JP2024514626A - Zamak stabilization of spent sodium-cooled reactor fuel assemblies. - Google Patents

Abstract

Described herein is a method and system for stabilizing spent fuel assemblies from sodium-cooled nuclear reactors using zamak. A synergistic effect between zamak and sodium has been identified that allows zamak to form a thermally conductive interface with the sodium-wetted surfaces of the fuel assemblies. In this method, one or more spent fuel assemblies are removed from the sodium coolant pool and placed in a protective sheath. The remaining space in the sheath is then filled with liquid zamak. To some extent, the zamak will dissolve and form an alloy with the sodium remaining on the fuel assemblies. The excess sodium that remains undissolved is displaced from the sheath by the zamak filling. The zamak is then cooled until it becomes solid, and the sheath is sealed. Calculations indicate that the resulting zamak-stabilized spent fuel assemblies have sufficient internal thermal conductivity to be stored and transported without the need for liquid cooling.

Description

Detailed description of the invention

〔introduction〕
A method of disposing of spent nuclear fuel assemblies is needed. Spent fuel assemblies continue to generate heat, called decay heat. This is because the nuclear material within the assembly continues to fragment. If the decay heat is not removed, it can cause components within the fuel assembly to become unacceptably hot. Potentially, this could lead to component failure and release of nuclear material and fission products within the assembly.

To prevent overheating of the spent fuel assembly, "wet storage" is often employed, in which the spent fuel assembly is immersed in a large pool of water. The water pool acts as a coolant to remove decay heat produced by the spent fuel assembly. However, wet storage is not considered a long-term storage solution. This is because the integrity of the pool needs to be maintained. "Dry storage", which does not require liquid baths or other active cooling, is preferred for long-term storage. This allows for conventional storage of spent fuel assemblies at minimal cost.

One proposed method of stabilizing spent fuel assemblies for long-term dry storage is to fill the fuel assemblies with void-filling solid materials. A thermally conductive metal or metal alloy (e.g., lead) is heated above its melting point and flowed into the spent fuel assembly to cool the entire space within the fuel assembly (e.g., through the fuel assembly). channels provided for material flow) and then allowed to cool and solidify. Theoretically, if the spent fuel assembly is completely filled with metal, the thermal conductivity of the stabilized spent fuel assembly will rapidly transport decay heat to the outside of the fuel assembly; Dissipation to the external environment by natural convection and conduction may be sufficient to prevent the components from becoming unacceptably hot. Thus, in theory, spent fuel assemblies stabilized in this way could be transported and stored without the need for liquid cooling baths or other active cooling means.

However, research has revealed one major problem with this method: it has been found that gaps typically form between the investigated void-filling materials and the exterior surfaces of the components within the fuel assembly as the void-filling materials solidify. This gap reduces heat transfer between the fuel assembly components and the void-filling material to such an extent that this method is not viable.

[Zamak stabilization of spent sodium-cooled reactor fuel assemblies]
Described herein is a method and system for stabilizing spent fuel assemblies from sodium-cooled nuclear reactors using zamak. A synergistic effect has been identified between the use of zamak and sodium, which allows the zamak to form a thermally conductive interface with the sodium-wetted surfaces of the fuel assemblies. In this method, one or more spent fuel assemblies are removed from the sodium coolant pool and placed in a protective sheath. The remaining space in the sheath is then filled with liquid zamak. To a certain extent, the zamak dissolves with the sodium remaining on the fuel assemblies to form an alloy. The excess sodium that remains undissolved is displaced from the sheath by the zamak filling. The zamak is then cooled until it becomes solid, and the sheath is sealed. Calculations indicate that the resulting zamak-stabilized spent fuel assemblies have sufficient internal thermal conductivity to be stored and transported without the need for liquid cooling.

One drawback of metal stabilization (i.e., gap formation) is avoided by the method and system described herein. It has been determined that the primary cause of gap formation in early stabilization efforts is the presence of an oxide layer on the outer surfaces of the fuel assembly components. During normal reactor operation or subsequent wet storage, an oxide layer develops on the outer surfaces of the fuel assembly components due to contact with water, air or other oxygen-containing coolants. For example, it has been determined that at elevated temperatures, an oxide layer of several micrometers can develop after only a few seconds of exposure to air. A good metallurgical bond between the investigated void-filling material and the metal components of the fuel assembly is prevented by the oxide layer. In the absence of a good metallurgical bond at the interface between the fuel assembly components and the void-filling material, gaps form at the interface when the liquid void-filling material solidifies.

Formation of oxide layers on fuel assembly surfaces is prevented by the methods described herein. Unlike conventional pressurized water reactors, the fuel assembly in a sodium-cooled reactor is not exposed to oxygen, and the formation of an oxide layer on the fuel assembly is prevented by liquid sodium. By preventing subsequent exposure of the spent fuel assembly to oxygen during the process of removing the assembly from the sodium coolant pool and filling the assembly with zamak, oxide layer induced gap formation is prevented; A good metallurgical bond can be formed between the zamak and the outer surface of the fuel assembly.

[Brief explanation of the drawing]
Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings. The drawings are not intended to be drawn to scale. The drawings are included and constitute a part of this specification, and are included to provide illustration and further understanding of various aspects and embodiments. However, the drawings are not intended to define limitations of particular embodiments. The drawings, together with the remainder of the specification, serve to explain the principles and operation of the described and claimed aspects and embodiments. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For clarity, not all components in any figure are labeled.

FIG. 1 shows one embodiment of an integrated energy system with a sodium-cooled reactor.

Figure 2 is an exploded view of a fuel assembly for use in a sodium-cooled reactor.

FIG. 3 shows side views of different types of fuel assemblies.

Figure 4 shows one embodiment of a Zamak stabilization system suitable for use in the integrated energy system shown in Figure 1.

FIG. 5 depicts an alternative embodiment of the sheath that includes additional features (configurations) that could be implemented in any embodiment of the sheath.

FIG. 6 illustrates one embodiment of a method for stabilizing spent nuclear fuel assemblies from sodium cooled reactors using Zamak.

