WO2018026536A1

WO2018026536A1 - Actinide recycling system

Info

Publication number: WO2018026536A1
Application number: PCT/US2017/043121
Authority: WO
Inventors: Michael F. SIMPSON; Andrew DODSON; William Wangard; Ed PHEIL; Michael Hanson
Original assignee: Elysium Industries Ltd
Current assignee: Elysium Industries Ltd
Priority date: 2016-07-20
Filing date: 2017-07-20
Publication date: 2018-02-08
Anticipated expiration: 2019-01-20

Abstract

Systems and methods are provided for recycling actinides from molten chloride fuel salts that have been employed as fuel within a molten salt nuclear reactor. The used molten chloride fuel salts can contain soluble fission products (e.g., non-actinide fission products) that contaminate the molten chloride fuel salt mixture, as well as recoverable actinide chlorides. In one aspect, the contaminating non-actinide fission products can be separated from the molten chloride fuel salt mixture. Subsequently, actinide chlorides remaining within the molten fuel salts can be partitioned into a liquid bismuth phase. These actinides can then be re-chlorinated (e.g., oxidized) to strip them out of the liquid bismuth phase and into a clean molten chloride salt mixture that does not contain contaminating non-actinide fission products and that can be pumped back to the nuclear reactor core as fuel.

Description

ACTINIDE RECYCLING SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/364,606, filed July 20, 2016, entitled "Internal Actinide Recycle System," and U.S. Provisional Patent No. 62/365,151, filed July 21, 2016, entitled "Internal Actinide Recycle System." The entirety of each of the above-identified applications is incorporated by reference.

Field

[0002] Embodiments of the disclosure generally relate to molten salt reactors, and specifically relates to processing contaminated molten salt to extract actinides for use as nuclear fuel.

BACKGROUND

[0003] The global demand for energy has largely been fed by fossil fuels. This typically involves taking reduced carbon out of the Earth and burning it. However, those hydrocarbons are in limited supply and burning the hydrocarbons produces carbon dioxide. According to the U.S. Environmental Protection Agency, more than 9 trillion metric tons of carbon is released into the atmosphere each year. Nuclear power is appealing due to possibilities of abundant fuel and carbon-neutral energy production.

[0004] The predominant commercial nuclear reactor for electricity production is the light water reactor (LWR). LWR's have significant drawbacks however. For example, they can use solid fuel with long radioactive half-lives and they can have relatively inefficient fuel utilization. As a result, LWR's can produce dangerous and long-lived waste products. The fuel can also be vulnerable to extreme accidents or proliferation of plutonium to make nuclear weapons.

[0005] To improve on LWR technologies, molten salt reactors (MSRs) have been researched since the 1950s. MSRs are a class of nuclear fission reactors in which the primary coolant, or even the fuel itself, is a molten salt mixture. In general, MSRs can provide energy more safely and cheaply than LWRs. As an example, MSRs are low pressure and can be potentially less expensive and passively safer than LWRs. Furthermore, compared to LWRs, MSRs can provide lower per-kilowatt hour (kWh) levelized cost, comparatively benign fuel and waste inventory composition, and more efficient fuel utilization. [0006] Development of MSRs since the 1970s has taken a back seat, while the United States and other nations focused on the development of LWRs. However, as the world seeks more environmentally friendly, carbon-free energy, and as LWR maintenance and upgrade costs continue to rise, there has been renewed interest in MSRs.

SUMMARY

[0007] Despite their relative advantages over light water reactors (LWRs), the byproducts of fuel salts employed in Molten Salt Reactors (MSRs) still contain fissile materials that can include actinides. These unutilized actinides can be dangerous waste products and they can indicate fuel inefficiency.

[0008] Embodiments of the present disclosure provide systems and methods for recycling actinides from molten chloride fuel salts that have been employed as fuel within a molten salt nuclear reactor. As discussed in greater detail below, the used molten chloride fuel salts can contain soluble fission products (e.g., non-actinide fission products) that contaminate the molten chloride fuel salt mixture, as well as recoverable actinide chlorides. In one aspect, the contaminating non-actinide fission products can be separated from the molten chloride fuel salt mixture. Subsequently, actinide chlorides remaining within the molten fuel salts can be partitioned into a liquid bismuth phase. These actinides can then be re-chlorinated (e.g., oxidized) to strip them out of the liquid bismuth phase and into a clean molten chloride salt mixture that does not contain contaminating non-actinide fission products and that can be pumped back to the nuclear reactor core as fuel.

