Method and system for isotopic lithium separation

Abstract

A method and system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7. The method involves using molecular distillation with heat exchange means supplied by a nuclear reactor (1) for efficient separation of isotopes. The system comprises a molecular distillation apparatus with a distiller (20) and incorporates a nuclear reactor (1) equipped with heat exchange means to provide the heat required for the process.

Description

Technical Field

[0001] This disclosure relates to methods and systems for isotopic lithium separation of lithium-7 and lithium-6, and particularly to methods and systems for isotopically separating lithium-7 and lithium-6 from naturally occurring lithium. Background Technology

[0002] Due to the geological isotopic separation of lithium-7 and lithium-6, naturally occurring lithium is a mixture of lithium-7 and lithium-6 in different proportions, with the lithium-6 concentration varying from approximately 2% to 8%, of which 5% is the norm.

[0003] Molten salt reactors utilizing lithium fluoride or lithium chloride salts actually require highly enriched lithium-7 because lithium-6 and lithium-7 have significantly different thermal neutron capture cross-sections (941 peons and 0.014 peons for thermal neutrons, respectively), and this is partly to minimize tritium production from neutron capture from lithium-6.

[0004] Naturally occurring lithium has a thermal capture cross-section of approximately 65 peons, which is very high compared to, for example, naturally occurring sodium with a thermal capture cross-section of 0.5 peons or naturally occurring potassium with a thermal capture cross-section of 2 peons. For comparison, 99.9% enriched lithium-7 (3N7Li) has a thermal capture cross-section of 0.95 peons, 99.99% enriched lithium-7 (4N7Li) has a thermal capture cross-section of 0.11 peons, and 99.999% enriched lithium-7 (5N7Li) has a thermal capture cross-section of 0.02 peons. This means that when using lithium in molten salt reactor salts, 99.99% to 99.999% enriched lithium-7 (4-5N7Li) is desirable.

[0005] Examples of lithium fluoride salts that can be used in molten salt reactors are 7LiF-BeF2, 7LiF-BeF2-UF4, 7LiF-ThF4, 7LiF-ThF4-UF4, and 7LiF-ThF4-PuF3. Examples of lithium chloride salts that can be used in molten salt fast reactors are 7LiCl-KCl-UCl3, 7LiCl-UCl3, 7LiCl-PuCl3, and 7LiCl-UCl3-PuCl3.

[0006] Highly enriched lithium-7 is particularly important for molten salt breeder reactors, which have the potential to scale up faster than other nuclear technologies when fission fuel supplies are limited. To scale up molten salt breeder reactors to meet global energy demands over the coming decades, tens of thousands of tons of lithium-7 enrichment capacity per year will be needed, posing a significant challenge to scaling up this type of reactor.

[0007] When lithium-6 captures thermal neutrons, there is a high probability that it will lead to tritium production. Tritium production from lithium-6 is considered a radioactive nuclide release hazard in nuclear reactors, and is a target in the blankets of some fusion reactors. Therefore, nuclear (fission) reactors utilizing lithium require enriched lithium-7, while fusion reactors require enriched lithium-6, and lithium isotope separation can synergistically serve both industries.

[0008] Examples of fluoride salts that can be used as fusion reactor blanket salts are 6LiF-BeF2 and 6LiF-7LiF-BeF2, in which beryllium is also used as a neutron multiplier, and examples of molten metal alloys that can be used as fusion reactor blankets are Li, Li-Pb and Li-Bi.

[0009] The primary method for industrialized isotopic lithium separation is the COLEX process, a two-liquid-phase chemical exchange between an aqueous lithium hydroxide solution and a mercury-lithium amalgam, where lithium-6 has a slightly higher affinity for the amalgam. The COLEX process involves large amounts of mercury and mercury compounds, which, along with its high energy consumption, makes it unattractive for future isotopic lithium separation.

[0010] The COLEX process is a mercury-based chemical method for isotopic separation of lithium-6 and lithium-7, in which an aqueous lithium hydroxide (LiOH) solution is contacted with a lithium-mercury amalgam, taking advantage of the greater affinity of lithium-7 for elemental mercury than lithium-6. The COLEX separation process involves passing a countercurrent aqueous lithium hydroxide solution upwards and the lithium-mercury amalgam downwards through a series of exchange columns containing cation exchange resins. Mercury preferentially exits the lithium-6 fraction, although lithium-7 flows primarily with the hydroxide. At the bottom of the columns, the amalgam is separated from the lithium (enriched with lithium-6), and the mercury is recovered for subsequent use. At the top, the lithium-7 fraction is electrolyzed to release the lithium hydroxide solution. Operating temperature, flow rate, and column length all affect the enrichment achievable by this process.

