WO2018064572A1

WO2018064572A1 - Silver chloride waste form and apparatus

Info

Publication number: WO2018064572A1
Application number: PCT/US2017/054496
Authority: WO
Inventors: Darryl SIEMER
Original assignee: Elysium Industries Ltd
Current assignee: Elysium Industries Ltd
Priority date: 2016-09-29
Filing date: 2017-09-29
Publication date: 2018-04-05
Anticipated expiration: 2019-03-29

Abstract

System and methods for disposing of waste from a fluid-fueled reactor are provided. A method can include mixing a waste salt from a fluid-fueled reactor with silver chloride (AgCl) and powdered silver to form a waste mixture, sealing the waste mixture within a chamber, evacuating air around the waste mixture from the chamber, and treating the chamber.

Description

SILVER CHLORIDE WASTE FORM AND APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/401,458, filed September 29, 2016, entitled "Silver Chloride Waste Form and Apparatus," the entirety of which is incorporated by reference.

BACKGROUND

[0002] 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 can produce carbon dioxide. According to the U.S. Environmental Protection Agency, more than 9 trillion metric tons of carbon are released into the atmosphere each year. Nuclear power is an appealing alternative to fossil fuels due to relative abundance of nuclear fuel and carbon-neutral energy production.

[0003] Light water reactors (LWRs) are the predominant commercial nuclear reactor for electricity production. LWRs have significant drawbacks, however. In one example LWRs can use solid fuels that have long radioactive half-lives. In another example, LWRs can utilize fuels in a relatively inefficient manner. As a result, LWRs can produce dangerous and long-lived waste products. Nuclear fuel can also be vulnerable to extreme accidents or proliferation (e.g., plutonium) to make nuclear weapons.

[0004] Molten salt reactors (MSRs) have been researched since the 1950s to improve on LWR technologies. MSRs are a class of nuclear fission reactors in which the primary coolant, or even the fuel itself, can be a molten salt mixture. In general, MSRs can provide energy more safely and cheaply than LWRs. As an example, MSRs can operate at relatively low pressures and they can be potentially less expensive and passively safer than LWRs. Furthermore, compared to LWRs, MSRs can also provide advantages such as lower levelized cost on a per-kilowatt hour (kWh) basis, fuel and waste inventories of relatively benign composition, and more efficient fuel utilization.

[0005] Based on projected population growth, currently deployed energy technologies are not considered sufficient to meet rising energy demands of developed countries, let alone undeveloped and developing countries. MSRs represent a technology that can fill this gap. Unfortunately, since the 1970s, the United States and other nations have focused on development of LWRs instead of MSRs.

[0006] Interest in development of MSRs has steadily increased within recent years, however, given their advantages over LWRs. In aspect, the cost to maintain and upgrade LWR facilities continue to rise and storage of nuclear waste remains a contentious public policy issue. In another aspect, due to security threats posed by terrorists, many nations and global organizations have increased resources directed to prevent proliferation of nuclear materials.

SUMMARY

[0007] Embodiments of the disclosure relate to processing waste fuel salt from a liquid fueled reactor (e.g., a fast-spectrum-molten-salt reactor (FSMSR)).for disposal. The radiation emitted by waste fuel salt can produce radiolysis products including combustible and corrosive gasses. If radiolysis continues unchecked, the activity of the stored waste fuel can become unpredictable and even catastrophic. It can be desirable to account for and help to mitigate the risks associated with stored waste salt from a liquid fueled reactor, as this waste can be stored in remote locations for years.

[0008] An FSMSR system, also sometimes referred to as a "fast neutron reactor" or simply a "fast reactor," can generally include a category of a nuclear reactor in which the fission chain reaction is sustained by fast neutrons, as opposed to slow, or thermal, neutrons used in a thermal reactor. The term "thermal" refers to thermal equilibrium with the medium it is interacting with, the reactor' s fuel, moderator and structure, which is much lower energy than the fast neutrons initially produced by fission. Thermal reactors can rely on a neutron moderator for reducing the speed of neutrons so as to make them capable of sustaining a nuclear chain reaction. The moderator can slow neutrons until they approach the average kinetic energy of the surrounding particles (e.g., reducing the speed of the neutrons to low- velocity thermal neutrons), thereby remaining uncharged and allowing them to penetrate deeper in the target element and close to the nuclei. Fast reactors, however, do not require a neutron moderator, but must rather use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor.

[0009] The systems, devices, and methods described throughout this disclosure are compatible with a variety of liquid fueled reactors, including those fueled by a chloride salt. By adding stabilization salts (e.g., AgCl) and chlorine scavengers (e.g., powdered silver) to the waste fuel salt before storage, the potential chlorine radiolysis is addressed. By extension, the UC1₆ mobilization potential is also addressed. In addition, the disposing or storing the waste fuel salt in a manner consistent with embodiments of the present disclosure can relatively easy and cost effective.