[0009] Embodiments of the disclosure can allow for increased utilization of nuclear fuel by recycling actinides that would otherwise be discarded as waste along with fission products that must be periodically separated from the fuel salt to maintain its reactivity and physical properties. Accordingly, the disclosed embodiments can also help to generate cleaner nuclear waste, due to removal of high concentrations of long-lived radioactive actinides.

Embodiments of the disclosed recycling system can also reduce fuel costs by requiring less frequent replenishment of high-enriched uranium or plutonium.

[0010] As discussed in greater detail below, embodiments of the disclosure subject actinides contained within a partially burned up molten fuel salt (e.g., a chloride fuel salt) to a two-step process that enables recycling of the actinides. A base salt (e.g., NaCl-CaCl₂, NaCl-KCl, NaCl-CaCl₂-KCl, etc.) can contain non-actinide fission products in the form of chlorides and can be sent to waste processing or storage. Actinides can be returned to the reactor as chlorides (e.g., UCI₃). Embodiments of the present disclosure can enable substantially full utilization of the energy content within these actinides and can minimize the environmental impact from the generation of radioactive waste from the reactor. Examples of quaternary fuel salt compositions (e.g., NaCl-CaCi₂-KCl-UCi₃) are discussed in detail in U.S.

Provisional Application No. 62/434,960, entitled "Salt Compositions for Molten Salt Nuclear Power Reactors," the entirety of which is hereby incorporated by reference.

[0011] Recycling actinides can involve an extraction step followed by a stripping step. In the extraction step, a contaminated molten salt can be introduced to an extraction vessel containing liquid bismuth. A calcium metal anode can be inserted into the molten salt and electrons can be transferred from calcium anode, through a power supply, into the bismuth. Simultaneously, calcium ions can be formed in the salt and actinide ions can be reduced from the salt into the bismuth. The resultant bismuth- actinide solution can be transferred to a stripping vessel, while the resulting salt can be discarded as waste after suitable processing to stabilize it into a waste form.

[0012] Stripping can be performed in a second, stripping vessel that is separate from the extraction vessel. The stripping vessel can be employed to re-chlorinate actinides dissolved in the liquid bismuth and partition them back into a molten salt phase. In one embodiment, the stripping vessel can includes a cathode formed from a porous ceramic or glass membrane loaded with bismuth chloride. The cathode can be immersed in the salt and a current can be passed via a molybdenum rod. The bismuth chloride can reduce to bismuth, releasing chloride ions through the permeable membrane. These chloride ions can subsequently oxidize the actinide ions in the liquid bismuth, partitioning them into a molten salt phase. The resulting clean molten salt product can be recycled to the nuclear reactor core, and the bismuth can be recycled back to the extraction vessel to repeat the process.

[0013] In one embodiment, a method for recycling actinides from a contaminated molten salt mixture is provided and can include providing a contaminated molten salt mixture including a molten salt, one or more actinides, and one or more non-actinide fission products, contacting the contaminated molten salt mixture with liquid bismuth and a calcium metal anode. The method can also include transferring ionic charge from the liquid bismuth through the contaminated molten salt mixture to the calcium anode, thereby reducing the one or more actinides and generating an actinide-bismuth solution. The method can additionally include oxidizing the one or more actinides in the actinide-bismuth solution with chloride ions to produce a molten salt including one or more chlorinated actinides.

[0014] Embodiments of the contaminated molten salt mixture can have a variety of configurations. In one aspect, the contaminated molten salt mixture can be a byproduct from a molten salt reactor core. In another aspect, the contaminated molten salt mixture can include chloride salts such as NaCl, CaCl₂, KC1, UCI₃ in any combination. In a further aspect, aliquots of the contaminated molten salt mixture can be provided at regular time intervals from a nuclear reactor core.

[0015] In an embodiment of the method, calcium ions from the calcium metal anode can be oxidized and dissolved into the contaminated molten salt mixture.

[0016] In an embodiment, the method can further include separating the actinide-bismuth solution from the contaminated molten salt mixture.

[0017] In an embodiment of the method, the oxidizing step can occur in a separate vessel from the transferring step.

[0018] In an embodiment of the method, the oxidizing step can generate actinide-free liquid bismuth.

[0019] In an embodiment of the method, the oxidizing step can include contacting the actinide-bismuth solution with chlorine gas.

