GB2605164A

GB2605164A - Composite material for fusion reactor first-wall and method of making the same

Info

Publication number: GB2605164A
Application number: GB2104135.5A
Authority: GB
Inventors: Kanyanta Valentine
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 2021-03-24
Filing date: 2021-03-24
Publication date: 2022-09-28
Also published as: GB202104135D0

Abstract

A composite material for forming a first wall of a fusion reactor comprises first 20 and second 30 materials that each have a continuous, interpenetrating, three-dimensional structure. The first material is a metal (e.g. a refractory metal, W, Ta, Mo or Ti, steel, an oxide dispersed steel, Fe-Cr-Al, Ti6Al4V) and the second material is a ceramic (e.g. a carbide, an oxide, a nitride or diamond). The composite is made by forming the first three-dimensional structure from a metal by injection moulding, 3D printing, robocasting or filling a sacrificial template with metal powder, pressing or sintering and then removing the template. The second material can be formed simultaneously with 3D printing the first material or interpenetrating the first structure with a powder or slurry which is then sintered.

Description

Composite Material for Fusion Reactor First-Wall and Method of Making the Same [0001] The present invention relates to a composite to form a first wall of a nuclear reactor and a method of manufacturing said composite.

[0002] The interior lining of a nuclear fusion reactor, such as a tokamak, is known as a first wall and comprises a plasma-facing surface. The first wall experiences a combination of extreme operating conditions such as high thermal-mechanical loads, high neutron radiation doses, fracture, creep, fatigue, erosion, plasma interactions, etc. For example, the first wall of the fusion reactor may experience operating temperatures of up to 1000°C, high neutron irradiation (in the order of 14.1 MeV) and an accumulated lifetime neutron induced damages of over 150 dpa and high heat fluxes of 10-20 MW/m2. The first wall may also be susceptible to high temperature effects such as creep, softening, precipitation and recrystallisation, corrosion, erosion and plasma exposure. It is desirable to identify a suitable material for a first wall with an improved capability of withstanding these conditions.

[0003] According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent

claims, and the description which follows.

[0004] According to an aspect of the invention, there is provided a composite for forming a first wall of a fusion reactor, the composite comprising first and second materials that each have a continuous three-dimensional structure, wherein the structures of the first and second materials are interpenetrating, and wherein the first material comprises a metal or metal alloy and the second material comprises a ceramic.

[0005] The use of a composite as a first wall material may combine the structural properties required for a first wall with the plasma-facing properties required for a plasma-facing surface. The use of the composite as the first wall material may combine fracture resistance and high thermal conductivity properties of the metal, and thermal and erosion resistance and neutron shielding properties of the ceramic. Existing monolithic first walls formed of ceramics may have a high resistance to neutron damage, the ability to work at high temperatures without suffering from creep, softening, precipitation and recrystallisation, resistance to high temperature corrosion, the ability to handle high heat fluxes and resistance to plasma sputtering and erosion. However, ceramics are highly susceptible to fracture under load due to their inherently low fracture toughness. The use of the 3D interpenetrated metallic structure in the composite provides a required toughness and hence structural integrity.

[0006] The first material being metal may promote structural integrity and provide high fracture toughness, which may compensate for a susceptibility to fracture of the second, ceramics, material. The first material being metal may also provide high thermal conductivity and a means of quickly conducting or dissipating heat away from the second material if required. The second material being ceramics may provide a high resistance to creep, thermal damage and high heat fluxes, a high resistance to plasma erosion, a high resistance to neutron damage, high neutron shielding properties and high resistance to thermal cycling and fatigue.

[0007] Providing the first and second materials in the composite as continuous three-dimensional structures that are interpenetrating may provide the advantage that the properties of the first and second materials may be combined, without a trade-off of properties, which may occur in particle composites. Furthermore, the interpenetrating three-dimensional composite may have improved reliability compared to a functionally graded composite, which may be prone to delamination and premature failure due to high residual stresses at the interface of different materials.

[0008] The first material may have a melting temperature of at least 1200°C, typically, a melting temperature of at least 1600°C, such as at least 2000°C.The first material may have a melting temperature of less than 3600°C, typically, a melting temperature of less than 2700 °C, such as less than 2000°C. The first material may have a melting temperature of between 1200 and 2700°C, typically, a melting temperature of between 1600 and 2300°C, such as between 1800 and 2000 °C.

[0009] The second material may have a melting temperature of at least 1200°C, typically a melting temperature of at least 2000°C, such as at least 2200°C. The second material may have a melting temperature of less than 3000°C, typically, a melting temperature of less than 2800°C, such as less than 2600°C. The second material may have a melting temperature of between 1200 and 3000°C, typically, between 2000 and 2800°C, such as between 2200 and 2600°C.