[0010] In one embodiment, a method of disposing of waste from a fluid-fueled reactor is provided. The method can include mixing a waste salt from a fluid-fueled reactor with silver chloride (AgCl) and with powdered silver (Ag) to form a waste mixture. The method can also include sealing the waste mixture within a chamber, evacuating air around the waste mixture from the chamber, and treating the chamber after sealing the waste mixture therein.

[0011] In another embodiment, treating the chamber can include positioning the chamber within a hot isostatic press (HIP) and pumping an inert gas into the HIP, the inert gas exerting a pressure selected from about 500 psi to about 20,000 psi on the chamber. The method can also include, while the chamber is under pressure, raising the temperature within the HIP to a level selected from the range of about 500°F to about 3,000 °F for a time sufficient to reduce voids within a microstructure of the chamber.

[0012] In another embodiment, the method can include at least partially forming the chamber around the waste mixture. As an example, the method can include welding an open end of a copper tube to form a first sealed end. The method can also include adding the waste mixture to the copper tube through the open end. The method can also include evacuating air from the copper tube. The method can also include welding the open end of the copper tube to form a second sealed end to thereby sealing the waste mixture between the sealed ends.

[0013] In another embodiment, the method can include, after treatment, disposing of the chamber including the waste mixture sealed therein. As an example, disposing of the chamber including the waste mixture can include burying the chamber.

[0014] In another embodiment, the waste mixture can be allowed to settle within the chamber before evacuating the air.

[0015] In another embodiment, the mixing can include grinding the waste salt with the AgCl. [0016] In another embodiment, the chamber can be formed from a copper material. As an example, the chamber can be formed from a copper tube. The chamber can have a wall thickness of less than about 10 cm.

[0017] In another embodiment, the method can include separating the chamber from excess material beyond the sealed ends.

[0018] In another embodiment, the waste mixture can include a ratio of waste salt to AgCl of about 1:5.

[0019] In another embodiment, the waste mixture can include about 2 wt.% powdered silver.

[0020] In another embodiment, the treatment can include consolidating the waste mixture. Consolidation of the waste mixture can include compressing the chamber from a first height to a second height. As an example, the second height can be less than about 99% of the first height.

[0021] In another embodiment, waste salt can include actinides and fission products.

[0022] In a further embodiment, a waste disposal system for a fluid-fueled reactor is provided and it can include a chamber and a hot isostatic press (HIP). The chamber can enclose a waste mixture including waste salt from a fluid-fueled reactor, silver chloride (AgCl), and powdered silver. The HIP can be configured to reduce voids within a microstructure of the chamber.

[0023] In another embodiment, the HIP can include a vessel and at least one heater. The vessel can be connected to a gas source via a gas conduit. The at least one heater can be positioned within the vessel. The HIP can be configured to exert a pressure a pressure selected from the range of about 500 psi to about 20,000 psi on the vessel.

[0024] In another embodiment, the chamber can be formed from a copper material. As an example, the chamber can be formed from a copper tube.

[0025] In another embodiment, the waste mixture can include about 2 wt. % powdered silver. [0026] In another embodiment, the waste salt can include actinides and fission products. [0027] In another embodiment, a reactor system is provided. The reactor system can include a reactor and a waste disposal assembly. The reactor can include a reactor vessel, a neutron reflector, a heat exchanger, and a pump. The neutron reflector can be positioned within the reactor vessel to at least partially form one or more channels within the reactor vessel. The heat exchanger can be connected to at least one of the channels. The pump can be configured to circulate a fuel salt through the reactor vessel via at least one of the channels. The waste disposal assembly can be in fluid communication with the reactor vessel and it can be configured to receive, from the reactor vessel, a waste salt extracted from the fuel salt. The waste disposal assembly can include a chamber and a hot isostatic press (HIP). The chamber can be configured to receive a waste mixture including the waste salt, silver chloride (AgCl), and powdered silver. The HIP can be configured to reduce voids within a microstructure of the chamber.

[0028] These and other aspects, features, and implementations, and combinations of them, may be expressed as apparatus, methods, methods of doing business, means or steps for performing functions, components, systems, program products, and in other ways.

[0029] Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

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 is a schematic illustration of one exemplary embodiment of a nuclear thermal generating plant (NTGP).

[0032] FIG. 2 is a schematic diagram depicting a fuel conditioning system of the NTGP of FIG. 1 in greater detail.

[0033] FIG. 3 schematically illustrates a cross section of components of a salt waste disposal system that can be used to dispose of the salt waste produced by the reactors of FIG. 1-FIG. 8. The processed salt waste container is also shown.