[0011] The facility in Oak Ridge, Tennessee, using the COLEX process operated between 1955 and 1963 to produce the 6Li and 7Li currently stored in the United States.

[0012] COLEX has several drawbacks, such as: - The toxicity of the large quantities of mercury involved; - The tendency of amalgam to decompose in aqueous solution; - This creates hazardous mercury-containing waste; - High energy consumption; - Potentially catastrophic environmental impacts, due to the need for large quantities of mercury (24 million pounds were used in the United States between 1955 and 1963) and numerous opportunities for leakage into the environment.

[0013] Numerous methods for lithium isotope separation have been studied and developed, including two-liquid-phase chemical exchange, ion-exchange resins, ion-exchange membranes, laser absorption, thermal diffusion, electromigration, fractional crystallization, microalgae, and molecular distillation. While many of these methods have been proven operational, none have yet demonstrated an economical alternative to the COLEX process.

[0014] Research on isotopic separation of lithium metal using molecular distillation was limited, with only a few articles published in the late 1950s and early 1960s, and the process was eventually abandoned, partly due to the high energy and temperature requirements of the technique.

[0015] CN115193253 discloses a method and apparatus for separating isotopes 6Li and 7Li using molecular distillation. Based on the difference in atomic mass between 6Li and 7Li, 6Li and 7Li are separated by thermal evaporation. The method is characterized in that, in a vacuum chamber, after native lithium metal is heated and evaporated, and the lithium vapor is maintained at a certain pressure and reaches thermal equilibrium, 6Li is mainly distributed in the upper part of the vacuum chamber, and 7Li is mainly distributed in the lower part. The boundary between the 6Li and 7Li vapors can be determined based on the content ratio of 6Li and 7Li in native lithium metal, temperature, and pressure. Furthermore, a separator plate is provided at the boundary between the 6Li and 7Li vapors, which can be inserted or removed as needed. During thermal equilibrium, the separator plate is inserted, and then the 6Li and 7Li vapors are separated. <n>They are released into their respective cooling containers to be cooled into solids, and a protective layer is added to enable the separation of 6Li and 7Li. Summary of the Invention

[0016] The purpose of this invention is to provide a method and system for isotopic lithium separation that overcomes or at least mitigates the above-mentioned problems.

[0017] The foregoing and other objectives are achieved through the features of the independent claims. Further implementations are apparent from the dependent claims, the specification, and the drawings.

[0018] Lithium metal melts at 180°C and boils at 1330°C; therefore, simple distillation seems unattractive due to the high boiling point of molten lithium and the low separation factor at high temperatures. However, the inventors recognized that at temperatures far below the boiling point of lithium, the separation factor is sufficient for effective isotope separation due to the high molecular weight difference between molten lithium-6 and lithium-7. The molecular weight difference between lithium-6 and lithium-7 is sufficient to achieve a theoretical separation factor of 1.08, where the difference in vapor pressure is relatively small in comparison.

[0019] For effective molecular distillation, the mean free path length of vapor atoms or molecules must be on the same order of magnitude as or longer than the distance between the evaporation and condensation surfaces. The mean free path length of lithium atoms will depend on the vacuum quality of the still and the lithium vapor pressure, which in turn depends on the temperature of lithium. The mean free path length of lithium vapor is approximately 50 mm at 400°C, approximately 20 mm at 500°C, and approximately 15 mm at 550°C. Since the free path length is longer at lower temperatures, molecular distillation is generally more efficient at lower temperatures, but the distillation rate will also be lower due to the lower evaporation rate. Therefore, a balance needs to be found between distillation efficiency and distillation rate for a specific still. The inventors have determined that for lithium molecular distillation, the optimal evaporation surface temperature is approximately 500°C to 600°C, with the cold side temperature being approximately 100°C lower, i.e., approximately 400°C to 500°C.

[0020] The inventors have observed that short-path molecular distillation of lithium in liquid form is attractive because it allows for multiple stages with very short paths between the evaporation and condensation surfaces. Furthermore, the inventors have observed that, since molten lithium is compatible with common stainless steel, the still can be constructed using conventionally available materials and manufacturing methods. However, this type of still requires heating the bottom of the still while cooling the top at each stage, making it energy-intensive.