[0020] In an embodiment, the method can also include generating the chloride ions by sending electrons through a cathode containing bismuth chloride.

[0021] In one embodiment, a system for recycling actinides from a contaminated molten salt mixture is provided and can include an extraction unit and a stripping unit. The extraction unit can include a first vessel containing a first volume of liquid bismuth and configured to receive a contaminated molten salt mixture including a contaminated molten salt, one or more actinides, and one or more non-actinide fission products. The extraction unit can also include an anode and a first electrochemical cell. The anode can include calcium metal and the anode can be positioned within the first vessel in contact with the contaminated molten salt mixture. The first electrochemical cell can be configured to send electrons from the liquid bismuth through the contaminated salt mixture to the anode for reducing the actinides and generating an actinide-bismuth solution. The stripping unit can include a second vessel, different from the first vessel that contains liquid bismuth and configured to receive the actinide-bismuth solution from the extraction unit. The stripping unit can also include a cathode and a second electrochemical cell. The cathode can include bismuth chloride and a wall permeable to chloride ions. The second electrochemical cell can be configured to send electrons through the cathode to reduce the bismuth chloride and to release chloride ions into the actinide-bismuth solution to generate chlorinated actinides.

[0022] In an embodiment, the contaminated molten salt mixture can be a byproduct from a molten salt reactor core.

[0023] In an embodiment, the first and second volumes of liquid bismuth can be at a temperature selected from the range between about 600°C and about 800°C.

[0024] The contaminated molten salt mixture can include chloride salts, such as NaCl,CaCl₂, KC1, UCI₃ in any combination.

[0025] In an embodiment, calcium ions from the calcium metal anode can be oxidized and dissolved into the contaminated molten salt mixture.

[0026] In an embodiment, the wall of the cathode can be formed from a ceramic.

[0027] In an embodiment, generating chlorinated actinides can leaves behind actinide-free liquid bismuth. The actinide-free liquid bismuth can pumped back to the extraction vessel to be reused.

[0028] In an embodiment, the extraction unit can include a reference electrode made of mullite.

[0029] In an embodiment, the reference electrode can contain silver chloride.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] These and other features will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0031] FIG. 1 shows a flowchart illustrating one embodiment of an actinide recycling system connected to a molten salt reactor. [0032] FIG. 2 shows one embodiment of a cathode for use with a stripping unit of the actinide recycling system of FIG. 1.

[0033] FIG. 3 shows a diagram of one embodiment of a method for recycling actinides in accordance with the present disclosure.

[0034] It is noted that the drawings are not necessarily to scale. The drawings are intended to depict only typical aspects of the subject matter disclosed herein, and therefore should not be considered as limiting the scope of the disclosure.

DETAILED DESCRIPTION

[0035] Embodiments of the present disclosure provide systems and methods for recycling actinides in a molten salt reactor (MSR) to increase fuel efficiency and reduce harmful nuclear waste.

[0036] MSRs are a class of nuclear fission reactors in which the primary coolant, or even the fuel itself, is a molten salt mixture (e.g., fluoride or chloride salt). Compared to the more common light water reactors (LWRs), MSRs according to embodiments of the present disclosure can offer projected lower per-kilowatt hour (kWh) levelized cost, comparatively benign fuel and waste inventory composition, highly efficient fuel utilization, longer reactor lifetime, lower amenability to fissile material proliferation, and a combination of higher accident resistance with lower worst-case accident severity (due to more benign inventory composition). In various designs, the innate physical properties of MSRs can prohibit uncontrolled fuel heating.

[0037] Persistent challenges in the design of MSR are to increase nuclear fuel efficiency and to reduce dangerous actinide waste. Embodiments of the present disclosure can address these challenges by extracting actinides from contaminated molten salt(s) and transferring these actinides into clean molten salt(s) that can be pumped back to the reactor core. Further embodiments provide for in-situ processing to separate and recycle components in order to maximize efficiency and minimize waste production. Disclosed embodiments can also address the need to selectively recycle actinides from molten salt(s) having accumulated concentrations of soluble fission products and therefore in condition for waste processing and/or disposal. [0038] In one embodiment, non-actinide fission products can be separated from a contaminated molten chloride salt mixture to generate a first clean molten chloride salt mixture. In a further embodiment, actinides contained within contaminated molten fuel salts can be partitioned into a liquid bismuth phase and then subsequently re-chlorinated to strip these actinides from the liquid bismuth phase into a second clean molten chloride salt mixture. The second clean molten chloride salt can be subsequently pumped back to a nuclear reactor core as fuel.