[0010] The first material may comprise a metal selected from group IV-VIII metals. The first material may be a metal alloy, such as steel, EUROFER97 (14%Cr oxide dispersion strengthened (ODS) steels), FeCrAl, TisAIN, or CuCrZr. The first material may comprise a refractory metal, such as titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium and rhenium, or a refractory metal alloy, such as Ti6A14V (titanium-aluminium-vanadium alloy); preferably, the first material comprises a refractory metal selected from tungsten, tantalum, molybdenum, titanium.

[0011] The second material may comprise a ceramic selected from the group of carbides, such as carbides of group IV-VI transition d-metals, optionally of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten; silicon carbide; metal oxides, such as aluminium oxide and zirconium oxide; metal nitrides; diamond; cubic boron nitride; or combinations thereof [0012] For example, the composite may be a tungsten-SiC composite, CuCrZr-SiC composite, EUROFER97-SiC composite, EUROFER97-WC composite, FeCrAl-WC composite, or Ti6A14VWC composite where WC is in the form of a cemented WC material. A cemented WC material as defined herein means a material made of WC grains bonded together by a binding agent, for example a metallic binder such as cobalt, iron, nickel, chromium or combinations thereof.

[0013] Typically, the first material is present in the composite in an amount to promote structural integrity and high fracture toughness. Typically, the composite is at least 5% by volume of the first material, preferably at least 10% by volume. The composite may be less than 30% by volume of the first material, preferably, less than 20 % by volume of the first material. The composite may be between 5 to 30% by volume of the first material, typically between 10 to 20% by volume.

[0014] Typically, the second material is present in the composite in an amount to provide high resistance to creep, thermal damage, high heat fluxes, plasma erosion, high resistance to neutron damage, high neutron shielding properties and high resistance to thermal cycling and fatigue. Typically, at least 70% by volume of the composite is the second material, preferably 80% by volume. The composite may be less than 95% by volume of the second material, typically, less than 90% by volume. The composite may be between 70 to 95% by volume of the second material, typically between 80 to 90% by volume.

[0015] The ratio of the second material to the first material may be in amounts of from about 19:1 to about 7:3, such as from about 4:1 to about 9:1.

[0016] The second material may further comprise a binder, such as a metallic binder. The metallic binder may be selected from cobalt, iron, nickel, chromium or combinations thereof.

[0017] The binder may be present in the second material in an amount of less than 15% by volume, preferably, in an amount of less than 5% by volume. The second material may comprise at least 85% by volume of ceramic particles, preferably, at least 95% by volume of ceramic particles.

[0018] Typically, the binder has a lower melting point than the ceramic of the second material. The binder may have a melting temperature of at least 1200°C.

[0019] According to another aspect, there is provided a method of manufacturing a composite for a first wall of a nuclear reactor, the method comprising: forming a first three-dimensional structure of a first material; filling the first three-dimensional structure with a second material to form a second three-dimensional structure interpenetrating the first three-dimensional structure, wherein the first material comprises a metal or metal alloy and the second material comprises a ceramic.

[0020] The metal three-dimensional structure may be formed first, prior to adding the ceramic second material. This may simplify the manufacturing method, because the metal is relatively easier to 3D print into intricate shapes and to high dimensional tolerances and may have a higher melting temperature than the binder used in the ceramic material and so it may be less complex to infiltrate the ceramic material into the metal structure than to infiltrate the metal into a ceramic structure.

[0021] Forming the first three-dimensional structure may comprise at least one of additive manufacturing or injection moulding the first material. The additive manufacturing may comprise at least one of 3D printing, selective laser sintering, roboc,asting and filling a sacrificial template with the first material in a powder form and pressing or sintering to form a rigid body then removing the sacrificial template. For example, the sacrificial template may be formed of wax and may be removed after the first three-dimensional structure is formed by melting the wax.

[0022] Filling the first three-dimensional structure with the second material may comprise filling the first three-dimensional structure with a powder or slurry of the second material and sintering the second material to form the second three-dimensional structure. Sintering the second material may comprise at least one of hot isostatic pressing (HIP), spark plasma sintering (SPS), pressure-less sintering and high-temperature and high-pressure sintering.

[0023] If the second material is in the form of a slurry, the method may further comprise a drying step to remove the moisture prior to the sintering step.

[0024] When a binding agent is present in the second material, ceramic particles are first mixed with the binder, such as cobalt, iron, nickel, chromium or combinations thereof The resulting mixture of the second material is then introduced to fill the cavities in the three-dimensional structure of the first material and the assembly is subjected to a sintering process.

[0025] The preparation of second material mixture (ceramic particles and binder) may involve high energy ball milling to coat the ceramic particles with the binder or other known mixing or coating processes to evenly distribute the binder around the particles or coat the particles with the binder.