[0021] According to a first aspect, a method is provided for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the method comprising: - Using a molecular distillation apparatus, the feed stream of molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 is isotopically separated into an enriched molten lithium-6 stream and an enriched molten lithium-7 stream by molecular distillation, the molecular distillation apparatus comprising a distiller or a series of distillers; - Using a nuclear reactor to heat the heat exchange medium to a temperature of at least 400°C; and - The heated heat exchange medium is supplied to the molecular distillation equipment.

[0022] By using a nuclear reactor to provide heat for the molecular distillation process, the inherently energy-intensive process becomes less expensive due to the readily available and relatively inexpensive high-temperature heat from the nuclear reactor, thus significantly reducing the cost of molecular distillation and making it economically competitive with other known methods for isotopic lithium separation.

[0023] According to the possible implementation of the first aspect, a nuclear reactor is one of the following: - A gas-cooled reactor, preferably a high-temperature gas-cooled reactor (HTGR) or an ultra-high-temperature reactor (VHTR); - Liquid metal cooled reactor (LMR); - Heat pipe cooled reactor (HPR); - Molten Salt Reactor (MSR).

[0024] According to a possible implementation of the first aspect, the evaporator is operatively connected to the distiller, and the method includes supplying a heated heat exchange medium to the evaporator.

[0025] According to a possible implementation of the first aspect, the nuclear reactor includes: a reactor core; a first-stage heat exchange loop containing a first-stage heat exchange medium, the first-stage heat exchange loop passing through the reactor core and through a first-stage heat exchanger; and a second-stage heat exchange loop containing a second-stage heat exchange medium, the second-stage heat exchange loop passing through the first-stage heat exchanger, the method comprising transferring heat from the reactor core to the second-stage heat exchange medium by circulating the first-stage heat exchange medium in the first-stage heat exchange loop and by circulating the second-stage heat exchange medium in the second-stage heat exchange loop.

[0026] According to a possible implementation of the first aspect, the second-stage heat exchange loop passes through an evaporator.

[0027] According to a possible implementation of the first aspect, the distiller includes one or more of the following: - Vertical column still; - Horizontal still; - A vacuum port for connecting to a vacuum system used for drawing high or ultra-high vacuum; - A feed port for receiving a mixture of molten lithium; - Return port; - First upper outlet port for enriched lithium-6 vapor; - Second lower outlet port for enrichment of molten lithium-7; - Heating elements; - Thermal insulation components.

[0028] According to a possible implementation of the first aspect, the evaporator is operably connected to the distiller, and the heat exchange medium supplying heat to the evaporator comprises a molten salt having a suitable melting point and boiling point, preferably a nitrate, fluoride, or chloride salt.

[0029] According to a possible implementation of the first aspect, the condenser is operatively coupled to the distiller, and the method includes removing heat from the condenser using a heat exchange medium, preferably, the method includes removing heat from the condenser using a molten salt, preferably, the molten salt being a nitrate, fluoride, or chloride salt.

[0030] According to a possible implementation of the first aspect, the heat exchange medium circulates in a loop in which one or more intermediate heat exchangers are arranged between the evaporator and the condenser, the method comprising increasing the temperature drop between the evaporator and the condenser, preferably, the one or more intermediate heat exchangers comprising countercurrent heat exchangers.

[0031] According to a possible implementation of the first aspect, the heat exchange medium comprises a NaNO3-KNO3 eutectic salt with a melting point of about 250°C, and the method comprises heating the evaporator to at least about 400°C, preferably, the method comprises heating the evaporator to about 550°C, and the NaNO3-KNO3 eutectic salt has a maximum operating temperature of 560°C due to thermal decomposition at a higher temperature.

[0032] According to a possible implementation of the first aspect, the method includes cooling the condenser to about 300°C, preferably, the method includes cooling the condenser to about 260°C.

[0033] According to a possible implementation of the first aspect, the method includes heating the evaporator to about 400°C and cooling the condenser to about 150°C using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C. Preferably, the method includes heating the evaporator to about 550°C and cooling the condenser to about 150°C using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C, the LiNO3-NaNO3-KNO3 eutectic salt having a maximum operating temperature of 560°C due to thermal decomposition.

[0034] According to a possible implementation of the first aspect, the method includes using a LiF-NaF-KF eutectic salt with a melting point of about 450°C, the method including heating the evaporator to about 600°C and cooling the condenser to about 500°C using a LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt, wherein the LiF-NaF-KF eutectic salt is preferably operated at a maximum operating temperature of 700°C to prevent excessive corrosion of the salt container material.

[0035] According to a possible implementation of the first aspect, the method includes heating the evaporator with LiF-NaF-KF or NaNO3-KNO3 salt and cooling the condenser with an organic coolant.