Detailed Description
Before disclosing and describing the method and system for zamac stabilization, it is to be understood that the present disclosure is not limited to the particular structures, process steps, components, or materials disclosed herein, but extends to equivalents thereof that one of ordinary skill in the art would recognize. It is also to be understood that the terminology used herein is used solely for the purpose of describing particular embodiments for stabilizing sodium-wet fuel assemblies, and is not intended to be limiting. It is to be noted that the singular forms "a,""an," and "the" as used herein include plural referents unless the context dictates otherwise. Thus, for example, a reference to "a lithium hydroxide" should not be construed as being quantitative or source limiting, a reference to "a step" may include a plurality of steps, a reference to "producing" or "products" of a reaction should not be construed as all of the products of the reaction, and a reference to "reacting" may include a reference to one or more such reaction steps. Thus, a reacting step may include multiple or repeated reactions of similar materials to produce a specified reaction product.

A method and system for stabilizing spent fuel assemblies from sodium-cooled nuclear reactors using zamak is described below. As discussed above, it has been determined that there is a synergy between zamak and sodium that allows zamak to form a thermally conductive interface with the sodium-wetted surfaces of the fuel assemblies. To a certain extent, zamak will dissolve and form an alloy with the sodium, but the effectiveness of the resulting sodium-enriched zamak as a stabilizing material is not reduced. Furthermore, because the density of liquid zamak is greater than that of liquid sodium, any excess liquid sodium can be easily displaced and collected from the fuel assemblies and sheaths during the zamak filling process.

Zamak refers to a family of alloys having the main component metal zinc and the alloying elements aluminum, magnesium and copper. Zamak alloys are part of the zinc-aluminum alloy family and are distinguished from other zinc-aluminum alloys by a constant nominal aluminum composition of 4% (substantially 3.5-4.3% by weight Al). Ru. Generally, zamac has 3.5-4.3% Al, 0.0-0.25% Cu and 0.01-0.02% Mg, with the balance being Zn. For the purposes of this document, Zamak alloys contain 1-10% Al; 0-1% Cu; 0.01-1% Mg; less than 0.5% impurities (in this case the impurities are Al, Cu , any element other than Mg and Zn); and the remaining Zn. Specifically, the ASTM B240 standard defines formulas for ingots of various members of the Zamak family. Some of the members of the Zamak family defined by ASTM B240 are Zamak 2, KS, Zamak 3, Zamak 4, Zamak 5, and Zamak 7. Any specific member of the Zamak family may be used herein. In one embodiment, Zamac 3 is used. The composition and properties of Zamak 3 are shown below. Compositions of other members of the Zamak family can be found within the ASTM B240 standard. The ASTM B240 standard is incorporated herein by reference.

In this method, one or more spent fuel assemblies are removed from a sodium coolant pool and placed within a protective sheath. The remaining space of the sheath is then filled with liquid zamak. To some extent, the zamak will dissolve and form an alloy with the remaining sodium on the fuel assembly. Excess sodium that remains undissolved is displaced from the sheath by filling with zamak. The zamak is then cooled until it becomes solid and the sheath is sealed. According to calculations, the resulting Zamak stabilized spent fuel assembly has sufficient internal thermal conductivity to be able to be stored and transported without the need for liquid cooling.

FIG. 1 depicts one embodiment of an integrated energy system 100 having a sodium cooled reactor 102. Sodium cooled reactor 102 includes a reactor vessel 104 containing a pool of sodium 106. One or more fuel assemblies 108 (three shown) containing nuclear fuel are immersed in a pool of sodium 106. Once immersed in sodium 106, the internal chamber of fuel assembly 108 is filled with sodium. Sodium 106 acts as a primary coolant, transferring heat from submerged fuel assembly 108 to the secondary coolant during operation. 3 and 4, the fuel assembly will be described in more detail.

In one design, as shown in FIG. 1, sodium within the pool is circulated between fuel assembly 108 and a submerged in-pool heat exchanger, referred to as primary heat exchanger 110. A circulation loop (indicated by liquid flow direction arrow 111) is formed in which heated sodium flows from fuel assembly 108 to primary heat exchanger 110 and cooled sodium flows back to fuel assembly 108.

The primary heat exchanger 110 cools the sodium by transferring heat into a secondary coolant, which may be sodium or some other fluid coolant, which circulates between the primary heat exchanger 110 and the secondary heat exchanger 112. In the illustrated embodiment, the secondary heat exchanger 112 transfers heat from the secondary coolant to a thermal storage medium. A supply of cold medium is provided in a cold reservoir 114. The secondary heat exchanger 112 transfers heat to the cold medium, which is then stored in a hot reservoir 116.

Heat storage is well known, and any suitable heat storage medium, now known or hereafter developed, may be used. In the illustrated embodiment, the heat storage medium is salt. Examples of suitable heat storage media include eutectic solutions, phase change materials, miscibility gap alloys, mixtures of metals (e.g. _AlSi12 ), cementitious materials, molten salts (e.g. one or more chloride salts of sodium, potassium and calcium; one or more nitrates of sodium, potassium and calcium (in particular NaKMg or NaKMgCl), solid or molten silicon, or these materials or Other material combinations are included.

When power from integrated energy system 100 is required, hot salt from hot tank 116 is passed through steam generator 118 . In steam generator 118, heat is transferred from the hot salt to the pressurized water stream to produce superheated steam. The (now cold) salt is sent to cryostat 114 and stored until it is needed to receive more heat from the secondary coolant.

Thermal energy in the superheated steam is converted to mechanical energy by passing the superheated steam through a conventional steam turbine and condenser system 120. In the illustrated embodiment, steam turbine 122 drives generator 124 to produce electricity.

In the illustrated embodiment, the reactor vessel 104 is capped by a vessel head 126. The vessel head 126 is provided with access ports that allow for the insertion and removal of fuel assemblies from the reactor vessel 104. A fuel assembly handling system 130 is provided for retrieving fresh fuel assemblies from a fuel assembly storage device 132, inserting and removing fuel assemblies 108 from the reactor 102, and transferring spent fuel assemblies 108 to a Zamak stabilization system 140. The fuel assembly handling system 130 maintains the fuel assemblies in an inert environment during handling to prevent exposure of the fuel assemblies to water, air, or any other undesirable environment, thereby inhibiting, if not preventing, the formation of an oxide layer on the surfaces of the fuel assemblies during transfer between the reactor vessel 104 and the Zamak stabilization system 140. In one embodiment, the fuel assembly handling system 130 maintains the fuel assemblies in a sodium environment during transfer. In an alternative embodiment, the fuel assemblies are maintained in an inert atmosphere, such as argon or nitrogen, during handling. In yet another embodiment, the fuel assembly handling system 130 maintains the fuel assembly in a low-oxygen environment having less than 0.1% oxygen, less than 0.01% oxygen, or less than 0.001% oxygen.