[0034] FIG. 4 is a flow diagram illustrating one exemplary embodiment of a method for waste disposal suitable for use with the system of FIG. 1. [0035] FIG. 5 is a flow diagram illustrating one exemplary embodiment of a method for treating a chamber containing the waste.

[0036] FIG. 6 is a flow diagram illustrating one exemplary embodiment of a method for forming a chamber that contains the waste.

[0037] For a thorough understanding of the present disclosure, reference should be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure can be described in connection with exemplary embodiments, the disclosure can be not intended to be limited to the specific forms set forth herein. It can be understood that various omissions and substitutions of equivalents can be contemplated as circumstances can suggest or render expedient.

DETAILED DESCRIPTION

[0038] Successful disposal of waste from a liquid fueled reactor (e.g., a fast-spectrum- molten-salt reactor (FMSR)) can include safely collecting, containing, and storing or disposing of waste fuel

salt. A waste fuel salt from an FMSR system powered by a chloride based fuel salt can include actinides and an accumulated concentration of fission products including non-actinide fission products (e.g., in the form of chlorides).

[0039] FIG. 1 schematically illustrates a nuclear thermal generator plant (NTGP) system 100, which can include a molten salt nuclear reactor configured to use a molten fuel salt or a fuel salt constituent (collectively referred to herein as fuel salt composition) to generate electrical energy from nuclear fission. As shown, the system 100 includes a reactor system 102 and a secondary system 104. The reactor system 102 includes a primary heat exchanger 106 connected to a reactor 110 having a reactor core 112 containing a fuel salt composition 114. The reactor system 102 also includes a reactivity control system 116 and a fuel conditioning system 120, each connected to the reactor 110.

[0040] Embodiments of the fuel salt composition 114 can include fissile materials, fertile materials, and combinations thereof. As an example, components of the fuel salt composition 114 can be in the form of one or more chloride salts, fluoride salts, and mixtures of one or more chloride and fluoride salts. In embodiments where the fuel salt composition 114 includes one or more chloride salts, the system 100 can be referred to as a molten chloride fast reactor (MCFR).

[0041] Examples of fissile materials can include, but are not limited to, thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), and any combination thereof. In certain embodiments, the fissile materials can include one or more of the following isotopes, in any combination: Th-225, Th-227, Th-229, Pa- 228, Pa-230, Pa-232, U-231, U-233, U-235, Np-234, Np-236, Np-238, Pu-237, Pu-239, Pu-241, Am-240, Am-242, Am-244, Cm-243, Cm-245, and Cm-247. Examples of fertile materials can include, but are not limited to, ²³²ThCl₄, ²³⁸UCl₃ and ²³⁸UC1₄. In an embodiment, the fuel salt composition 114 can include a mixture of fissile materials including one or more of ²³³UC1₃, ²³⁵UC1₃, ²³³UC1₄, ²³⁵UC1₄, and ²³⁹PuCl₃; and carrier salts including one or more of sodium chloride (NaCl), potassium chloride (KC1), and calcium chloride (CaC^).

[0042] In certain embodiments, the fuel salt composition 114 can include a carrier salt and a fuel salt. The carrier salt can include a chloride salt of an alkali or alkaline earth metal and the fuel salt can include a chloride salt of at least one actinide. The alkali or alkaline chloride fuel salt can have a concentration selected from about 1 mole % to about 90 mole % of the fuel salt composition 114. In further embodiments, the fuel salt composition 114 can have a melting temperature that is greater than or equal to about 300°C. In additional embodiments, the melting temperature of the fuel salt composition can be selected from about 325°C to about 475°C. In additional embodiments, the fuel salt composition 114 can include less than 20 wt.% of a fissile material (e.g., low-enriched uranium or LEU, U-235) prior to use of the fuel salt composition 114 within the reactor system 102 to perform nuclear fission

[0043] Further embodiments of fuel salt compositions suitable for use with the system 100 are discussed in greater detail in U.S. Provisional Patent Application No. 62/340,754, filed on May 24, 2016, entitled "Chloride and Fluoride Salt Composition For Molten Salt

Reactor," U.S. Provisional Application No. 62/340,762 filed on May 24, 2016, entitled "Salt Composition With Phase Modifiers For Molten Salt Reactor," U.S. Provisional Application No. 62/269,525, filed on December 18, 2015, entitled "Salt Composition for Molten Salt Reactor," and U.S. Application No. 15/380,473, filed on December 15, 2016, entitled "Salt Compositions for Molten Salt Reactors," each of which is hereby incorporated by reference in its entirety. [0044] Upon absorbing neutrons, nuclear fission can be initiated and sustained in the fuel salt composition 114 by chain-reaction within the reactor 1, generating heat that elevates the temperature of the fuel salt composition 114 (e.g., to about 650°C or about 1,200°F). The heated fuel salt composition 114 can be transported from the reactor core 112 to the primary heat exchanger 106 via a primary fluid loop 122 via a pump, discussed in greater detail below. The primary heat exchanger 106 can be configured to transfer heat generated by nuclear fission occurring in the fuel salt composition 114.