[0036] According to a possible implementation of the first aspect, the distiller includes packing material, preferably structured packing material, and / or wherein the distiller is a vertical distiller.

[0037] According to a second aspect, a system is provided for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the system comprising: - Molecular distillation apparatus, said molecular distillation apparatus comprising: At least one distiller is configured to isotopically separate a feed stream of molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 into a stream enriched in molten lithium-6 and a stream enriched in molten lithium-7. An evaporator, the evaporator being operatively connected to the at least one distillation apparatus; - A nuclear reactor, the nuclear reactor comprising a reactor core; The system includes a heat exchange device for transferring heat from the nuclear reactor core to an evaporator using at least one heat exchange medium, the heat exchange device being configured to supply heat to the evaporator with a heat exchange medium having a temperature of at least 400°C.

[0038] According to a possible implementation of the second aspect, the nuclear reactor includes: A first-stage heat exchange loop comprising a first-stage heat exchange medium, the first-stage heat exchange loop passing through the reactor core and through a first-stage heat exchanger; and A second-stage heat exchange loop containing a second-stage heat exchange medium, the second-stage heat exchange loop being connected to the first-stage heat exchanger.

[0039] According to a possible implementation of the second aspect, the distiller includes one or more of the following: - Vertical column still; - Horizontal still; - A vacuum port for connecting to a vacuum system used for drawing high or ultra-high vacuum; - A feed port for receiving a mixture of molten lithium; - Return port; - First upper outlet port for enriched lithium-6 vapor; - Second lower outlet port for enrichment of molten lithium-7; - Heating elements; - Thermal insulation components.

[0040] According to a third aspect, a method is provided for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the method comprising: - Using a molecular distillation apparatus, a molten lithium metal material containing a mixture of lithium-6 and lithium-7 is isotopically separated into enriched molten lithium-6 and enriched molten lithium-7 by molecular distillation, the molecular distillation apparatus comprising a distiller or a series of distillers; - Using a nuclear reactor to heat the heat exchange medium to a temperature of at least 400°C; and - The heated heat exchange medium is supplied to the molecular distillation equipment to drive the molecular distillation process.

[0041] According to a second aspect, a system is provided for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the system comprising: - Molecular distillation apparatus, said molecular distillation apparatus comprising: At least one distiller is configured to isotopically separate a mixture of lithium-6 and lithium-7 into enriched molten lithium-6 and enriched molten lithium-7. An evaporator, the evaporator being operatively connected to the at least one distillation apparatus; - A nuclear reactor, the nuclear reactor comprising a reactor core; The system includes a heat exchange device for transferring heat from the nuclear reactor core to an evaporator using at least one heat exchange medium, the heat exchange device being configured to supply heat to the evaporator with a heat exchange medium having a temperature of at least 400°C.

[0042] These and other aspects will become apparent from the embodiments and implementations described below. Attached Figure Description

[0043] In the following detailed sections of this disclosure, aspects, implementation methods, and methods of implementation will be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, wherein: Figure 1 This is a schematic diagram of a system including a molecular distillation apparatus and a nuclear reactor, according to an embodiment. Figure 2 This is a schematic diagram of a system including a molecular distillation apparatus and a nuclear reactor according to another embodiment, and Figure 3 This is a schematic diagram of yet another system including a molecular distillation apparatus and a nuclear reactor, according to another embodiment. Detailed Implementation

[0044] Figure 1 An embodiment of a system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7 by molecular distillation is shown. The system includes a molecular distillation apparatus and a nuclear reactor 1. The molecular distillation apparatus includes at least one distiller 20 configured to isotopically separate a feed stream containing a mixture of lithium-6 and lithium-7 into a stream enriched in molten lithium-6 and a stream enriched in molten lithium-7. The molecular distillation apparatus may include multiple distillers 20 connected in series. Figure 1 In the illustrated embodiment, the distiller 20 includes a vertical column 22, a vacuum port 29 for connection to a vacuum system 40 for drawing a high or ultra-high vacuum, a feed port 24 for receiving a mixture of molten lithium, a reflux port 26, a first upper outlet port 27 for enriched lithium-6 vapor, a second lower outlet port 28 for enriched molten lithium-7, structured packing 23, a heating element 31, and a thermal insulation element 32. However, it should be understood that this is merely an example of a distiller 20 that can be used in a distillation apparatus, and other types of distillers, such as horizontal distillers (not shown), can also be used. The molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 is fed into the vertical column 22 through a feed pipe leading to the feed port 24, preferably as a substantially constant flow, but this can also be an intermittent flow. The vacuum port 29 is connected to a vacuum pump 4, which generates a high or ultra-high vacuum inside the vertical column 22. Evaporator 25 is operably connected to distiller 20 at two separate locations via evaporator conduit 29, which has an inlet located at the lowest region of vertical column 22 and an outlet located slightly above the lowest region of vertical column 22. In this embodiment, the inlet of evaporator conduit 29 is connected to a second lower outlet 28; however, it should be understood that evaporator 29 may also have its own port into the lowest region of vertical distillation column 22. The enriched molten lithium-7 is circulated through evaporator conduit 29 and evaporator 25 via a circulation pump (not shown) or other means capable of forcing the circulation of molten lithium-7.