The zamak stabilization system 140 receives the spent fuel assembly from the handling system 130. The system 140 may be implemented to receive one or more spent fuel assemblies at a time. Additionally, the system 140 may be implemented to process the fuel assemblies one at a time, or may be implemented to process a batch or more at the same time. After receiving the spent fuel assembly, the zamak stabilization system 140 places it in a protective sheath. As described in more detail below, any free space within the fuel assembly 108 and the remaining space in the sheath around the fuel assembly 108 is filled with liquid zamak. Any excess sodium that remains undissolved is displaced from the sheath by the zamak filling and collected by the zamak stabilization system 140. The excess sodium may be reused within the reactor 102 or elsewhere in the integrated energy system 100. The zamak stabilization system 140 may then actively cool the sheathed spent fuel assembly until the zamak is solid. The zamak stabilization system 140 then seals the sheath (either before, during, or after cooling). The resulting sheathed zamak stabilized spent fuel assembly is calculated to have sufficient internal thermal conductivity to allow for storage and transportation without the need for liquid cooling. In one embodiment, the zamak stabilization system 140 maintains the spent fuel assembly in an inert environment during the stabilization process.

FIG. 2 is an exploded view of one embodiment of a fuel assembly 200 for use in a traveling wave reactor or other sodium cooled reactor. Assembly 200 includes an elongated coolant channel 202 having an axis A. Channel 202 has a hexagonal cross section. A handling socket 204 with an internal flow path is secured to the first end 206 of the channel 202 and has internal or external features. It may be gripped by mechanisms within the reactor vessel to raise, lower, and otherwise move assembly 200 into, out of, or within the reactor core, such as by internal or external features. Features make this possible. Inlet nozzle 208 is secured to second end 210 of channel 202 . A plurality of bearing rings 212 and a plurality of retaining rings 214 are used to attach the handling socket 204 and inlet nozzle 208 to the channel 202. A plurality of lock plates 216 (two in this example) and a plurality of rod strip rails 218 are included proximate the end of the inlet nozzle 208. A plurality of lock plates 216 and a plurality of rod strip rails 218 cooperate to connect fuel rod bundle 220 to inlet nozzle 208. In one embodiment, all of the fuel rods in fuel rod bundle 220 are annular metal fuel rods as described above. In an alternative embodiment, only some of the fuel rods are annular metal fuel rods, and other fuel rods may have different types or configurations. Seal ring 222 and flow restrictor 224 are also shown.

Figure 3 shows a side view of an alternative design of a fuel assembly 300. The assembly includes a set of fuel rods 320 that pass through and are held in place by a number of spacer grids 330 (six shown). A bottom nozzle assembly 340 supports the fuel assembly 300 in the reactor core. A top nozzle assembly 310 is provided at the top of the assembly 300 that includes a number of guide thimble tubes 302. The guide thimble tubes 302 extend from the top nozzle assembly 310 to the bottom nozzle assembly 340. The spacer grids 330 may be attached to the guide thimble tubes 302 for stability. A hold-down spring 312 is provided above the top nozzle assembly 310 at the top of the assembly 300 to ensure the proper amount of hold-down force against the fuel assembly components.

It should be noted that the fuel rods described above do not have to be uniform along their length. For example, regions of greater or lesser enrichment could be provided along the length of the fuel rod. This could be accomplished by providing different annular slugs of fuel or different particulate fuel in different regions during assembly. Similarly, burnable poisons, other additives, or different types of metallic fuel could be provided in specific regions. In addition to different materials, the different regions could have different attributes (e.g., different porosity, bulk density, or different annular slug sizes) even though the metallic fuel material remains the same.

The fuel assemblies of Figures 2 and 3 are just two examples of fuel assemblies that may be stabilized using the methods and systems described herein. Many other fuel assembly designs exist for use in other types of reactors. The configuration of the fuel rods and other types of rods (e.g., control rods, reflectors, and instrumentation rods) within a particular assembly for a particular reactor does not affect the Zamak stabilization technique. The shape and configuration of the rods within the assembly, and the shape, orientation, and configuration of the assembly in the reactor core may vary as appropriate for a particular reactor design and depending on the number, type, and performance of the annular metallic fuel rods used, but does not affect the stabilization process.

4 illustrates an embodiment of a zamak stabilization system suitable for use in the integrated energy system illustrated in FIG. 1. In the illustrated embodiment, the spent fuel assembly 402, when received by the zamak stabilization system 400, is placed into a sheath 404, which is then capped by an end cap 406. The sheath 404 is provided with a receptacle 410 that engages with a bottom nozzle 408 of the fuel assembly 402. Additional supports (not shown) may be provided within the sheath to guide the placement of the fuel assembly or provide additional support within the sheath prior to filling with zamak. In one embodiment, the receptacle 410 supports the fuel assembly 402 and allows for zamak to be injected into the fuel assembly 402 via the bottom nozzle 408 prior to filling the sheath 404 entirely with zamak. The receptacle 410 is connected to a lower access port 415 at the bottom of the sheath, through which the zamac is delivered by a pipe 416.

The sheath 404 may be made from any suitable material of construction. The sheath material must have a melting point higher than that of zamak and must maintain an adequate amount of strength at zamak operating temperatures. Zamak has a melting point of approximately 380-390°C. In one embodiment, the zamak is delivered at a temperature of 400-450°C when filling the fuel assembly and/or sheath chamber. In an alternative embodiment, the zamak temperature at delivery is 380-2,000°C.

Suitable materials for the sheath 404 and other components in the zamak flow loop include any suitable steel (e.g., stainless steels such as 304 steel, 316 steel, ferritic martensitic steels such as T-91, among others, or other non-corrosive materials having suitable melting points and strengths). Further examples of suitable steels include martensitic steels, ferritic steels, austenitic steels, stainless steels including aluminum-containing stainless steels, FeCrAl alloys, HT9, oxide dispersion strengthened steels, T91 steel, T92 steel, HT9 steel, 316 steel, 304 steel, advanced steels such as APMT (Fe-22 wt% Cr-5.8 wt% Al) and Alloy 33 (a mixture of iron, chromium, and nickel, nominally 32 wt% Fe-33 wt% Cr-31 wt% Ni). Unless otherwise specified, all percentages (%) herein are weight percentages (wt%). The steels may have any type of microstructure. For example, in one embodiment, substantially all of the steel in the cladding 106 has at least one phase selected from a tempered martensite phase, a ferrite phase, and an austenite phase. In one embodiment, the steel is HT9 steel or a modified version of HT9 steel.

