the various features of this disclosure, it is not possible to describe all possible combinations of elements and / or methods, but those skilled in the art recognize that many additional combinations and permutations of the disclosed features are possible. Accordingly, various modifications to this disclosure may be made without departing from the scope or spirit of this disclosure. Furthermore, other embodiments of this disclosure may be derived from the practice of the disclosed embodiments presented herein by considering the specification and the accompanying drawings. The examples presented in the specification and the accompanying drawings should be considered illustrative in all respects and not restrictive. Even if specific terms are used in this specification, they are used only in a comprehensive and descriptive sense and are not intended to be restrictive.

[0103] Unless otherwise specified, the terms “connected,” “combined,” and “fluid-connected” (and their derivatives) as used in this specification shall be interpreted as allowing both direct and indirect connections (i.e., through other elements or components). Additionally, the singular forms of terms used in this specification shall be interpreted as meaning “at least one of.” Finally, for convenience of use, the terms “comprising” and “having” (and their derivatives) as used in this specification are interchangeable with and have the same meaning as the word “constituting.”

[0104] From the foregoing description and the attached drawings, while specific embodiments have been described for illustrative purposes, it will be understood that various modifications may be made without departing from the spirit and scope of the appended claims and the elements cited therein. Furthermore, while specific embodiments are presented below in the form of specific claims, the inventor considers various embodiments in any available claim form. For example, some embodiments may be cited as being implemented in a specific configuration, but other embodiments may likewise be implemented in such a way. Various modifications and alterations may be made as will be obvious to those skilled in the art having an interest in the present disclosure. This is intended to include all such modifications and alterations, and therefore the foregoing description should be considered illustrative rather than restrictive.

Claims

Claim 1 A plate heat exchanger for a nuclear reactor, comprising: a plurality of plates; a first fluid inlet, a first fluid outlet, and a first fluid path formed as a guide channel in the plurality of plates that fluidly communicates between the first fluid inlet and the first fluid outlet; a second fluid path formed as a second guide channel in the plurality of plates that fluidly communicates between the second fluid inlet and the second fluid outlet, comprising a second fluid inlet, a second fluid outlet, and a second fluid path formed as a second guide channel in the plurality of plates and not fluidly communicating with the first fluid path. A plate-type heat exchanger comprising a third fluid inlet, a third fluid outlet, and a third fluid path, wherein the third fluid path is fluidly connected between the third fluid inlet and the third fluid outlet, is not fluidly connected to the first fluid path and the second fluid path, and is configured for purposes other than heat energy transfer, wherein the third fluid path is configured to accommodate a third fluid different from the first fluid and the second fluid, and the third fluid is used to create an oxide layer within the third fluid path. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 A plate-type heat exchanger according to claim 1, wherein the first fluid inlet and the first fluid outlet are formed on the same side of the plate-type heat exchanger. Claim 10 A plate-type heat exchanger according to claim 9, further comprising a coaxial conduit coupled to the first fluid inlet and the first fluid outlet, wherein the coaxial conduit defines an inner fluid conduit and an outer fluid conduit, wherein the inner fluid conduit is coupled to one of the first fluid inlet and the first fluid outlet in fluid communication, and the outer fluid conduit is coupled to the other of the first fluid inlet and the first fluid outlet in fluid communication. Claim 11 A plate-type heat exchanger according to claim 1, further comprising a first fluid in the first fluid path and a second fluid in the second fluid path. Claim 12 A plate-type heat exchanger according to claim 11, wherein the first fluid is sodium. Claim 13 A plate-type heat exchanger according to claim 11, wherein the second fluid is a molten salt. Claim 14 A plate-type heat exchanger according to claim 1, wherein the plate-type heat exchanger is a first plate-type heat exchanger and further comprises a second plate-type heat exchanger coupled to the first plate-type heat exchanger in fluid communication. Claim 15 A plate-type heat exchanger according to claim 14, wherein the first fluid outlet of the first plate-type heat exchanger is fluidly connected to the first fluid inlet of the second plate-type heat exchanger. Claim 16 A plate-type heat exchanger according to claim 1, wherein the plate-type heat exchanger is a first plate-type heat exchanger and further comprises a plurality of heat exchangers configured to cooperate to handle the heat load of a nuclear reactor. Claim 17 A plate-type heat exchanger according to claim 16, wherein at least some of the plurality of heat exchangers are fluidly connected by a fluid header. Claim 18 A plate-type heat exchanger in which at least some of the plurality of heat exchangers are piped in series, as in Clause 16. Claim 19 A plate-type heat exchanger in which at least some of the plurality of heat exchangers are piped in parallel in Clause 16. Claim 20 A method for removing fission products or activation products from a reactor coolant within a heat exchanger of a reactor, comprising: positioning a plate-type heat exchanger within a reactor vessel; passing a primary coolant through a first fluid path of the plate-type heat exchanger; passing a secondary coolant through a second fluid path of the plate-type heat exchanger; passing a third fluid through a third fluid path of the plate-type heat exchanger, wherein the third fluid is selected to attract the fission products or activation products; and removing the fission products or activation products together with the third fluid from the plate-type heat exchanger. Claim 21 A method according to claim 20, comprising the step of recovering the third fluid after the third fluid passes through a heat exchanger core, and isolating fission products or activation products from the recovered third fluid. Claim 22 A method according to claim 20, comprising the step of selecting the third fluid as hydrogen, helium, or hydrogen and helium, wherein the fission product or activation product includes tritium, so that tritium preferentially moves to the third fluid instead of the secondary coolant. Claim 23 A method according to claim 20, comprising the step of selecting sodium as the primary coolant and the step of selecting molten salt as the secondary coolant. Claim 24 A method according to claim 20, comprising the step of passing a fourth fluid through a third fluid path, wherein the fourth fluid is selected to form an oxide layer on the inner surface of a plate-type heat exchanger in contact with a primary coolant or a secondary coolant. Claim 25 A method according to claim 20, comprising the step of analyzing a third fluid downstream of a plate-type heat exchanger to detect the presence of a primary coolant or a secondary coolant in the third fluid as an indication of leakage between a primary fluid path and a secondary fluid path. Claim 26 A method according to claim 20, comprising radially separating a plate heat exchanger from the reactor core and placing it on top of the reactor vessel to reduce neutron activation of the secondary coolant. Claim 27 A method according to claim 20, comprising arranging plate-type heat exchangers within a reactor vessel and passing a primary coolant through at least two plate-type heat exchangers arranged in series or parallel, such that each plate-type heat exchanger passes through only a portion of the total temperature change between the inlet and outlet of the primary coolant.

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