[0045] The packing material 23, preferably structured packing 23, provides a large surface area for countercurrent molten lithium metal and lithium metal vapor. The structured packing material 23 is preferably optimized for short-range molecular distillation of lithium, with the operating temperature of the distiller 20 taken into account in the design of the structured packing 23. Relatively long sections of packing 23 act as multiple theoretical stages, thereby achieving a large separation factor in one or more sections of packing 23. The distillation process occurs above the melting point of molten lithium, but preferably below the boiling point of molten lithium.

[0046] The first upper outlet 27 is connected to the inlet of the condenser 30, and the outlet of the condenser 30 is divided into a reflux 26 and a side flow 21 for the enriched molten lithium-6.

[0047] Condenser 30 is operatively coupled to distiller 20 for removing heat from the enriched lithium-6 vapor stream from upper outlet 27, thereby causing at least partial condensation of the enriched lithium-6 vapor stream from upper outlet 27 in condenser 30. Condenser 30 is cooled using a heat exchange medium to remove heat from condenser 30. In embodiments, the exchange medium is a molten salt, preferably a nitrate, fluoride, or chloride salt.

[0048] The system includes a heat exchange device for transferring heat from nuclear reactor 1 to evaporator 25 using at least one heat exchange medium, the heat exchange device being configured to supply heat to evaporator 25 with a heat exchange medium having a temperature of at least 400°C supplied to the heat exchange device.

[0049] The nuclear reactor 1 includes: a reactor core 2; and a first-stage heat exchange loop 3 containing a first-stage heat exchange medium, the first-stage heat exchange loop 3 passing through the reactor core 2 and through a first-stage heat exchanger 4. The first-stage heat exchange loop 3 includes a first-stage circulation pump 5, the first-stage circulation pump being used to circulate the first-stage heat exchange medium in the first-stage heat exchange loop 3.

[0050] The system includes a second-stage heat exchange loop 12 containing a second-stage heat exchange medium. The second-stage heat exchange loop 12 passes through a first-stage heat exchanger 4 and an evaporator 25, and is used to transfer heat from the nuclear reactor 1 to the evaporator 25. A circulation pump (not shown) may be installed in the second-stage heat exchange loop 12.

[0051] To provide the heat required for the molecular distillation process, the second-stage heat exchange medium is heated to approximately 400°C or higher using nuclear reactor 1.

[0052] Nuclear reactor 1 can be: a gas-cooled reactor, such as a high-temperature gas-cooled reactor (HTGR) or a very high-temperature reactor (VHTR); a liquid metal-cooled reactor (LMR); a heat pipe-cooled reactor (HPR); or a molten salt reactor (MSR). Therefore, the first heat exchange medium can be gas, liquid metal, or molten salt, and the second heat exchange medium can be gas, liquid metal, or molten salt, and any combination of materials used for the first and second heat exchange media can be used.

[0053] Therefore, the heated second-stage heat exchange medium is supplied to the molecular distillation apparatus, where the heated second-stage heat exchange medium is used in the evaporator 25 to drive the isotope separation process.

[0054] In this embodiment, the second-stage heat exchange medium used in the evaporator 25 includes or is a molten salt having a suitable melting point and boiling point, such as a NaNO3-KNO3 eutectic salt with a melting point of about 250°C. The evaporator 25 is heated to at least about 400°C, preferably to about 550°C.

[0055] In another embodiment, the second-stage heat exchange medium used in evaporator 25 includes, or is, a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°.

[0056] In another embodiment, the second-stage heat exchange medium used in the evaporator 25 comprises a LiF-NaF-KF eutectic salt with a melting point of about 450°C to heat the evaporator to about 600°C, preferably to about 700°C.