[0039] Embodiments of the disclosed systems and methods can also provide increased utilization of nuclear fuel by recycling actinides that would otherwise be discarded as waste. Cleaner nuclear waste can result, as high concentrations of long-lived radioactive actinides can be removed from waste fuel salt. Embodiments of disclosed actinide recycling systems can also reduce the cost of fuel for operating MSRs by requiring less frequent replenishment of high-enriched uranium or plutonium.

[0040] Embodiments of the disclosure can subject actinides contained within a partially burned up molten chloride fuel salt to a two-step process to enable their recycling of the actinides into clean molten chloride salts. A base salt (e.g., NaCl-CaCl₂, NaCl-KCl, NaCl- CaCl₂-KCl) that contains non-actinide fission products in the form of chlorides can be sent to waste processing or storage. The actinides can be returned to the reactor as chlorides. Thus, increased utilization of the energy content within these actinides can be achieved while environmental impact from the generation of radioactive waste from the reactor can be minimized.

[0041] Embodiments of the disclosed systems and methods can be employed in conjunction with an MSR. The MSR can periodically or continuously pump contaminated molten salts to an external recycling system of the present disclosure for treatment and disposal of the waste.

[0042] FIG. 1 shows a diagram of an embodiment of a recycling system 100 for recycling actinides from an MSR salt. The recycling system 100 can be connected to a nuclear reactor core 220 (e.g., an MSR reactor core). The nuclear reactor core 220 can pump molten, contaminated salt 133 to an extraction unit 130. After electrochemical transfer of actinides from the contaminated salt 133 into a liquid bismuth pool 137, the resulting salt can be pumped to a waste process 180 and the bismuth can be pumped to a stripping unit 150. [0043] In the stripping unit 150, the actinides can be electrochemically transferred from the bismuth phase (e.g., bismuth pool 157 containing actinides extracted from the contaminated salt 133) to another pool or layer of molten salt 153. The salt layer 153 can initially include a chloride salt (e.g., NaCl-CaCl₂, NaCl-KCl, NaCl-CaCl₂-KCl) that is substantially free of other components. The bismuth pool 157 can be depleted of actinides in the stripping unit 150. Subsequently, the depleted bismuth can be pumped back to the extraction unit 130; allowing the depleted bismuth to serve as the bismuth pool 137 in a subsequent extraction cycle on a new batch of contaminated salt 133 from the reactor core 220.

[0044] The extraction unit 130 can include an extraction vessel 131. The extraction vessel 131 can be cylindrical and it can be made of a material that is compatible with molten chloride salt and liquid bismuth. The extraction vessel 131 can initially contain a bismuth pool 137 at a temperature selected within the range from about 600°C to about 800°C. The extraction vessel 131 can also include the contaminated salt 133 removed (e.g., pumped) from the reactor core 220. In the extraction vessel 131, the contaminated salt 133 can be positioned above the level of the bismuth pool 137.

[0045] The contaminated salt 133 can be transferred from the reactor core 220 to the extraction unit 130 continuously or in batches during the operation of the reactor core 220. If operated in a batch mode, a fixed volume of contaminated salt 133 (e.g., about 1 liter, about 10 liters, about 100 liters, about 1000 liters, etc.) can be removed from the reactor core 220 and be sent to the recycling system 100. In one embodiment, the contaminated salt 133 can be removed from the reactor core 220 at pre-specified time intervals so that regular batches can be sent to the recycling system 100. In another embodiment, a batch of contaminated salt 133 can be sent upon the triggering of a pre-selected event, such as a signal from a monitoring system that measures the composition of the contaminated salt 133 within the reactor core 220.

[0046] The extraction unit 130 can also include a solid cylindrical anode 139. In an embodiment, the anode 139 can be made of calcium metal. When the contaminated salt 133 has been transferred into the extraction vessel 131, the anode 139 can be partially submerged in the contaminated salt 133. The liquid bismuth within the bismuth pool 137 can be denser than the contaminated salt 133, and so the contaminated salt 133 can be positioned above the bismuth pool 137. As shown in the embodiment of FIG. 1, the calcium anode 139 can be positioned out of direct contact with the bismuth pool 137 within the extraction unit 130. This arrangement can allow charge to flow through the contaminated salt 133 as ions to a cathode, as described below. Optionally, a reference electrode can include a mullite tube containing a chloride salt mixture with silver chloride and a silver wire lead also inserted into the contaminated salt 133. The reference electrode can provide superior control over the process to maintain efficient and proper operation.

