Ceramic nuclear fuel dispersed in an alloy matrix.

Abstract

To provide a device and method of fabricating a metal-fuel-matrix cermet nuclear fuel.SOLUTION: A method of fabricating a metal-fuel-matrix cermet nuclear fuel may include the use of crushed ceramic particles combined with metallic fast reactor fuel via bottom pour casting or injection casting, or a powdered metallurgical process. A maximum quantity of the crushed ceramic particles added to a metallic fuel must not exceed that which would fail to yield a continuous matrix of metal fuel. After a short irradiation period, a microstructure of the fuel may be substantially identical to that of injection cast fuel, without the crushed ceramic particles, irrespective of a fabrication process.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to nuclear fuels, and in particular to metallic nuclear fuels. [Background technology]

[0002] World electricity demand is expected to double by 2030 and quadruple by 2050. The increase in world electricity demand is projected to come from developed countries and, to a significant extent, from developing countries. Nuclear power would be a viable and cost-effective energy source to meet this rapid increase in demand.

[0003] Increasing energy supplies from other sources, such as contributions from natural gas electricity generation, will be constrained by concerns about high and volatile gas prices, greenhouse gas emissions, and long-term dependence on unstable sources. Meanwhile, alternative forms of energy (such as solar, wind, biomass, and hydroelectric) may be useful in meeting some of the growing demand. But they will not grow fast enough to provide enough additional electricity generating capacity in most markets to meet any significant portion of the new electricity demand.

[0004] Coal power plants would provide some additional supply, but burning large amounts of coal poses significant political obstacles given its adverse environmental impacts. Conventional nuclear power plants could meet some of the additional demand, but they entail many technical and public acceptance hurdles to overcome. New types of nuclear fuel would also be required.

[0005] A power plant based on a specific fast reactor may have a 20-year fuel replacement interval maintained by a closed fuel cycle based on pyro-metallurgical recycling technology. For the initial core loading, an alloy fuel in the form of a uranium (U) / plutonium (Pu) / zirconium (Zr) composition or a enriched U / Zr composition can be used. (Fuel rods) To manufacture fuel pins, a remote injection casting process can be used. There is an extremely wide range of irradiation data bases for the steady state, transient and safety performance of the fuel. Recycled pins of ternary alloys can be highly radioactive, and the technology of using remote operation behind shielding at temperatures of 1500 - 1600 °C for their manufacture is well established.

Summary of the Invention

[0006] Aspects of the present invention will include a method for manufacturing a metal nuclear fuel incorporating ceramic particles. In certain aspects, the ceramic particles can include crushed light water reactor (LWR) spent nuclear fuel (SNF). In certain aspects, the ceramic particles can include thorium oxide and / or americium oxide. In certain aspects, materials from spent reactor fuel can be added to an alloy mixture. For example, ceramic particles such as LWR spent nuclear fuel can be crushed and dispersed in the matrix of the alloy.

[0007] U.S. Patent No. 8,571,167, U.S. Patent Application Publication No. 2011 / 019466 No. 6, and U.S. Patent Application Publication No. 2011 / 0206173 are each incorporated herein by reference in their entirety.

[0008] In certain aspects, the LWR-SNF particles of ceramic oxides can be combined with a metal fast reactor fuel by any one of the following three processes: ​1. Bottom pour casting fuel slug. An annular (or cylindrical) fuel slug. SNF fuel particles can be added to the molten metal fuel charge prior to bottom pour casting of the slug. The charge can be inductively heated using dual frequencies, and the change in frequency will result in mixing of the SNF particles in the melt. 2. Injection casting of solid fuel slugs. Solid, cylindrical fuel slugs. The SNF fuel particles can be added to the molten metal fuel charge prior to injection casting. The charge would be heated as described in 1. 3. Powder metallurgy processes. Metallic fuel particles produced by powder metallurgy processes can be combined (mixed) with SNF fuel particles.

[0009] The maximum amount of SNF fuel particles that can be added to the metallic fuel must be an amount that results in a continuous matrix of metallic fuel. Regardless of which manufacturing process is used, after brief irradiation, the fuel microstructure can be made identical, substantially identical, and / or functionally identical to the microstructure of injection cast fuel without the milled ceramic particles. Thus, an extensive database of injection cast fuel without the SNF particles would provide a good guide to expected irradiation throughput.

[0010] The process details and attributes of each process for producing fuel rods are described below. Each process contributes to solving the SNF problem by burning off the transuranium elements over multiple recycles, and all of them will denature Pu239 in the process. In certain embodiments, fuel rods can be produced using reprocessed metal fuel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Bottom pouring casting In certain devices, a bottom-pouring casting technique can be used to manufacture slugs for insertion into steel-clad fuel pins. The slugs can be annular zirconium (Zr) sheathed slugs. Upon irradiation, the as-manufactured pins can be rapidly reconstructed into the traditional morphology generated by the original injection casting manufacturing process, such that the existing extensive performance database for such fuel pins continues to apply.