[0057] Figure 2 Another embodiment of a system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7 by molecular distillation is shown. In this embodiment, for simplicity, structures and features that are the same as or similar to those previously described or shown herein are indicated by the same reference numerals as previously used. This embodiment is substantially the same as the first embodiment, except that the second-stage heat exchange loop 12 passes through both the evaporator 25 and the condenser 30. Therefore, the same components and elements of the system and their functions are no longer described, but reference is made to the embodiment described above.

[0058] At least one intermediate heat exchanger 50 is arranged between the evaporator 25 and the condenser 30 to increase the temperature drop between them. The at least one intermediate heat exchanger 50 preferably comprises a counterflow recuperator. The heat removed from the intermediate heat exchanger 50 / counterflow heat exchanger can be used for other purposes, such as power generation or district heating. Another heat exchanger 52 may be arranged downstream of the condenser 30. The heat removed from the other heat exchanger 52 can be used for other purposes, such as power generation or district heating.

[0059] To cool the condenser 30, the heat exchange medium can be a molten salt, such as a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C, which allows the condenser to be cooled to about 150°C, preferably about 130°C.

[0060] Alternatively, a LiF-NaF-KF eutectic salt with a melting point of about 450°C can be used to heat the evaporator to about 600°C, preferably to about 700°C, and a LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt can be used to cool the condenser to about 550°C, preferably to about 400°C.

[0061] In some implementations, an organic coolant can be used to cool the condenser 30 while maintaining the high temperature required for isotope separation.

[0062] Figure 3 Another embodiment of a system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7 by molecular distillation is shown. In this embodiment, for simplicity, structures and features that are the same as or similar to those previously described or shown herein are indicated by the same reference numerals as previously used. This embodiment is substantially the same as the first embodiment, except that the second-stage heat exchange loop 12 is via a multi-stage horizontal distiller 62. Therefore, the same components and elements of the system and their functions are no longer described, but reference is made to the embodiment described above.

[0063] The heat exchange medium in the second-stage heat exchange loop 12 is heated to a high temperature in the first-stage heat exchanger 4 by exchanging heat with the heat exchange medium in the first-stage heat exchange loop 3. The high-temperature heat exchange medium leaving the first-stage heat exchanger 4 in the second-stage heat exchange loop 12 is fed into a lower passage extending along the lower horizontal side of the horizontal still 62 to heat the molten lithium in the lower portion of the horizontal still 62. From there, the heat exchange medium passes through a heat exchanger 54, where it exchanges heat with a cooling medium, causing the temperature of the heat exchange medium entering the upper portion of the horizontal still 62 to decrease. From the heat exchanger 54, the heat exchange medium is fed into an upper passage extending along the upper horizontal side of the horizontal still 62 and its condenser element 130, and from there, the heat exchange medium is fed back to the first-stage heat exchanger 4. Molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 is fed into the horizontal column 62 through a feed pipe leading to feed port 24 located in the lower portion of the horizontal still 62, preferably as a substantially constant flow, but this can also be a batch flow. The horizontal still comprises multiple horizontally distributed stages (three stages are shown as an example in this embodiment), but a still typically consists of more than 100 stages. Each still may include one or more trays, which in turn may include multiple stages. In the case of multiple trays, they are preferably connected to each other to provide a certain enrichment capacity. Molten lithium flows from one stage to the next through the bottom of each tray. The bottom of the tray is heated while the top is cooled to allow the lithium metal to evaporate across the bottom of the tray and condense on the top of the tray. The trays are configured such that the flow of lithium from one stage to another is in series. As lithium passes through the bottom of a stage, some lithium evaporates and condenses on the cap of that stage, forming the condenser element 130. This cap is tilted so that the condensed lithium metal falls into the bottom of the preceding stage. This drives the condensed lithium backward toward the first stage, while the condensed lithium dripping into the bottom of each stage displaces the forward-flowing molten lithium, and potentially the bottom of the tray is tilted to drive the molten lithium forward. In this way, a countercurrent flow of lithium is provided, wherein the condensed lithium rich in lithium-6 flows backward through each stage to the first outlet port 67, while the remaining lithium rich in lithium-7 flows forward through each stage toward the second outlet port 68. In this way, the enriched lithium-6 is concentrated at the beginning of the tray, and the enriched lithium-7 is concentrated at the end of the tray.

[0064] This document has described various aspects and implementations in conjunction with various embodiments. However, those skilled in the art, upon studying the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in practicing the claimed subject matter. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality.