A controllable valve 412 is provided that allows zamak to be directed into the bottom nozzle 408 or into the space between the sheath and the exterior surface of the spent fuel assembly. control. This allows filling the interior space of the fuel assembly accessible through the bottom and top nozzles independently of filling the exterior space between the sheath 404 and the exterior surface of the spent fuel assembly 402. Both spaces may be filled simultaneously or at staggered times. In the illustrated embodiment, valve 412 is within sheath 404. In an alternative embodiment, valve 412 may be external to sheath 404, allowing valve 412 to be reused. In this embodiment, the sheath has at least two access ports. One access port for filling the external space between the sheath 404 and the outer surface of the spent fuel assembly 402 and one access port for the fuel assembly 402 accessible through the bottom nozzle 408 and the top nozzle 414. is an access port for filling the internal space of the

When filling the interior space of the fuel assembly 402, excess sodium that does not alloy with the zamak is displaced by the heavier zamak and is eventually forced out of the top nozzle 414 and into the sheath chamber (i.e., the space between the sheath 404 and the outer surface of the spent fuel assembly 402). As the sheath chamber fills, the excess sodium is further displaced and eventually forced out of the sheath through an access port 418 in the sheath cap 406, which is connected to a zamak storage tank 420.

A sodium trap 422 is shown between the access port 418 and the zamak storage tank 420. In the illustrated embodiment, the sodium trap includes a sodium sensor 424, a controllable valve 426, and a sodium storage tank 428. When sodium is detected in the pipe, the valve directs the sodium into the sodium storage tank 428. When zamak is detected, the zamak is directed by the valve 426 to the zamak storage tank 420. The sodium trap 422 is only one possible method of collecting excess sodium from the sheath. Many other sodium trap designs or sodium trap strategies can be used to achieve the same result, and any suitable such designs or strategies may be utilized herein.

The flow of zamak through the zamak loop is driven by a pump 430. Additional components include sensors such as a temperature sensor 432 and a pressure sensor 434. Such sensors can be located throughout the system 400. In the illustrated embodiment, sensors are provided on both the zamak storage tank 420 and on the delivery pipe 416 just prior to the access port 415. A flow meter 436 is shown that allows the flow rate and volume of zamak delivered to the sheath to be monitored.

A controller 438 is provided to control the processes and operations of the various components. A controller 438 is communicatively connected to the sensors, controllable valves, pumps 430, and other components to receive data and send commands to various components based on processing of the received data. ing.

After the sheath and spent fuel assembly are filled with zamak, the sheath is sealed and removed from the loop. In one embodiment, the attachment pipes at the bottom and top are cut, shielded or sealed in any suitable manner. However, this is just one technique and any suitable alternative sealing and removal technique could be used.

Other components shown include a heater 440 for heating the zamak in the storage tank 420 and maintaining it in a liquid state during the stabilization process. In one embodiment, heater 440 may take the form of a resistance jacket heater around the exterior of storage tank 420.

Other components shown include a sheath cooler 442 for cooling the sheath 404 after filling with zamak. In one embodiment, cooler 442 could take any suitable form, including a fan that directs room temperature air outside of a cooling jacket or sheath. In yet another alternative, a temperature controlled room could be provided as a cooler 442. After the sheath is filled, sealed, and removed from the loop, it could be placed in a temperature-controlled room. The cooling of the zamak could then be precisely controlled. In one embodiment, as shown, the cooler is positioned to cool the bottom of the sheath 404 so that the zamak solidifies from the bottom upward.

Another component of the system 400 is a cover gas control system 450. The cover gas system 450 maintains a cover gas environment in the loop when zamak does not completely fill the loop. For example, when the fuel assembly 402 is initially placed into the sheath 404, the cover gas system 450 controls the environment around the fuel assembly and reduces the exposure of the fuel assembly 402 to oxygen to inhibit, if not prevent, the formation of a surface oxide layer on the fuel assembly. Cover gas systems are known in the art. Any suitable configuration for the system 450 may be used to reduce the exposure of the fuel assembly to oxygen before and during the zamak filling process.

FIG. 5 depicts an alternative embodiment of a sheath 500 showing additional configurations that could be implemented in any sheath embodiment.

In the illustrated embodiment, the sheath 504 and cap 506 are designed such that the sheath 504 is a unitary container with only a top opening that is covered by the cap 506. This makes the sheath easier to manufacture and reduces complexity. The sheath 504 is provided with a receptacle 510 that engages with the bottom nozzle 508 of the fuel assembly 502.

Two dip tubes 550 and 552 are provided so that the filling of zamak still occurs from the bottom. The fuel assembly dip tube 550 is fluidly connected to the receptacle 510 so that the zamak flowing through the fuel assembly dip tube 550 enters the fuel assembly 502 through the bottom nozzle 508. A second dip tube 552 is provided to fill the annular region between the fuel assembly and the sheath. In an alternative embodiment, this second dip tube is omitted and the annular region is filled by spilling zamak from the top nozzle 514 of the fuel assembly 502. An additional control valve 512 may be provided on the zamak inlet line to control/distribute the flow between the two dip tubes 550, 552. The dip tubes 550, 552 may be incorporated into the cap so that the dip tubes are properly positioned when the cap 506 and the sheath 504 are connected. Alternatively, the dip tubes 550, 552 may be incorporated into the sheath 504, with suitable corresponding openings provided in the cap 506.

Cap 506 is further provided with an outlet 554. When sheath 504 is filled, excess sodium and zamac will be removed via outlet 554. Each dip tube 550, 552 and outlet 554 may be provided with a connection valve 556 that can be closed after filling.

The sheath 504 can be easily cooled from the bottom using a cooler 542 connected to the bottom exterior of the sheath 504. Sheath 504 no longer has any fittings or connections to interact with the surroundings.

In the illustrated embodiment, the exterior of the sheath 504 is provided with two eyes 558 for handling and lifting of the sheath 504 before, during, and after filling.