[0045] The primary heat exchanger 106 can be provided in a variety of configurations. In various embodiments, the primary heat exchanger 106 can be either internal or external to a reactor vessel (not shown) that contains the reactor core 112. In additional embodiments, the system 100 can be configured such that primary heat exchange (e.g., heat exchange from the molten fuel salt composition 114 to a different fluid) can occur both internally and externally to the reactor vessel. In other embodiments, the system 100 can be provided such that the functions of nuclear fission and primary heat exchange can be integral to the reactor core 112. That is, heat exchange fluids can be passed through the reactor core 112.

[0046] In general, fluids of three types can be contained in and/or circulated through the system 100, namely fuel, coolant, and moderator (e.g., any substance that slows neutrons). Various fluids can perform one or more of the fuel, coolant, and moderator functions simultaneously. One or more fluids, including more than one fluid of each functional type, can be contained within or circulated through the reactor core 112. Examples of fluids contained within or circulated through the reactor core 112 can include, but are not limited to, liquid metals, molten salts, supercritical H₂O, supercritical CO₂, and supercritical N₂O.

[0047] The transfer of heat from the fuel salt composition 114 can be realized in various ways. For example, the primary heat exchanger 106 can include a pipe 124 and a secondary fluid 126. The molten fuel salt composition 114 can travel through the pipe 124, while the secondary fluid 126 (e.g., a coolant) can surrounds the pipe 124 and absorb heat from the fuel salt composition 114. Upon heat transfer, the temperature of the fuel salt composition 114 in the primary heat exchanger 106 can be reduced and fuel salt composition 114 can be subsequently transported from the primary heat exchanger 106 back to the reactor core 112.

[0048] The secondary system 104 can also include a secondary heat exchanger 130 configured to transfer heat from the secondary fluid 126 to a tertiary fluid 132 (e.g., water). As shown in FIG. 1, the secondary fluid 126 is received from primary heat exchanger 106 via fluid loop 134 and circulated through secondary heat exchanger 130 via a pipe 136.

[0049] Additionally or alternatively, in another embodiment (not shown), heat exchange can occur within the reactor core prior to heat exchange within the secondary heat exchanger. As an example, heat from the fuel salt composition can pass to a solid moderator, then to a liquid coolant circulating through the reactor system. Subsequently, the liquid coolant circulating through the reactor system can be transported to the secondary heat exchanger. As required by basic thermodynamics, after one or more stages of exchange, heat can be finally delivered to an ultimate heat sink, e.g., the overall environment (not shown).

[0050] Heat received from the fuel salt composition 114 can be used to generate power (e.g., electric power) using any suitable technology. For example, when the tertiary fluid 132 in the secondary heat exchanger 130 is water, it can be heated to a steam and transported to a turbine 140 by a fluid loop 142. The turbine 140 can be turned by the steam and drive an electrical generator 144 to produce electricity. Steam from the turbine 140 can be conditioned by an ancillary gear 148 (e.g., a compressor, a heat sink, a pre-cooler, and a recuperator) and it can be transported back to the secondary heat exchanger 130 through the fluid loop 142.

[0051] Additionally, or alternatively, the heat received from the fuel salt composition 114 can be used in other applications such as nuclear propulsion (e.g., marine propulsion), desalination, domestic or industrial heating, hydrogen production, or combinations thereof.

[0052] In certain embodiments (not shown), the reactor system can also include an actively cooled freeze plug. The freeze plug can be in fluid communication with the molten salt reactor core and it can be configured to allow the molten fuel salt to flow into a set of emergency dump tanks in case of power failure and/or on active command.

[0053] During the operation of the system 100 to generate power, fission products can be generated in the fuel salt composition 114. In general, the fission products can be radioactive noble metals and/or radioactive noble gases. Non-limiting embodiments of fission products can include, but are not limited to, one or more of the following, in any combination:

rubidium (Rb), strontium (Sr), cesium (Cs), barium (Ba), lanthanides, palladium (Pd), ruthenium (Ru), silver (Ag), molybdenum (Mo), niobium (Nb), antimony (Sb), technetium (Tc), xenon (Xe), and krypton (Kr). [0054] The buildup of fission products in the fuel salt composition 114 can impede or interfere with the nuclear fission in the reactor core 112 by poisoning the nuclear fission. For example, xenon-135 and samarium-149 can have a high neutron absorption capacity and they can lower the reactivity of the fuel salt composition 114. Fission products can also reduce the useful lifetime of the system 100 by clogging or corroding components, such as heat exchangers (e.g., 106, 130) or piping. Therefore, it can be desirable to keep concentrations of fission products in the fuel salt composition 114 below certain thresholds to maintain proper functioning of the system 100.