[0065] The reference numerals used in the claims should not be construed as limiting the scope. Unless otherwise stated, the drawings should be read in conjunction with the description (e.g., crosshairs, arrangement of parts, scale, degree, etc.) and considered as part of the entire written description of this disclosure. As used in the description, the terms "horizontal," "vertical," "left," "right," "upper," and "lower," and their adjective and adverbial derivatives, refer only to the orientation of the illustrated structure when the particular drawing is facing the reader. Similarly, the terms "inward" and "outward" generally refer to the orientation of a surface relative to its axis of elongation or axis of rotation, as applicable.< / n>

Claims

1. A method for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the method comprising: - Using a molecular distillation apparatus, the feed stream of molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 is isotopically separated into an enriched molten lithium-6 stream and an enriched molten lithium-7 stream by molecular distillation of the feed stream of molten lithium metal feed material, the molecular distillation apparatus comprising a distiller (20) or a series of distillers (20). The method is characterized by comprising: - The heat exchange medium is heated to a temperature of at least 400°C using a nuclear reactor (1), and - The heated heat exchange medium is supplied to the molecular distillation equipment.

2. The method according to claim 1, wherein, The nuclear reactor is one of the following: - Gas-cooled reactor, preferably, the gas-cooled reactor is a high-temperature gas-cooled reactor or an ultra-high-temperature reactor; - Liquid metal cooled reactor; - Heat pipe cooled reactor; - Molten salt reactor.

3. The method according to claim 1 or 2, wherein, The evaporator (25) is operably connected to the distiller (20), the method comprising supplying a heated heat exchange medium to the evaporator (25).

4. The method according to any one of claims 1 to 3, wherein, The nuclear reactor (1) includes: a reactor core (2); a first-stage heat exchange loop (3) containing a first-stage heat exchange medium, the first-stage heat exchange loop (3) passing through the reactor core (2) and through a first-stage heat exchanger (4); and a second-stage heat exchange loop (12) containing a second-stage heat exchange medium, the second-stage heat exchange loop (12) passing through the first-stage heat exchanger (4), the method comprising transferring heat from the reactor core (2) to the second-stage heat exchange medium by circulating the first-stage heat exchange medium in the first-stage heat exchange loop (3) and by circulating the second-stage heat exchange medium in the second-stage heat exchange loop (12).

5. The method according to claim 4, wherein, The second-stage heat exchange loop (12) passes through the evaporator (25).

6. The method according to any one of claims 1 to 5, wherein, The distiller (20) includes one or more of the following: - Vertical column still (22); - Horizontal still (62); - Vacuum port (29), the vacuum port being used to connect to a vacuum system (40) for drawing high or ultra-high vacuum. - Feed port (24), the feed port being used to receive a mixture of molten lithium; - Return port (26); - First upper outlet port (27) for enriched lithium-6 vapor. - Second lower outlet port (28) for enrichment of molten lithium-7; - Heating element (31); - Thermal insulation element (32).

7. The method according to any one of claims 1 to 6, wherein, The evaporator (25) is operably connected to the distiller (20), and wherein the heat exchange medium supplying heat to the evaporator (25) comprises a molten salt having a suitable melting point and boiling point, preferably a nitrate, fluoride or chloride salt.

8. The method according to any one of claims 1 to 7, wherein, The condenser (30) is operatively connected to the distiller (20) in a manner that includes removing heat from the condenser (30) using a heat exchange medium, preferably, the method includes removing heat from the condenser (30) using a molten salt, preferably a nitrate, fluoride or chloride salt.

9. The method according to claim 8 when referring to claim 7, wherein, The heat exchange medium circulates in a loop (12) in which one or more intermediate heat exchangers (50) are arranged between the evaporator (25) and the condenser (30), the method comprising increasing the temperature drop between the evaporator (25) and the condenser (30), preferably, the one or more intermediate heat exchangers (50) comprising countercurrent heat exchangers (50).

10. The method according to any one of claims 7 to 9, wherein, The heat exchange medium includes a NaNO3-KNO3 eutectic salt, wherein preferably, the NaNO3-KNO3 eutectic salt has a melting point of about 250°C, and the method includes heating the evaporator (25) to at least about 400°C, preferably, the method includes heating the evaporator (25) to about 550°C.

11. The method of claim 10, wherein the method comprises cooling the condenser (30) to about 300°C, preferably, the method comprises cooling the condenser (30) to about 260°C.