[0026] The step of forming a first three-dimensional structure of a first material and the step of filling the first three-dimensional structure with a second material to form a second three-dimensional structure interpenetrating the first three-dimensional structure may take place simultaneously, so that the method is a single-step process. For example, the method may comprise 3D printing or 3D selective laser sintering a first material interpenetrating skeleton at the same time as the filling second material is 3D printed.

[0027] The metal and the ceramic may have similar melting/sintering temperatures, to allow the first and second structures to be 3D printed concurrently. The second material may comprise a metallic binder, and the melting temperature of the metal first material and the sintering temperature of the second material may be relatively similar, to allow the first and second structures to be 3D printed concurrently. For example, the first material may be Ti6A14\./ and the second material may be WC with a FeCr binder.

[0028] When the first and second materials are 3D printed concurrently the melting temperature of the first material is preferably within 200°C of the sintering temperature of the second material, more preferably, the melting temperature of the first material is within 100°C of the sintering temperature of the second material.

[0029] The first three-dimensional structure may comprise a plurality of cavities. Filling the first three-dimensional structure with the second material may comprise filling the cavities with the second material.

[0030] According to another aspect, there is provided a method of manufacturing a composite for a first wall of a nuclear reactor, the method comprising 3D printing first and second three-dimensional structures concurrently, wherein the structures are interpenetrating and wherein the first structure comprises a metal and the second structure comprises a ceramic.

[0031] As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts or percentages may be read as if prefaced by the word "about", even if the term does not expressly appear. The term "about" when used herein means +/-10% of the stated value. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. Singular encompasses plural and vice versa. For example, although reference is made herein to "a" porous ceramic member, "a" support member, "a" filter member, and the like, one or more of each of these and any other components can be used. As used herein, the term "polymer" refers to oligomers and both homopolymers and copolymers, and the prefix "poly" refers to two or more. Including, for example and like terms means including for example but not limited to. Additionally, although the present invention has been described in terms of "comprising", the processes, materials, and coating compositions detailed herein may also be described as "consisting essentially of' or "consisting of'.

[0032] Where ranges are provided in relation to a genus, each range may also apply additionally and independently to any one or more of the listed species of that genus.

[0033] All of the features contained herein may be combined with any of the above aspects in any combination.

[0034] Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0035] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: [0036] Figure 1 illustrates an example composite; [0037] Figure 2 illustrates a first structure of the composite of figure 1; [0038] Figure 3 illustrates another example composite; [0039] Figure 4 illustrates a first structure of the composite of figure 3; [0040] Figure 5 illustrates an example method of generating a composite; and [0041] Figure 6 illustrates another example method of generating a composite.

[0042] As shown in figure 1, an example composite 10 for forming a first wall of a nuclear reactor comprises a first structure 20 and a second structure 30. The first structure 20 is formed of a metal and the second structure 30 is formed of a ceramic. Figure 1 illustrates a plan view of the composite 10. The composite is a three-dimensional composite. Each of the first structure 20 and the second structure 30 individually forms a self-containing three-dimensional continuous network and the first and second structures are interpenetrating to form the composite. As shown in figure 1, the ceramic is present in a higher percentage by volume than the metal.

[0043] Figure 2 illustrates the first structure 20 in isolation. As shown in figure 2, the first structure 20 is a porous three-dimensional structure having a continuous three-dimensional pore network. The second structure is a three-dimensional structure which penetrates the pore network of the first structure 20 and comprises a pore network which is penetrated by the first structure, to form the three-dimensional interpenetrating phase composite 10.

[0044] Another example composite 110, shown in figure 3, comprises a first structure 120 and a second structure 130. The first structure 120 comprises a metal and the second structure 130 comprises a ceramic. As shown in figure 3, the ceramic is present in a higher percentage by volume than the metal.

[0045] Figure 4 illustrates the first structure 120 of the composite 110 in isolation. As shown in figure 4, the first structure is a porous three-dimensional structure having a continuous three-dimensional pore network. The second structure is a three-dimensional structure which penetrates the pore network of the first structure 120, to form the three-dimensional interpenetrating phase composite 110.

[0046] Figure 5 illustrates an example method 200 of forming a composite, such as the composite shown in figures 1 and 3. In step 210, a three-dimensional model of the first structure is generated, such as a CAD model.

[0047] In step 220, the first three-dimensional structure having open porosity is generated, such as the first structures shown in figures 2 and 4, according to the model generated in step 210.

The first structure may be generated by 3D printing, injection moulding, robocasting, or other moulding or casting methods. In some examples, the first structure may be generated by filling a sacrificial template with the first material in a powder form and pressing or sintering to form a rigid body then removing the sacrificial template.