[0055] This goal can be accomplished by the fuel conditioning system 120. As discussed in greater detail below, the fuel conditioning system 120 can be configured to remove at least a portion of fission products generated in the fuel salt composition 114 during nuclear fission. As an example, the fuel salt composition 114 can be transported from the reactor core 112 to the fuel conditioning system 120, which can process the molten fuel salt composition 114 and allow the reactor 110 to function without loss of efficiency or degradation of components due to development of fission products. As shown in FIG. 1, the fuel conditioning system 120 can be contained within the reactor system 102 along with the reactor 110 and the primary heat exchanger 106. However, in alternative embodiments (not shown), at least one of the primary heat exchanger and the fuel-conditioning system can be located external to the reactor system.

[0056] FIG. 2 illustrates the fuel conditioning system 120 in greater detail. During normal operation of the reactor system 102, the fuel salt composition 114 can be circulated continuously or near-continuously from the reactor core 112 through one or more of functional sub-units of the fuel conditioning system 120 via fluid loop 146 by a pump 150. As discussed below, examples of the sub-units can include, but are not limited to, a corrosion reduction unit 152, a mechanical separation unit 154, and a chemical exchange unit 156. The fuel conditioning system 120 can also include a tank 160 for storage of excess fuel salt composition 114.

[0057] In an embodiment, the corrosion reduction unit 152 can be configured to inhibit or mitigate corrosion of components of the system 100 by the fuel salt composition 114. At least a portion of the reactor core 112 can be constructed of metallic alloy including one or more of the following elements: iron (Fe), nickel (Ni), chromium (Cr), manganese (Mn), carbon (C), silicon (Si), niobium (Nb), titanium (Ti), vanadium (V), phosphorus (P), sulfur (S), molybdenum (Mo), nitrogen (N), cermet alloys, stainless steels (austenitic stainless steels), zirconium alloys, or tungsten alloys, and variants thereof.

[0058] During operation of the system 100, the fuel salt composition 114 can be transported from the reactor core 112 to the corrosion reduction unit 152 and from the corrosion reduction unit 152 back to the reactor core 112. Transportation of the fuel salt composition 114 at a variably adjustable flow rate can be driven by the pump 150. The corrosion reduction unit 152 can be configured to process the fuel salt composition 114 to maintain an oxidation reduction (redox) ratio, E(o)/E(r), of the fuel salt composition 114 in the reactor core 112 (and elsewhere throughout the system 100) at a substantially constant level, where E(o) is an element (E) at a higher oxidation state (o) and E(r) is that element (E) at a lower oxidation state (r).

[0059] In one embodiment, the element (E) can be an actinide (e.g., uranium, U), E(o) can be U(IV) and E(r) can be U(III). In this embodiment, U(IV) can be in the form of uranium tetrachloride (UC1₄), U(III) can be in the form of uranium trichloride (UCI₃), and the redox ratio can be a ratio E(o)/E(r) of UCI₄/UCI₃. Although UCI₄ can corrode the reactor core 112 by oxidizing chromium according to:

Cr— > Cr³⁺ + 3e^~

Cr³⁺ + 3UCl₄→ CrCl₃ + 3UCl₃ the existence of UCI₄ can reduce the melting point of the molten fuel salt composition 114. Therefore, the level of the redox ratio, UCI₄/UCI₃, can be selected based on at least one of a desired corrosion reduction and a desired melting point of the fuel salt composition 114. For example, the redox ratio can be substantially constant and selected between about 1/50 to about 1/2000. More specifically, the redox ratio can be at a substantially constant level of about 1/2000.

[0060] The mechanical separation unit 154 can be configured to remove at least part of insoluble fission products and/or dissolved gas fission products from the fuel salt composition 114. Examples of insoluble fission products can include one or more of the following in any combination: krypton (Kr), xenon (Xe), palladium (Pd), ruthenium (Ru), silver (Ag), molybdenum (Mo), niobium (Nb), antimony (Sb), and technetium (Tc). Examples of gas fission products can include one or more of xenon (Xe) and krypton (Kr). As an example, the mechanical separation unit 154 can generate a froth from the fuel salt composition 114 that includes the insoluble fission products and/or the dissolved gas fission products. The dissolved gas fission products can be removed from the froth, and at least a portion of the insoluble fission products can be removed by filtration.