[0047] The wall of the extraction vessel 131 can be connected to an electrochemical cell 138 to serve as the cathode. The combination of the wall of the extraction vessel 131 and the bismuth pool 157 can effectively become the cathode. An electric current can be passed through the electrochemical cell 138, sending electrons from the bismuth pool 137 to the contaminated salt 133 and then from the contaminated salt 133 into the anode 139. The cathode's potential can be maintained at a level designed to selectively reduce actinides from the contaminated salt 133 into a solution with the liquid bismuth within the bismuth pool 137.

[0048] Meanwhile, calcium ions from the anode 139 can be oxidized and partitioned into the contaminated salt 133. As the actinide ions partition into the bismuth pool 137, they can be effectively replaced in the contaminated salt 133 by the calcium ions oxidized from the anode 139.

[0049] The anode 139 can be a sacrificial anode. The anode 139 is referred to as sacrificial because its calcium ions can be oxidized in the extraction process occurring within the extraction unit 130. The use of a sacrificial anode 139 can be advantageous over designs that use an inert anode (e.g., one that requires chlorine gas to be generated to provide the chlorine ions). Chlorine gas can be difficult to handle and control, and it can cause corrosion of structural materials at high temperature.

[0050] Using the anode 139 as a sacrificial anode can also be advantageous for keeping the volume of contaminated salt 133 relatively constant during the extraction process. For the nominal composition of the contaminated salt 133 coming out of the reactor core 220, the recycling system 100 can maintain conditions that prevent the contaminated salt 133 from freezing during the extraction process. As an example, pressure and temperature conditions can be controlled based on the respective amounts of chloride salts (e.g., NaCl, CaCl₂, KC1, UCI₃, etc.) within the contaminated salt 133 to keep it in the liquid (molten) phase. [0051] In an embodiment of the present disclosure where the contaminated salt includes NaCl, CaCl₂, and UCI₃, UCI₃ can be replaced by CaCl₂ from the anode 139 in order to keep the volume of the contaminated salt 133 relatively constant. It can also prevent the NaCl concentration from becoming too high which can lead to freezing of the salt. Essentially, by replacing UCI₃ with CaCl₂, the composition of the contaminated salt 133 can be bracketed in such a way as to keep its melting point well below the operating temperature of the reactor core 220. In contrast, if an inert anode were employed rather than the sacrificial anode 139, loss of UCI₃ from the contaminated salt 133 could result in a dramatic decrease in volume of the contaminated salt 133, which can complicate the electrochemical extraction process.

[0052] The extraction process can be performed for a length of time such as 10-15 hours. This time period can be pre-determined or based upon a concentration of actinides remaining in the contaminated salt 133. As an example, the extraction process can continue until a desired amount of actinides (e.g., about 95%) have partitioned from the contaminated salt 133 into the bismuth pool 157.

[0053] In some embodiments, the current can be occasionally turned off and an open circuit potential between the bismuth pool 137 and the reference electrode can be measured to evaluate the concentration of actinides remaining in the contaminated salt 133. The extraction process can proceed until a user-established degree of actinide separation has been achieved.

[0054] As shown in FIG. 1, salt resulting from the extraction process (FP salt) can be sent to a salt waste process 180 for immobilization, while the actinide loaded bismuth can be pumped to from the extraction unit 130 the stripping unit 150 (Bi/U/TRU).

[0055] The stripping unit 150 can include a stripping vessel 151 that can be cylindrical and it can be made of a material that is compatible with molten chloride salt and liquid bismuth. The stripping vessel 151 can be operated at a temperature within the range between about 600°C to about 800°C. The stripping unit 150 can operate to re-chlorinate (oxidize) actinides dissolved in the liquid bismuth phase (bismuth pool 157) and partition them back into a salt layer 153. In an embodiment, the salt layer can be composed initially only of NaCl-CaCl₂. In an alternative embodiment, the salt layer can be composed initially only of NaCl-KCl. In a further alternative embodiment, the salt layer can be composed initially only of NaCl-CaCl₂- KC1. [0056] There are two different ways to operate the stripping unit 150 to provide chloride ions. In a first embodiment, the stripping unit 150 can include a permeable cathode 200 containing bismuth chloride. When a current is passed through the cathode 200 (e.g., from an electrochemical cell 158), chloride ions can be released into the electrolyte (e.g., the salt layer 153). In a second embodiment, chlorine (CI₂) gas can be bubbled into the bismuth pool 157 to provide the chloride ions.