[0012] The following description relates to typical embodiments for manufacturing annular fuel pins, but it should be understood that bottom-pouring casting can be used to manufacture any of a variety of fuel pins, including cylindrical or other shaped fuel pins.

[0013] The raw materials for the annular fuel pins can be charged into a bottom-pouring crucible and melted in an induction furnace. The melting time, temperature, pressure, and other operating conditions can be selected based on the raw materials to be introduced. The raw materials can be selected such that the desired composition for molybdenum (Mo) and / or zirconium (Zr) is obtained in addition to metallic uranium (U) and transuranic elements. In certain embodiments, the raw materials include, for example, uranium, zirconium, transuranic elements, reprocessed metallic fuel, and combinations thereof. In certain embodiments, a preformed thin-walled zirconium tube can be inserted to fit snugly into a hole that is press-fitted in a graphite mold. A rod can be placed at the center of the hole in the graphite mold. When the plug at the bottom of the crucible is raised, the molten alloy will flow into the mold and solidify.

[0014] In this way, in certain embodiments, slugs of annular fuel pins surrounded by a Zr coating in the radial direction can be manufactured. The slugs of the annular fuel pins can be removed from the mold and inserted into a press-fitted steel clad. End caps can be welded. Bundles of such pins can be assembled into a fuel assembly of multiple pins ​ It can be made into a body.

[0015] In certain embodiments, a feedstock of crushed ceramic particles can be added to the melt after the metal melt is in a molten state. The frequency of the induction furnace can be adjusted to create a turbulent rolling flow regime of the molten metal. This will help to mix the ceramic particles uniformly into the molten metal phase. Induction heating of U / Plutonium (Pu) / Zirconium (Zr) and Uranium (U) / Zr is known from current injection casting processes, and it is also known that a turbulent flow regime can be created by adjusting the frequency.

[0016] After a period of time, the agitation can be stopped. The length of time for agitation can be selected to achieve uniform or near-uniform mixing of the mixture. Underpouring can be performed as described above.

[0017] Freezing the mixture (preferably rapidly) will prevent resegregation of the relatively low density ceramic from the metallic phase. The time and temperature of cooling can be selected to prevent resegregation.

[0018] The resulting fuel slug will be a Zr-sheathed annular slug of cermet composition, with the fissile alloy forming a continuous matrix, with the majority of the fissile mass present as metallic phase. The ratio of metal fuel to ceramic can be selected such that upon irradiation, the fuel pin will produce a continuous matrix of metal fuel, thereby ensuring sufficient thermal conductivity. In certain embodiments, the dispersed ceramic particles will have a composition of greater than about 90% uranium oxide, about 6% fission products, and about 1.5% transuranium elements. These casting operations can be performed remotely, which is typically required when manufacturing with light water reactor spent nuclear fuel.

[0019] There are many potential operational advantages to annular fuel compacts, and providing the ability to manage spent nuclear fuel would provide further benefits. Injection casting In certain installations, known injection casting techniques have been used to produce solid (i.e., non-annular) slugs for insertion into steel clad fuel pins. The slugs can be solid fuel slugs that are inserted into a loose fit steel cladding and sodium, and are bonded to the sodium to provide good thermal conductivity between the slug and the cladding. Upon irradiation, the as-fabricated pins can be rapidly reconstructed into conventional fission gas filled porous configurations produced by the injection casting manufacturing process, to which an extensive current performance database is applied.

[0020] In certain embodiments, the injection casting process can be modified to incorporate ceramic particulates, such as crushed light water reactor spent nuclear fuel, into metal fuel pins. The raw materials for the fuel pins can be loaded into a crucible and melted in an induction furnace. The raw materials can be selected to obtain the desired composition of metallic uranium (U), transuranium elements, and / or zirconium (Zr).

[0021] In certain embodiments, a feedstock of crushed ceramic particles can be added to the melt after the metal melt is in a molten state. The frequency of the induction furnace can be adjusted to create a turbulent flow regime of the molten metal. The turbulent flow regime creates ceramic particles within the metal phase. This will help the particles mix evenly.

[0022] After a period of time, the agitation can be stopped. The length of time for agitation can be selected to achieve uniform or near uniform mixing of the mixture. An injection molding process can be performed to force the melt into a mold.

[0023] Cooling (preferably rapid cooling) of the mixture in the mold will prevent resegregation of the relatively low density ceramic from the metallic phase. The time and temperature of cooling can be selected to prevent resegregation.