[0061] The chemical exchange unit 156 can be configured to remove at least a portion of the soluble fission products dissolved in the fuel salt composition 114. Examples of the soluble fission products can include one or more of the following, in any combination: rubidium (Rb), strontium (Sr), cesium (Cs), barium (Ba), and lanthanides. The removal of soluble fission products can be realized through various mechanisms.

[0062] Comprehensive lists of fission products applicable to various embodiments to the present disclosure are provided below. A person skilled in the art will appreciate that these lists are illustrative and not meant to be exhaustive.

[0063] Fission products sufficiently noble to maintain a reduced and insoluble state in the molten fuel salt composition 114 can include, but are not limited to:

• Germanium - 72, 73, 74, 76

• Arsenic - 75

• Selenium - 77, 78, 79, 80, 82

• Yttrium - 89

• Zirconium - 90 to 96

• Niobium - 95

• Molybdenum - 95, 97, 98, 100

• Technetium - 99

• Ruthenium - 101 to 106

• Rhodium - 103

•Palladium - 105 to 110

• Silver - 109

• Cadmium - 111 to 116

• Indium - 115

•Tin - 117 to 126

• Antimony - 121, 123, 124, 125

•Tellurium - 125 to 132 [0064] Fission products that can form gaseous products at the typical operating temperature of can include, but are not limited to:

• Bromine - 81

•Iodine - 127, 129, 131

•Xenon - 131 to 136

• Krypton - 83, 84, 85, 86

[0065] Fission products that can remain as chloride compounds in the molten fuel salt composition 114, in addition to actinide chlorides (Th, Pa, U, Np, Pu, Am, Cm) and carrier salt chlorides (Na, K, Ca), can include, but are not limited to:

• Rubidium - 85, 87

• Strontium - 88, 89, 90

•Cesium - 133, 134, 135, 137

•Barium - 138, 139, 140

• Lanthanides

o Lanthanum - 139

o Cerium - 140 to 144

o Praseodymium - 141, 143

o Neodymium - 142 to 146, 148, 150

o Promethium - 147

o Samarium - 149, 151, 152, 154

o Europium - 153, 154, 155, 156

o Gadolinium - 155 to 160

o Terbium - 159, 161

o Dysprosium - 161

[0066] FIG. 3 schematically illustrates components of a salt waste disposal system 500 that can be used to dispose of a salt waste produced by, for example, the system 100 of FIGS. 1-2. The salt waste disposal system 500 can include a chamber 502, a hot isostatic press (HIP) 504, and a vacuum pump 514. The chamber 502 can be a thin- walled vessel capable of compressing under the conditions exerted by the HIP 504 and it can be capable of contacting a chloride salt. For example, the chamber 502 can be formed from a copper material, a copper tube material, or another suitable material. In some examples, the wall of the chamber 502 can less than about 6 feet thick.

[0067] The HIP 504 can include a high-pressure containment vessel (HIP vessel) 532, connected to a gas source 516 over a gas conduit 526, and a heater 524 positioned within the HIP vessel 532. The heater 524 can connect to an energy source via a power connection 520 (e.g., a thermocouple or other suitable connection mechanism). The HIP 504 can be configured to subject the chamber 502 to both elevated temperature and isostatic gas pressure in the HIP vessel 532. In an embodiment, the gas source 516 can contain an inert gas (e.g., argon) for pressurizing the HIP vessel 532.

[0068] As an example, the chamber 502 can be positioned within the HIP vessel 532 and heated. Gas can also be pumped into the HIP vessel 532 to cause the pressure inside the HIP vessel 532 to increase. Each side of the chamber 502 can be exposed to elevated

temperatures and pressures within the HIP vessel 532. Thus, every side of the chamber 502 can be uniformly treated. The chamber 502 can remain in the HIP 504 for treatment under conditions and for a period that is sufficient to achieve the desired modification of the chamber 502. The pressure applied to the HIP vessel 532 can range between 500 and 20,000 PSI. The temperature within the HIP vessel 532 can range from about 500°F to about 3,000°F.

[0069] A treated chamber 506 can crushed and its height reduced. In addition, the microstructure of the treated chamber 506 can be improved. For example, a density of the treated chamber 506 can be greater than that of the chamber 502. The treated chamber 506 can be disposed of (e.g., sent to long-term storage).