[0057] An embodiment of the cathode 200 in accordance with this first embodiment is shown in FIG. 2. The design of the cathode 200 can effectively supply the chloride ions needed for partitioning the actinides back into the salt layer 153 from the bismuth pool 157 by driving the oxidation of actinide ions electrochemically. The cathode 200 can include a porous wall or membrane 205. The wall 205 can be made of any compatible material such as ceramic or glass, which can allow chloride ions to pass through. The cathode 200 can initially be loaded with bismuth chloride (B1CI₃) and it can be immersed in the salt layer 153 of the stripping unit 150. As current is passed through the cathode 200, the B1CI₃ can be reduced to bismuth metal, releasing chloride ions into salt layer 153. These chloride ions can join with actinide ions at the surface of the bismuth pool 157 (which in this case is an anode) to oxidize the actinide ions.

[0058] Alternatively, in the second embodiment, CI₂ gas can be bubbled directly into the bismuth pool 157 containing actinides using a CI₂ gas bubbling system (not shown). As a result, the actinides can be oxidized to chlorides which can then partition into the salt layer 153.

[0059] The first embodiment, which utilizes the cathode 200 with B1CI₃, can minimize corrosion arising from direct chlorination of the actinides using CI₂ gas. However, in the second embodiment, chlorine gas supplied to the bismuth pool 157 can be controlled to substantially prevent corrosion of the wall of the stripping vessel 151 and to prevent conversion of UCI₃ to UCI₄. In an embodiment, the CI₂ gas bubbling system can leave a selected portion of the actinides in the bismuth pool 157, rather than partitioning all of them into the salt layer 153. This design can help to prevent corrosion and conversion of UCI₃ to UCI4.

[0060] In either embodiment, after a desired amount of actinides have been oxidized and partitioned out of the bismuth pool 157, the salt layer 153 can be separated from the bismuth pool 157. The salt layer 153 can be pumped back to the reactor core 220 to be burned as fuel. The bismuth pool 157 depleted of actinides can then be pumped back to the extraction unit 130. In this manner, liquid bismuth can be repeatedly transferred back and forth between the extraction unit 130 and the stripping unit 150.

[0061] The extraction process can be a single stage operation, requiring only one extraction unit 130 and one stripping unit 150, as shown in the recycling system 100 of FIG. 1. An effective single-stage design can be possible due to the high efficiency of electrochemical separation. In some embodiments, up to 95% or more of the actinides can be recycled with a single stage operation. The recycling system 100 can therefore be less costly than extraction systems requiring multiple stages.

[0062] In other embodiments, where a higher efficiency is needed (e.g., removal of greater than about 95% of the actinides), additional stages can be added, so that additional extraction and stripping stages occur in series.

[0063] In certain embodiments, a portion of the contaminated salt 133 extracted from the reactor core 220 can be diverted from delivery to the extraction unit and can instead be directed (arrow 170) to merge with the flow of clean molten chloride fuel salt from the stripper unit 150 to the reactor core 220. This diversion can reintroduce contaminants into flow of clean molten chloride fuel salt, which can allow the level of contaminants (e.g., soluble, non-actinide fission products) returning to the reactor 202 to be tailored (e.g., for discouraging proliferation of nuclear fuel). One skilled in the art will appreciate that the diversion of contaminated salt 133 represented by arrow 170 is one exemplary embodiment and that the contaminated salt 133 can be diverted to merge with the flow of clean molten chloride fuel salt from the stripper unit 150 to the reactor core 220 at other locations.

[0064] FIG. 3 is a flow diagram illustrating one exemplary embodiment of a method 301 for recycling actinides from a contaminated molten salt mixture. The salt mixture can be a contaminated salt (e.g., contaminated salt 133) and the method 301 can be performed with the recycling system 100 discussed above. The method 301 can include providing the contaminated molten salt mixture in operation 309. The contaminated molten salt mixture can include, but is not limited to, one or more molten salts, one or more actinides, and one or more non-actinide fission products. The one or more molten salts can be provided from a reactor core of an MSR (e.g., reactor core 220). [0065] In operation 315, the contaminated molten salt mixture can be contacted with liquid bismuth and a calcium metal anode. The contacting operation 315 can occur in an extraction vessel (e.g., extraction vessel 131) as described above.