FIG. 6 illustrates one embodiment of a method for stabilizing spent nuclear fuel assemblies from sodium cooled reactors using Zamak. In the illustrated embodiment, the method begins with removing a spent fuel assembly from a sodium cooled reactor in a removal operation 602. Removal operation 602 includes accessing a spent fuel assembly in a pool of sodium within a reactor vessel and removing the spent fuel assembly using a fuel assembly handling system. , may also be included. As explained in more detail below, during the transfer, the fuel assembly is maintained in a controlled environment with less than 0.1% oxygen, so that the fuel assembly is removed from the pool in this removal operation 602. The formation of an oxide layer on the surface of the fuel assembly during the completion of the zamak filling operation in 2 filling operation 612 is reduced.

The spent fuel assembly is then delivered to the Zamak stabilization system in a delivery operation 604.

In sheathing operation 606, once the spent fuel assembly is received, it is placed into a sheathing. In one embodiment of sheathing operation 606, the bottom nozzle of the fuel assembly is engaged with a receptacle at the bottom of the sheathing and the sheathing is capped. The now sealed sheath is then connected to the Zamak piping.

In a zamak production operation 608, liquid zamak is produced by heating a quantity of zamak to a temperature above its melting point, if the zamac has not already been heated to its liquid operating temperature.

A first filling operation 610 is performed to fill the internal chamber(s) of the spent nuclear fuel assembly with liquid zamak by flowing the liquid zamak through the receptacle of the sheath and the bottom nozzle of the fuel assembly. Excess sodium is displaced (displaced, removed) from the top nozzle of the fuel assembly. The sodium may be collected from the top nozzle or may be allowed to accumulate in the annular space between the exterior of the fuel assembly and the sheath if zamak has not yet filled that area.

A second filling operation 612 is performed to fill the annular space between the outer surface of the fuel assembly and the sheath with zamak. Again, excess sodium on the outer surface of the fuel assembly will be dislodged as the space is filled and will float to the surface of the zamak. In one embodiment, the annular space between the outer surface of the fuel assembly and the sheath may be filled through a sheath access port at the bottom of the sheath. Alternatively, the annular space between the outer surface of the fuel assembly and the sheath is filled by passing additional zamak through the fuel assembly and allowing excess zamak to overflow from the top nozzle of the fuel assembly until the annular space is filled. may be done. A second filling operation 612 may be performed until all of the excess sodium is removed from the sheath and the zamak flows out of the sheath. Any excess sodium displaced from the sheath may be collected and stored for later cleaning and/or reuse in the reactor pool.

In one embodiment, after filling, an excess amount of zamak may be flushed through either the sheath or the fuel assembly so that the filled components are flushed with additional zamak. The amount of surplus zamak to be flushed into a space may be determined based on the size of that space, as will be known. Alternatively, the zamak may be flushed based on the time after the initial fill (e.g., the sheath is filled to reduce unfilled areas or to displace residual sodium). (after which the zamak is allowed to flow through the sheath for 10 minutes).

In yet another embodiment, no excess sodium or zamac is removed from the sheath. Rather, the sheath is only filled to the point that the fuel assembly is partially or completely submerged in the zamak, and then the sheath is sealed. In this embodiment, all sodium from the reactor remains within the sheath and is disposed of with the final stabilized fuel assembly. This embodiment reduces the amount of irradiated sodium handled, although sodium may be wasted.

In one embodiment, the flow of zamac into the bottom nozzle of the fuel assembly and into the sheath can be controlled independently. This allows the first filling operation 610 and the second filling operation 612 to occur in any order. For example, in one embodiment, the first filling operation 610 occurs first and the second filling operation 612 occurs only after the fuel assembly is filled. The first filling operation 610 and the second filling operation 612 may be assisted by vibrating the sheath during the filling operations.

A cooling operation 614 is then performed on the zamak filled sheath. As mentioned above, the cooling process may be active or passive. In one embodiment, a cooler is used to cool the sheath from below so that the bottom portion of the zamak solidifies first. The cooling rate may be controlled. The zamak is cooled below its melting point. The zamak may be further cooled to room temperature.

Once cooled, the sheathed zamak stabilized fuel assembly is ready for dry storage as indicated by dry storage operation 616. This may include placing the sheathed zamak stabilized fuel assembly outdoors, in a building, or underground in a borehole or other chamber. The sheathed zamak stabilized fuel assembly may further be placed in a cask, frame, or other container to aid in transportation or storage.

Either or both of the removal operation 602 and the delivery operation 604 may include a drainage operation in which liquid sodium is allowed to drain from the spent nuclear fuel assembly, thereby reducing or even eliminating the amount of excess sodium that is recovered when filling the sheath.

In one embodiment of the stabilization method 600, all of the operations of the method are performed without exposing the spent fuel assembly to an environment having more than 0.1% oxygen, so as to prevent the formation of oxides on the surface of the fuel assembly. This may be done by maintaining the spent fuel assembly in an inert atmosphere (i.e., an atmosphere of one or more inert gases such as argon, nitrogen, and helium having less than 0.1% oxygen by weight), a low-oxygen atmosphere (e.g., less than 0.1% oxygen by weight, less than 0.01% oxygen by weight), or a sodium environment during handling of the spent fuel assembly. In an alternative embodiment, the removal operation 604 and the delivery operation 606 may be performed quickly, relying on the sodium wetting of the spent fuel to prevent any substantial formation of oxides. If the filling operation inside the sheath is performed in an inert or sodium environment, the displaced inert material or sodium may be collected for reuse.

In an alternative embodiment of method 600, the sheath is omitted. In this embodiment, the spent fuel assembly is filled with zamak, the nozzle is sealed, and the zamak is cooled, resulting in a zamak stabilized but unsheathed spent fuel assembly. In an embodiment, this simpler approach may be sufficient if decay heat generation is minimal.

Although described in the context of the disposal of spent fuel assemblies, the systems and methods described above are applicable to new fuel assemblies, whether or not they contain nuclear material that produces decay heat, or others exposed to sodium. could be used to stabilize any component of the For example, in one embodiment, the systems and methods described above could be used to dispose of metal components, such as pipes that held sodium or were in a sodium environment. A zamak stabilization system can be used to fill a tube with zamac to displace residual sodium within the tube, and then cool the stabilized tube to prepare it for storage and/or disposal. It would be possible to create a finished Zamak stabilizing tube.