[0070] FIG. 4 shows an exemplary embodiment of a method 902 of waste disposal consistent with the present disclosure. The method 902 can be suitable for disposing of waste from a fluid-fueled reactor, such as a molten salt nuclear reactor. Accordingly, the waste can be a waste salt extracted from the molten salt nuclear reactor. Non-limiting embodiments of the waste salt can include, actinides and fission products. As shown, the method 902 can include: mixing 915 a waste salt from a fluid-fueled reactor with silver chloride (AgCl) and with powdered silver to form a waste mixture. In certain embodiments, the mixing can include grinding the AgCl with the waste salt. The ratio of waste salt to AgCl can be about 1:5. In certain embodiments, the waste mixture can include about 2 wt.% powered silver. The method can also include sealing 917 the waste mixture within a chamber (e.g., chamber 502), evacuating 919 air around the waste mixture from the chamber, and treating 921 the chamber after sealing the waste mixture therein. A vacuum pump 514 (shown in FIG. 9) can be used to evacuate air from the chamber.

[0071] FIG. 5 shows an exemplary embodiment of a method 904 for treating a chamber containing the waste mixture. As discussed above, this treatment can improve the structural characteristics of the material from which the chamber is formed (e.g., to reduce voids within a microstructure of the chamber). Treating the chamber can include: positioning 923 the chamber within a hot isostatic press (e.g., HIP 504), pumping 925 an inert gas into the HIP, exerting a pressure from the range of about 500 psi to about 20,000 psi on the chamber by the inert gas, and, while the chamber is under pressure, raising 927 the temperature within the HIP to a level from the range of about 500°F to about 3,000°F for a time sufficient to reduce voids within a microstructure of the chamber. In an embodiment, the treatment can compress the chamber from a first height to a second height. The second height can be less than 99% of the first height. In certain embodiments, the chamber can be treated or conditioned multiple times under varying conditions (e.g., time, temperature, and/or pressure) to achieve the desired structural modifications.

[0072] The chamber, including the waste mixture sealed therein, can be disposed of after treatment. As an example, the chamber can be buried.

[0073] FIG. 6 shows an exemplary method 901 for forming a chamber to contain the waste mixture. In an embodiment, the chamber can be formed from a copper tube. The copper tube can have a thickness of less than about 10 cm. However, in alternative embodiments, other shapes for the chamber can be employed. The method 901 can include welding 903 an open end of a copper tube to form a first sealed end, adding 905 the waste mixture to the copper tube through the open end, evacuating 907 air from the copper tube, and welding 909 the open end of the copper tube to form a second sealed end and thereby sealing the waste mixture between the sealed ends. In certain embodiments, the waste mixture added to the chamber can be allowed to settle within the chamber before evacuating the air. In further embodiments, excess material beyond the sealed ends can be separated from the chamber.

[0074] All references cited throughout this application, for example patent documents including issued or granted patents or equivalents, patent application publications, and non-patent literature documents or other source material, are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application. For example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference.

[0075] One of ordinary skill in the art will appreciate that starting materials, biological materials, reagents, synthetic methods, purification methods, analytical methods, assay methods, and biological methods other than those specifically exemplified can be employed in the practice of embodiments of the disclosure without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in the disclosed embodiments.

[0076] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, including any isomers, enantiomers, and diastereomers of the group members, are disclosed separately.

[0077] When a Markush group, or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group are intended to be individually included in the disclosure.

[0078] When a compound is described herein such that a particular isomer, enantiomer, or diastereomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination. Additionally, unless otherwise specified, all isotopic variants of compounds disclosed herein are intended to be encompassed by the disclosure. For example, it will be understood that any one or more hydrogens in a molecule disclosed can be replaced with deuterium or tritium. Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently. [0079] As used herein, and in the appended claims, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art, and so forth. Additionally, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein.

[0080] As used herein, the term "comprising" is synonymous with "including," "having," "containing," and "characterized by" and each can be used interchangeably. Each of these terms is further inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0081] As used herein, the term "consisting of excludes any element, step, or ingredient not specified in the claim element.

[0082] As used herein, the term "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of," and "consisting of may be replaced with either of the other two terms.

[0083] The embodiments illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0084] The expression "of any of claims XX-YY" (where XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form and in some embodiments can be interchangeable with the expression "as in any one of claims XX-YY."

[0085] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the disclosed embodiments belong.

[0086] Whenever a range is given in the specification, for example, a temperature range, a time range, a composition range, or a concentration range, all intermediate ranges and subranges, as well, as all individual values included in the ranges given, are intended to be included in the disclosure. As used herein, ranges specifically include the values provided as endpoint values of the range. For example, a range of 1 to 100 specifically includes the end point values of 1 and 100. It will be understood that any subranges or individual values in a range or sub-range that are included in the description herein can be excluded from the claims herein.