[0066] In operation 321, electrons can be transferred from the liquid bismuth to the calcium anode through the contaminated molten salt mixture. In this manner, actinides dissolved in the liquid bismuth can be reduced, and generating an actinide -bismuth solution.

[0067] In operation 327, the actinides in the actinide-bismuth solution can be oxidized with chloride ions and combined with a molten salt (e.g., salt layer 153) to produce a molten salt including chlorinated actinides.

Incorporation by Reference

[0068] Any and all references and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web content, that have been made throughout this disclosure are hereby incorporated herein by reference in their entirety for all purposes.

Equivalents

[0069] Embodiments of the present disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the foregoing embodiments can therefore be considered in all respects illustrative rather than limiting on the subject matter described herein.

Claims

What is claimed is:

1. A method for recycling actinides from a contaminated molten salt mixture, the method comprising:

providing a contaminated molten salt mixture comprising a molten salt, one or more actinides, and one or more non-actinide fission products;

contacting the contaminated molten salt mixture with liquid bismuth and a calcium metal anode;

transferring ionic charge from the liquid bismuth through the contaminated molten salt mixture to the calcium metal anode, thereby reducing the one or more actinides and generating an actinide-bismuth solution; and

oxidizing the one or more actinides in the actinide-bismuth solution with chloride ions to produce a molten salt comprising one or more chlorinated actinides.

2. The method of claim 1, wherein the contaminated molten salt mixture is a byproduct from a molten salt reactor core.

3. The method of claim 1, wherein the contaminated molten salt mixture comprises NaCl-CaCl₂, or NaCl-KCl, or NaCl-CaCl₂-KCl.

4. The method of claim 1, wherein aliquots of the contaminated molten salt mixture are provided at regular time intervals.

5. The method of claim 1, wherein calcium ions from the calcium metal anode are oxidized and dissolved into the contaminated molten salt mixture.

6. The method of claim 1, further comprising separating the actinide-bismuth solution from the contaminated molten salt mixture.

7. The method of claim 1, wherein the oxidizing step occurs in a separate vessel from the transferring step.

8. The method of claim 1, wherein the oxidizing step generates actinide-free liquid bismuth.

9. The method of claim 1, wherein the oxidizing step comprises contacting the actinide- bismuth solution with chlorine gas.

10. The method of claim 1, further comprising generating the chloride ions by sending electrons through a cathode containing bismuth chloride.

11. A system for recycling actinides from a contaminated molten salt mixture, the system comprising:

an extraction unit comprising:

a first vessel containing a first volume of liquid bismuth and configured to receive a contaminated molten salt mixture comprising molten salt, one or more actinides, and one or more non-actinide fission products;

an anode comprising calcium metal, the anode positioned within the first vessel in contact with the contaminated molten salt mixture;

a first electrochemical cell configured to send electrons from the first volume of liquid bismuth through the contaminated molten salt mixture to the anode for reducing the actinides and generating an actinide-bismuth solution; and

a stripping unit comprising:

a second vessel, different than the first vessel, containing a second volume of liquid bismuth and configured to receive the actinide-bismuth solution from the extraction unit;

a cathode comprising bismuth chloride and a wall permeable to chloride ions; and

a second electrochemical cell configured to send electrons through the cathode to reduce the bismuth chloride and release chloride ions into the actinide-bismuth solution to generate chlorinated actinides.

12. The system of claim 11, wherein the contaminated molten salt mixture is a byproduct from a molten salt reactor core.

13. The system of claim 11, wherein the first and second volumes of liquid bismuth are at a temperature selected from the range between about 600°C to about 800°C.

14. The system of claim 11, wherein the contaminated molten salt mixture comprises NaCl-CaCl₂, or NaCl-KCl, or NaCl-CaCl₂-KCl.

15. The system of claim 11, wherein calcium ions from the calcium metal anode are oxidized and dissolved into the contaminated molten salt mixture.

16. The system of claim 11, wherein the wall of the cathode is formed from a ceramic.

17. The system of claim 11, wherein generating chlorinated actinides leaves behind an actinide-free liquid bismuth and wherein the actinide-free liquid bismuth is pumped back to the extraction vessel to be reused.

18. The system of claim 11, further comprising a reference electrode comprising mullite.

The system of claim 18, wherein the reference electrode contains silver chloride.