Notwithstanding the appended claims, the present disclosure is also defined by the following numbered clauses:

1.
1. A method for preparing a spent nuclear fuel assembly for storage, comprising the steps of:
the spent nuclear fuel assembly having an exterior and one or more interior chambers accessible through a bottom nozzle and a top nozzle;
providing a quantity of zamak having a first melting point;
providing a sheath made from a material having a second melting point higher than the first melting point, the sheath further including a receptacle configured to engage the bottom nozzle of the spent nuclear fuel assembly;
removing the spent nuclear fuel assembly from the liquid sodium environment;
placing the spent nuclear fuel assembly within a sheath and engaging the receptacle with the bottom nozzle;
generating liquid zamak by heating the quantity of zamak to a temperature above the first melting point but below the second melting point;
filling one or more of the internal chambers of the spent nuclear fuel assembly with liquid zamak by flowing liquid zamak through the receptacle and the bottom nozzle;
filling the sheath with liquid zamak by flowing liquid zamak into a space between the sheath and the exterior of the spent nuclear fuel assembly until the sheath is filled with liquid zamak;
A method comprising:

2.
2. The method according to clause 1, wherein said zamak is selected from zamak 2, KS, zamak 3, zamak 4, zamak 5 and zamak 7.

3.
The method according to clause 1, wherein the Zamak is Zamak 3.

4.
4. A method according to any one of clauses 1 to 3, further comprising, after filling the sheath with liquid zamak, cooling the zamak in the sheath to a temperature below the first melting point.

5.
placing the spent nuclear fuel assembly within the sheath in an inert environment;
filling the sheath with liquid zamak, thereby displacing the inert environment;
5. The method of any one of clauses 1 to 4, further comprising:

6.
A method according to any one of clauses 1 to 5, wherein the material having a second melting point higher than the first melting point is selected from 304 stainless steel, 316 stainless steel, and T91 steel.

7.
7. The method of any one of clauses 1-6, further comprising draining liquid sodium from the spent nuclear fuel assembly.

8.
8. The method of any one of clauses 1-7, further comprising collecting sodium displaced from the sheath and one or more of the internal chambers by a plurality of the filling operations.

9.
The placement operation is
The method of any one of clauses 1-8, further comprising the step of capping the sheath after the step of placing the spent nuclear fuel assembly within the sheath.

10.
9. The method of any one of clauses 1-8, further comprising cooling the sheath after filling the sheath and the one or more internal chambers with zamak.

11.
The cooling operation is
11. The method of claim 10, further comprising the step of cooling the sheath from the bottom.

12.
12. The method of any one of clauses 1-11, further comprising the step of placing the sheath in a dry storage device after the step of filling the sheath and the one or more internal chambers with zamak.

13.
12. The method of any one of clauses 1-11, further comprising the step of placing the sheath in a dry underground storage site after the step of filling the sheath and the one or more internal chambers with zamak.

14.
preventing the formation of oxides on at least one surface of the spent nuclear fuel assembly between removing the spent nuclear fuel assembly from the sodium environment and filling the spent nuclear fuel assembly with liquid zamak; 14. The method according to any one of clauses 1 to 13, further comprising a step.

15.
14. The method of any one of clauses 1-13, further comprising inhibiting formation of an oxide layer on a surface of the spent nuclear fuel assembly by maintaining the spent nuclear fuel assembly in a low-oxygen environment.

16.
Clause 1, wherein one or more operations of the method are performed in one of an inert atmosphere or a low oxygen atmosphere to inhibit the formation of an oxide layer on the surface of the spent nuclear fuel assembly. The method according to any one of items 1 to 13.

17.
1. A method of preparing spent nuclear fuel assemblies for storage, the method comprising:
providing an amount of zamak having a first melting point;
removing the spent nuclear fuel assembly from a liquid sodium environment while controlling exposure of the spent nuclear fuel assembly to oxygen, thereby inhibiting the formation of an oxide layer on the spent nuclear fuel assembly; and,
filling the spent nuclear fuel assembly with the zamak in a liquid state so as to obtain a zamak-filled spent nuclear fuel assembly, thereby dissolving at least a portion of the liquid sodium in the spent nuclear fuel assembly into the zamac; and removing remaining liquid sodium from the spent nuclear fuel assembly;
cooling the Zamak-filled spent nuclear fuel assembly until the Zamak has a temperature below the first melting point to obtain a Zamak-stabilized spent nuclear fuel assembly;
dry storing the Zamak stabilized spent nuclear fuel assembly;
including methods.

18.
The filling operation includes:
placing the spent nuclear fuel assembly within a sheath made of a material having a second melting point higher than the first melting point;
filling both the sheath and the spent nuclear fuel assembly with liquid zamak;
The method according to clause 17, further comprising:

19.
19. A method according to clause 17 or 18, wherein the Zamak is selected from Zamak 2, KS, Zamak 3, Zamak 4, Zamak 5, and Zamak 7.

20.
19. The method according to clause 17 or 18, wherein the Zamak is Zamak 3.

21.
21. The method of any one of clauses 17-20, further comprising, after filling the sheath with liquid zamak, cooling the zamak in the sheath to a temperature below the first melting point.

22.
placing the spent nuclear fuel assembly within the sheath in an inert environment;
filling the sheath with liquid zamak, thereby replacing the inert environment;
22. The method of any one of clauses 17 to 21, further comprising:

23.
23. The method of any one of clauses 17-22, wherein the material having a second melting point higher than the first melting point is selected from 304 stainless steel, 316 stainless steel, and T91 steel.

24.
24. The method of any one of clauses 17-23, further comprising draining liquid sodium from the spent nuclear fuel assembly.

25.
25. The method of any one of clauses 17-24, further comprising collecting sodium displaced from the sheath and the spent nuclear fuel assembly by a plurality of the filling operations.

26.
The arrangement operation is
26. The method of any one of clauses 17-25, further comprising capping the sheath after placing the spent nuclear fuel assembly within the sheath.

27.
27. The method of any one of clauses 17-26, further comprising cooling the sheath after filling the sheath and the spent nuclear fuel assembly with zamak.

28.
The cooling operation is
28. The method of claim 27, further comprising the step of cooling the sheath from the bottom.

29.
29. The method of any one of clauses 17-28, further comprising placing the sheath in a dry storage device after filling the sheath and the spent nuclear fuel assembly with Zamak.

30.
29. The method of any one of clauses 17-28, further comprising placing the sheath in a dry underground storage location after filling the sheath and the spent nuclear fuel assembly with Zamak.