[0048] In step 230, the first structure is infiltrated with a second material, such as a ceramics powder or slurry. The first structure is infiltrated with the second material to fill the pores of the first structure.

[0049] In step 240, the second material is subjected to a sintering process to fuse the particles of the second material, thereby solidifying the second material into a three-dimensional structure that penetrates the porous network of first structure whilst having a porous network that is penetrated by the first structure.

[0050] Figure 6 illustrates another example method 300 of forming a composite, such as the composite shown in figures 1 and 3 [0051] In step 310, a three-dimensional model of the composite is generated.

[0052] In step 320, the composite is generated. The composite is generated by generating the first structure and the second structure simultaneously, with the first structure and the second structure interpenetrating each other. For example, the composite may be generated by 3D printing or selective laser sintering, wherein the first and second materials are printed simultaneously to form the interpenetrating structure.

B

[0053] The first and second materials may have similar melting/sintering temperatures, to allow the first and second materials to be fused at the same time to form the first and second structures simultaneously. In an example, the second material may comprise for example a metallic binder, and the melting temperature first material and the sintering temperature of the second material may be relatively similar, to allow the first and second structures to be formed simultaneously.

[0054] Composites formed by the methods of figures 5 and 6 may advantageously combine properties of the first and second materials, without a trade-off between these properties. The fracture resistance and high thermal conductivity properties of the metal may be combined with the thermal and erosion resistance and neutron shielding properties of the ceramic to provide a first wall material having improved capability of withstanding the extreme operating conditions of a nuclear reactor. The interpenetrating structures of the first and second materials may improve the reliability of the first wall.

[0055] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0056] All the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0057] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0058] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A composite for forming a first wall of a fusion reactor, the composite comprising first and second materials that each have a continuous three-dimensional structure, wherein the structures of the first and second materials are interpenetrating, and wherein the first material comprises a metal and the second material comprises a ceramic.
2. A composite according to claim 1, wherein the first material has a melting temperature of at least 1200°C.
3. A composite according to claim1 or 2, wherein the second material has a melting temperature of at least 1200°C
4. A composite according to any preceding claim, wherein the first material comprises a metal or metal alloy selected from group IV-VIII metals.
5. A composite according to any preceding claim, wherein the first material comprises a refractory metal, such as titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium and rhenium, or a refractory metal alloy, such as steel, EUROFER97 (14%Cr oxide dispersion strengthened (ODS) steel), FeCrAl, TisAl4V, or CuCrZr.; preferably, wherein the first material comprises a refractory metal selected from tungsten, tantalum, molybdenum, titanium.
6. A composite according to any preceding claim, wherein the second material comprises a ceramic selected from the group of carbides, such as carbides of group IV-VI transition d-metals, optionally of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten; SIC; metal oxides, such as aluminium oxide and zirconium oxide; metal nitrides; diamond; cubic boron nitride; or combinations thereof
7. A composite according to any preceding claim, wherein the composite is a tungsten-SiC composite, CuCrZr-SiC composite, EUROFER97-SiC composite, EUROFER97 WC composite, FeCrAl-WC, or Ti5Al4V-WC composite, where WC is in the form of a cemented WC material.
8. A composite according to any preceding claim, wherein the first material is present in the composite in an amount of at least 5% by volume, preferably at least 10% by volume.
9. A composite according to any preceding claim, wherein the first material is present in the composite in an amount of less than 30% by volume, preferably less than 20% by volume.
10. A composite according to any preceding claim, wherein the second material is present in the composite in an amount of at least 70% by volume, preferably at least 80% by volume.
11. A composite according to any preceding claim, wherein the second material is present in the composite in an amount of less than 95% by volume, preferably, less than 90% by volume.
12. A method of manufacturing a composite for a first wall of a nuclear reactor, the method comprising: forming a first three-dimensional structure of a first material; filling the first three-dimensional structure with a second material to form a second three-dimensional structure interpenetrating the first three-dimensional structure, wherein the first material comprises a metal and the second material comprises a ceramic.
13. The method according to claim 12, wherein forming the first three-dimensional structure of the first material comprises at least one of injection moulding, 3D printing, robocasting, and filling a sacrificial template with the first material in a powder form and pressing or sintering to form a rigid body then removing the sacrificial template.
14. The method according to claim 1201 claim 13, wherein filling the first three-dimensional structure with the second material comprises filling the first three-dimensional structure with a powder or slurry of the second material and sintering the powder or slurry to form the second three-dimensional structure.
15. The method according to claim 12, wherein the filling the first three-dimensional structure with the second material comprises 3D printing the second three-dimensional structure at the same time as 3D printing the first three-dimensional structure.