[0087] In the descriptions above and in the claims, phrases such as "at least one of or "one or more of may occur followed by a conjunctive list of elements or features. The term "and/or" may also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it is used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases "at least one of A and Β;" "one or more of A and Β;" and "A and/or B" are each intended to mean "A alone, B alone, or A and B together." A similar interpretation is also intended for lists including three or more items. For example, the phrases "at least one of A, B, and C;" "one or more of A, B, and C;" and "A, B, and/or C" are each intended to mean "A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together." In addition, use of the term "based on," above and in the claims is intended to mean, "based at least in part on," such that an unrecited feature or element is also permissible.

[0088] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed embodiments. Thus, it should be understood that although the present application may include discussion of preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art. Such modifications and variations are considered to be within the scope of the disclosed embodiments, as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present disclosure and it will be apparent to one skilled in the art that they may be carried out using a large number of variations of the devices, device components, and methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional compositions and processing elements and steps.

Claims

1. A method of disposing of waste from a fluid-fueled reactor, the method

comprising:

mixing a waste salt from a fluid-fueled reactor with silver chloride (AgCl) and with powdered silver (Ag) to form a waste mixture;

sealing the waste mixture within a chamber;

evacuating air around the waste mixture from the chamber; and

treating the chamber after sealing the waste mixture therein.

2. The method of claim 1, wherein treating the chamber comprises:

positioning the chamber within a hot isostatic press (HIP);

pumping an inert gas into the HIP, the inert gas exerting a pressure selected from the range of about 500 psi to about 20,000 psi on the chamber; and

while the chamber is under pressure, raising the temperature within the HIP to a value from the range of about 500°F to about 3,000°F for a time sufficient to reduce voids within a microstructure of the chamber.

3. The method of claim 1, further comprising at least partially forming the chamber around the waste mixture, the chamber formation comprising:

welding an open end of a copper tube to form a first sealed end;

adding the waste mixture to the copper tube through the open end;

evacuating air from the copper tube; and

welding the open end of the copper tube to form a second sealed end and thereby sealing the waste mixture between the sealed ends.

4. The method of claim 1, further comprising, after treatment, disposing of the chamber including the waste mixture sealed therein.

5. The method of claim 4, wherein disposing of the chamber including the waste mixture comprises burying the chamber.

6. The method of claim 1, further comprising allowing the waste mixture to settle within the chamber before evacuating the air.

7. The method of claim 1, wherein the mixing includes grinding the waste salt with the AgCl.

8. The method of claim 1, wherein the chamber is formed from a copper material.

9. The method of claim 1, wherein the chamber is formed from a copper tube.

10. The method of claim 3, further comprising separating the chamber from excess material beyond the sealed ends.

11. The method of claim 1, wherein the chamber has a wall thickness of less than 10 cm.

12. The method of claim 1, wherein the waste mixture comprises a ratio of waste salt to AgCl of about 1:5.

13. The method of claim 1, wherein the waste mixture comprises 2 wt. % powdered silver.

14. The method of claim 1, wherein treating the chamber compresses the chamber from a first height to a second height.

15. The method of claim 14, wherein the second height is less than about 99% of the first height.

16. The method of claim 1, wherein the waste salt comprises actinides and fission products.

17. A waste disposal system for a fluid-fueled reactor, the waste disposal system comprising:

a chamber enclosing a waste mixture comprising a waste salt from a fluid-fueled reactor, silver chloride (AgCl), and powdered silver; and

a hot isostatic press (HIP) configured to reduce voids within a microstructure of the chamber.

18. The waste disposal system of claim 17, wherein the HIP comprises:

a vessel connected to a gas source via a gas conduit; and

at least one heater positioned within the vessel;

wherein the HIP is configured to exert a pressure selected from the range of about 500 psi to about 20,000 psi on the vessel.

19. The waste disposal system of claim 17, wherein the chamber is formed from a copper material.

20. The waste disposal system of claim 17, wherein the chamber is formed from a copper tube.

21. The waste disposal system of claim 17, wherein , wherein a ratio of waste salt to AgCl is about 1:5.

22. The waste disposal system of claim 17, wherein the waste mixture comprises about 2 wt. % powdered silver.

23. The waste disposal system of claim 17, wherein the waste salt comprises actinides and fission products.

24. A reactor system comprising:

a reactor comprising:

a reactor vessel,

a neutron reflector positioned within the reactor vessel to at least partially form one or more channels within the reactor vessel,

a heat exchanger connected to at least one of the channels, and a pump configured to circulate a fuel salt received within the reactor vessel via at least one of the channels; and

a waste disposal assembly in fluid communication with the reactor vessel and configured to receive, from the reactor vessel, a waste salt extracted from the fuel salt, wherein the waste disposal assembly comprises:

a chamber configured to receive a waste mixture comprising the waste salt, silver chloride (AgCl), and powdered silver; and