31.
31. A method according to any one of clauses 17 to 30, wherein the method is carried out without exposing the spent nuclear fuel assembly to oxygen.

32.
31. The method of any one of clauses 17-30, wherein one or more operations of the method are performed without exposing the spent nuclear fuel assembly to oxygen.

33.
33. The method of any one of clauses 17 to 32, wherein one or more operations of the method are carried out in an inert atmosphere.

34.
An apparatus comprising a fuel assembly filled with solid zamak.

35.
35. The apparatus of clause 34, wherein the fuel assembly is sealed within a container.

36.
36. The apparatus of clause 35, wherein the space between the fuel assembly and the container is filled with solid zamak.

37.
A system for stabilizing a spent nuclear fuel assembly derived from a sodium cooled nuclear reactor, the system comprising:
Zamak storage tank;
an amount of zamak having a melting point;
a sheath configured to receive and hermetically retain the spent nuclear fuel assembly, the sheath having an inlet port for receiving and injecting liquid zamak into the sheath;
a heater adapted to heat the zamak to a temperature above the melting point;
A system equipped with.

38.
38. The system of clause 37, further comprising a controller configured to control the flow of liquid zamak into the sheath.

39.
38. The system of clause 37, further comprising a cooler adapted to cool the sheath and its contents below the melting point.

40.
38. The system of claim 37, further comprising a sodium trap configured to collect liquid sodium from the sheath.

41.
38. The system of clause 37, further comprising the sodium cooled nuclear reactor including a sodium pool housing a plurality of fuel assemblies.

42.
42. The system of clause 41, further comprising a fuel assembly handling system adapted to transfer a plurality of fuel assemblies from the sodium pool to the sheath.

43.
43. The system of any one of clauses 37-42, further comprising a cover gas system adapted to maintain the spent nuclear fuel assembly under a hypoxic environment.

44.
The system and method of any one of clauses 1-43, wherein sodium-exposed components are stabilized in place of spent nuclear fuel assemblies.

45.
1. A method of preparing a component for storage having a surface exposed to sodium, the method comprising:
providing an amount of zamak having a first melting point;
displacing sodium from the surface by liquid zamac so that a zamac-coated surface is obtained on the component;
cooling the zamak to a temperature below the first melting point so as to obtain a zamak stabilizing component;
including methods.

46.
the component is a sodium-filled tube;
The process of moving is
46. The method of clause 45, further comprising filling the tube with liquid zamak.

47.
The zamac contains 1-10% Al; 0-1% Cu; 0.01-1% Mg; less than 0.5% impurities (i.e. any element other than Al, Cu, Mg and Zn). and an alloy having a balance of Zn.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like used in the specification and claims are to be understood as being modified in all instances by the word "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought.

Notwithstanding that the numerical ranges and numerical parameters describing a wide range of techniques are approximations, the numerical values set forth in the specific examples are reported to be as accurate as possible. However, any numerical value inherently contains certain errors that necessarily result from the standard deviation found in each test measurement.

It will be apparent that the systems and methods described herein are well adapted to achieve the objects and advantages mentioned, as well as those inherent therein. Those skilled in the art will recognize that the methods and systems described herein may be implemented in many ways and are not limited by the exemplary embodiments and examples described above. In other words, functional elements may be performed by single or multiple components in various combinations of hardware and software, and individual functions may be distributed among software applications at either the client or server level. In this regard, any number of features of the various embodiments described herein may be combined into a single embodiment, and alternative embodiments having fewer or more features than all of the features described herein are contemplated.

While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made that are well within the scope contemplated by this disclosure. For example, the reader will immediately be aware of numerous alternative embodiments of the basic design shown in FIG. 1. For example, the secondary heat exchanger 112 may be omitted, and a thermal storage medium may be used as the secondary coolant. Eliminating the intermediate thermal loop simplifies the structure, piping, and valves, and reduces costs. Many other modifications may be made that are readily suggested to those skilled in the art and are within the spirit (intent) of this disclosure.

1 illustrates an embodiment of an integrated energy system with a sodium cooled reactor. FIG. 1 is an exploded view of a fuel assembly for use in a sodium-cooled reactor. Figure 3 shows side views of different types of fuel assemblies. 2 illustrates an embodiment of a zamak stabilization system suitable for use in the integrated energy system illustrated in FIG. 13 illustrates an alternative embodiment of a sheath that includes additional features that could be implemented in any of the sheath embodiments. 1 illustrates an embodiment of a method for stabilizing spent nuclear fuel assemblies from a sodium-cooled reactor using zamak.

Claims (45)