12. The method according to any one of claims 7 to 9, wherein the method comprises heating the evaporator (25) to about 400°C and cooling the condenser (30) to about 150°C using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C, preferably, the method comprises heating the evaporator (25) to about 550°C and cooling the condenser (30) using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C. Cooling to about 150°C, preferably, the method includes heating the evaporator (25) to about 400°C and cooling the condenser (30) to about 130°C using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C, preferably, the method includes heating the evaporator (25) to about 550°C and cooling the condenser (30) to about 130°C using a LiNO3-NaNO3-KNO3 eutectic salt with a melting point of about 120°C.

13. The method according to any one of claims 7 to 9, wherein the method comprises heating the evaporator (25) to about 600°C using a LiF-NaF-KF eutectic salt with a melting point of about 450°C and cooling the condenser (30) to about 550°C using the LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt, preferably, the method comprises heating the evaporator (25) to about 700°C using a LiF-NaF-KF eutectic salt with a melting point of about 450°C and cooling the condenser (30) to about 550°C using the LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt. Cooling to about 550°C, preferably, the method includes heating the evaporator (25) to about 600°C using a LiF-NaF-KF eutectic salt with a melting point of about 450°C and cooling the condenser (30) to about 400°C using the LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt, preferably, the method includes heating the evaporator (25) to about 700°C using a LiF-NaF-KF eutectic salt with a melting point of about 450°C and cooling the condenser (30) to about 400°C using the LiF-NaF-KF salt or a LiNO3-NaNO3-KNO3 eutectic salt.

14. The method according to any one of claims 7 to 9, wherein the method comprises heating the evaporator (25) with LiF-NaF-KF or NaNO3-KNO3 salt and cooling the condenser (30) with an organic coolant.

15. The method according to any one of claims 1 to 14, wherein, The distiller (20) includes packing material (23), preferably, the packing material is structured packing material (23), and / or wherein the distiller (20) is a vertical distiller (20).

16. A system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the system comprising: - Molecular distillation apparatus, said molecular distillation apparatus comprising: At least one distiller (20) is configured to isotopically separate a feed stream of molten lithium metal feed material containing a mixture of lithium-6 and lithium-7 into an enriched molten lithium-6 stream and an enriched molten lithium-7 stream. An evaporator (25) is operatively connected to the at least one distillation apparatus (20). Its features are, - The system includes a nuclear reactor (1), which includes a reactor core (2). The system includes a heat exchange device for transferring heat from the nuclear reactor core (2) to the evaporator (25) using at least one heat exchange medium, the heat exchange device being configured to supply heat to the evaporator (25) with a heat exchange medium having a temperature of at least 400°C.

17. The system according to claim 16, wherein, The nuclear reactor includes a first-stage heat exchange loop (3) containing a first-stage heat exchange medium, the first-stage heat exchange loop (3) passing through the reactor core (2) and through a first-stage heat exchanger (4); and The system includes a second-stage heat exchange loop (12) containing a second-stage heat exchange medium, and the second-stage heat exchange loop (12) passes through the first-stage heat exchanger (4).

18. The system according to claim 16 or 17, wherein, The distiller (20) includes one or more of the following: - Vertical column still (22); - Horizontal still (62); - Vacuum port (29), the vacuum port being used to connect to a vacuum system (40) for drawing high or ultra-high vacuum. - Feed port (24), the feed port being used to receive a mixture of molten lithium; - Return port (26); - First upper outlet port (27) for enriched lithium-6 vapor. - Second lower outlet port (28) for enrichment of molten lithium-7; - Heating element (31); - Thermal insulation element (32).

19. A method for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the method comprising: - Using a molecular distillation apparatus, a molten lithium metal material containing a mixture of lithium-6 and lithium-7 is isotopically separated into enriched molten lithium-6 and enriched molten lithium-7 by molecular distillation, the molecular distillation apparatus comprising a distiller or a series of distillers; - Using a nuclear reactor to heat the heat exchange medium to a temperature of at least 400°C; and - The heated heat exchange medium is supplied to the molecular distillation equipment to drive the molecular distillation process.

20. A system for isotopically separating lithium-6 and lithium-7 from a mixture of lithium-6 and lithium-7, the system comprising: - Molecular distillation apparatus, said molecular distillation apparatus comprising: At least one distiller is configured to isotopically separate a mixture of lithium-6 and lithium-7 into enriched molten lithium-6 and enriched molten lithium-7. An evaporator, the evaporator being operatively connected to the at least one distillation apparatus; - A nuclear reactor, the nuclear reactor comprising a reactor core; The system includes a heat exchange device for transferring heat from the nuclear reactor core to the evaporator using at least one heat exchange medium, the heat exchange device being configured to supply heat to the evaporator with a heat exchange medium having a temperature of at least 400°C.

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