1. A method for preparing a spent nuclear fuel assembly for storage, comprising the steps of:
the spent nuclear fuel assembly having an exterior and one or more interior chambers accessible through a bottom nozzle and a top nozzle;
providing a quantity of zamak having a first melting point;
providing a sheath made from a material having a second melting point higher than the first melting point, the sheath further including a receptacle configured to engage the bottom nozzle of the spent nuclear fuel assembly;
removing the spent nuclear fuel assembly from the liquid sodium environment;
placing the spent nuclear fuel assembly within a sheath and engaging the receptacle with the bottom nozzle;
generating liquid zamak by heating the quantity of zamak to a temperature above the first melting point but below the second melting point;
filling one or more of the internal chambers of the spent nuclear fuel assembly with liquid zamak by flowing liquid zamak through the receptacle and the bottom nozzle;
filling the sheath with liquid zamak by flowing liquid zamak into a space between the sheath and the exterior of the spent nuclear fuel assembly until the sheath is filled with liquid zamak;
A method comprising: 2. The method of claim 1, wherein the Zamak is selected from Zamak 2, KS, Zamak 3, Zamak 4, Zamak 5 and Zamak 7. 2. The method of claim 1, wherein the Zamac is Zamac 3. The method according to any one of claims 1 to 3, further comprising, after the step of filling the sheath with liquid zamak, a step of cooling the zamak in the sheath to a temperature below the first melting point. placing the spent nuclear fuel assembly within the sheath in an inert environment;
filling the sheath with liquid zamak, thereby displacing the inert environment;
The method according to any one of claims 1 to 4, further comprising: A method according to any preceding claim, wherein the material having a second melting point higher than the first melting point is selected from 304 stainless steel, 316 stainless steel and T91 steel. The method of any one of claims 1 to 6, further comprising the step of draining liquid sodium from the spent nuclear fuel assembly. The method of any one of claims 1 to 7, further comprising collecting sodium displaced from the sheath and one or more of the internal chambers by a plurality of the filling operations. The placement operation is
The method of any one of claims 1 to 8, further comprising the step of: capping the sheath after the step of placing the spent nuclear fuel assembly within the sheath. A method according to any preceding claim, further comprising cooling the sheath after filling the sheath and one or more of the internal chambers with zamak. The cooling operation is
The method of claim 10 further comprising the step of: cooling the sheath from the bottom. A method according to any preceding claim, further comprising the step of placing the sheath in a dry storage device after filling the sheath and one or more of the internal chambers with zamak. A method according to any preceding claim, further comprising the step of placing the sheath in a dry underground storage location after filling the sheath and one or more of the internal chambers with zamak. The method of any one of claims 1 to 13, further comprising the step of preventing oxide formation on at least one surface of the spent nuclear fuel assembly between the step of removing the spent nuclear fuel assembly from the sodium environment and the step of filling the spent nuclear fuel assembly with liquid zamak. The method of any one of claims 1 to 13, further comprising inhibiting the formation of an oxide layer on the spent nuclear fuel assembly by maintaining the spent nuclear fuel assembly in a low-oxygen environment. 10. The method of claim 1, wherein one or more operations of the method are performed in one of an inert atmosphere or a low oxygen atmosphere to inhibit the formation of an oxide layer on the surface of the spent nuclear fuel assembly. 14. The method according to any one of 1 to 13. 1. A method of preparing spent nuclear fuel assemblies for storage, the method comprising:
providing an amount of zamak having a first melting point;
removing the spent nuclear fuel assembly from a liquid sodium environment while controlling exposure of the spent nuclear fuel assembly to oxygen, thereby inhibiting the formation of an oxide layer on the spent nuclear fuel assembly; and,
filling the spent nuclear fuel assembly with the zamak in a liquid state so as to obtain a zamak-filled spent nuclear fuel assembly, thereby dissolving at least a portion of the liquid sodium in the spent nuclear fuel assembly into the zamac; and removing remaining liquid sodium from the spent nuclear fuel assembly;
cooling the Zamak-filled spent nuclear fuel assembly until the Zamak has a temperature below the first melting point to obtain a Zamak-stabilized spent nuclear fuel assembly;
dry storing the Zamak stabilized spent nuclear fuel assembly;
including methods. The filling operation is
placing the spent nuclear fuel assembly within a sheath made from a material having a second melting point higher than the first melting point;
filling both the sheath and the spent nuclear fuel assembly with liquid zamak;
20. The method of claim 17, further comprising: 19. A method according to claim 17 or 18, wherein the Zamak is selected from Zamak 2, KS, Zamak 3, Zamak 4, Zamak 5, and Zamak 7. 19. The method according to claim 17 or 18, wherein the Zamac is Zamac 3. The method according to any one of claims 17 to 20, further comprising, after the step of filling the sheath with liquid zamak, a step of cooling the zamak in the sheath to a temperature below the first melting point. placing the spent nuclear fuel assembly within the sheath in an inert environment;
filling the sheath with liquid zamak, thereby displacing the inert environment;
22. The method according to any one of claims 17 to 21, further comprising: The method of any one of claims 17 to 22, wherein the material having a second melting point higher than the first melting point is selected from 304 stainless steel, 316 stainless steel, and T91 steel. 24. A method according to any one of claims 17 to 23, further comprising draining liquid sodium from the spent nuclear fuel assembly. The method of any one of claims 17 to 24, further comprising collecting sodium displaced from the sheath and the spent nuclear fuel assembly by a plurality of the filling operations. The arrangement operation is
26. The method of any one of claims 17 to 25, further comprising capping the sheath after placing the spent nuclear fuel assembly within the sheath. 27. The method of any one of claims 17 to 26, further comprising cooling the sheath after filling the sheath and the spent nuclear fuel assembly with Zamak. The cooling operation includes:
28. The method of claim 27, further comprising: cooling the sheath from the bottom. 29. The method of any one of claims 17 to 28, further comprising placing the sheath in a dry storage device after filling the sheath and the spent nuclear fuel assembly with Zamak. 29. The method of any one of claims 17 to 28, further comprising placing the sheath in a dry underground storage location after filling the sheath and the spent nuclear fuel assembly with Zamak. A method according to any one of claims 17 to 30, wherein the method is carried out without exposing the spent nuclear fuel assembly to oxygen. The method of any one of claims 17 to 30, wherein one or more operations of the method are performed without exposing the spent nuclear fuel assembly to oxygen. 33. A method according to any one of claims 17 to 32, wherein one or more operations of the method are carried out in an inert atmosphere. An apparatus comprising a fuel assembly filled with solid zamak. 35. The apparatus of claim 34, wherein the fuel assembly is sealed within a container. The apparatus of claim 35, wherein the space between the fuel assembly and the container is filled with solid zamak. 1. A system for stabilizing spent nuclear fuel assemblies from a sodium-cooled nuclear reactor, comprising:
Zamak storage tanks;
an amount of zamak having a melting point;
a sheath configured to receive and hermetically retain the spent nuclear fuel assembly, the sheath having an inlet port for receiving and injecting liquid zamak into the sheath;
a heater adapted to heat the zamak to a temperature above said melting point;
A system comprising: 38. The system of claim 37, further comprising a controller configured to control the flow of liquid zamak into the sheath. 38. The system of claim 37, further comprising a cooler adapted to cool the sheath and its contents below the melting point. 38. The system of claim 37, further comprising a sodium trap configured to collect liquid sodium from the sheath. 38. The system of claim 37, further comprising the sodium cooled nuclear reactor including a sodium pool housing a plurality of fuel assemblies. The system of claim 41, further comprising a fuel assembly handling system adapted to transfer a plurality of fuel assemblies from the sodium pool to the sheath. The system of any one of claims 37 to 42, further comprising a cover gas system adapted to maintain the spent nuclear fuel assembly in a low-oxygen environment. 1. A method for preparing a component having a sodium-exposed surface for storage, comprising:
providing a quantity of zamak having a first melting point;
displacing sodium from said surface by liquid zamak such that a zamak coated surface is obtained on said component;
cooling the zamak to a temperature below the first melting point to obtain a zamak-stabilized component;
A method comprising: the component includes a sodium-filled tube;
The process of moving is
45. The method of claim 44, further comprising: filling the tube with liquid zamak.

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