[0024] The resulting fuel slug is a solid fuel pin of cermet composition, with approximately 50% by volume of fissile bearing metal matrix, and most of the fissile material is The metal fuel will be present as a metallic phase. The ratio of metal fuel to ceramic can be selected such that upon irradiation, the fuel pin will produce a continuous matrix of metal fuel (permeated with fission gases) to ensure sufficient thermal conductivity. In certain embodiments, the dispersed ceramic particles will have a composition of greater than about 90% uranium oxide, about 6% fission products, and about 1.5% transuranium elements. These injection casting operations can be performed remotely, which is typically required when manufacturing with light water reactor spent nuclear fuel.

[0025] Powdered fuel metallurgy Powder metallurgy facilitates the production of cermet fuel compositions, whereby ceramic particles can be embedded in a matrix of metallic phases. This capability, as well as the production methods of cermet fuel pins by bottom pouring and injection casting, allows the selection of crushed ceramic fuels, such as LWR spent fuel, and the introduction of crushed ceramic fuels into the closed fuel cycle that sustains fast reactor-based power plants. This would provide an effective solution for dealing with the difficult LWR spent fuel disposal problem. By limiting the volume fraction of the ceramic phase, it would be possible to maintain the applicability of previous fuel performance databases.

[0026] Fuel characteristics In all three embodiments, there will be a range of ceramic volume fractions that must be ensured in order to maintain applicability of previous databases on metallic fuel, maintain acceptable thermal conductivity ranges, and achieve the required level of fissile density. For the initial fuel charge of r, the volume fraction of ceramic will be such that there is a continuous metal matrix. For the U / Pu / Zr recycled fuel charge, the weight fraction of ceramic will be approximately 10 wt.% (this is just enough to recover the weight fraction of the burned heavy metals).

[0027] Established methods are known for comminution of LWR spent fuel, capture of released gaseous fission products, and tailoring of particle size distribution. Particle size may average between about 1 micron and about 100 microns. Uniform distribution of ceramic particles within the as-cast pin may be a relevant consideration for the present disclosure.

[0028] Regarding wetting, fuels manufactured by the current injection casting manufacturing process Small amounts of ceramic contamination from impurities have been found in the pins in the past. Wetting could be achieved by these processes.

[0029] Regarding particle agglomeration, even if ceramic particle agglomeration occurs during manufacturing, a certain degree of agglomeration will not significantly degrade the core performance. Since the enrichment of the fuel particles is about 1-2%, while the enrichment in the metal matrix would be greater than about 10%, the formation of "hot spots" of high fission density in the fuel due to particle agglomeration is not possible. Agglomeration may result in the formation of local "cool spots", but this does not pose a performance problem. Even if the manufacturing process never results in perfect homogeneity, there will be no hot spot problems.

[0030] Furthermore, the swelling of the core will not result in particle agglomeration. During the initial 1-1.5% of the core burnup, tiny bubbles of fission gas will form and the matrix of ductile metallic phase will fill the free volume of about 25%. The free volume is an annular volume. The ceramic particles are present in the central hole for the SUS304 pins, in the gap between the fuel slug and the cladding for the injection cast pins, and in the open porosity for the powder metallurgically produced fuel. The flow of the metal matrix will entrain the embedded ceramic particles, thereby increasing the average separation distance between the particles. Agglomeration will not be induced.

[0031] The ceramic particles will be primarily U238. U238 can be responsible for negative Doppler reactivity feedback during power-up transients. In some reactor configurations, the thermal time constant of the low thermal conductivity ceramic particles will prevent the rapidity of the negative reactivity feedback. However, its effect on other types of fast reactor transient performance will be negligible for several reasons. First, Doppler will not be the dominant reactivity feedback in (small) fast reactors. Instead, radial thermal expansion will dominate. Second, in the recycle charge, more than about 80% of the U238 (more than about 65% of the U238 in the initial fuel charge) will be present in the matrix of the metallic phase of the cermet fuel, in which case the heating will be instantaneous or near instantaneous. The rapid feedback from the metallic phase will dominate over the slightly delayed feedback from the ceramic phase. In addition, the ceramic particles will be very small, from about one micron to about several hundred microns, and will be well bonded to the surrounding metallic phase. Therefore, the thermal time delay of the ceramic particles will be very small.

[0032] Safeguards and the Benefits of Nuclear Non-Proliferation The introduction of crushed LWR spent fuel particles into the alloy fuel pins would have a nuclear non-proliferation benefit. This benefit would be especially advantageous for the initial core charge, where the uranium is enriched below 20% and does not contain any transuranic elements (which are non-radioactive in themselves). For the initial core, after irradiation, the resulting fuel composition will contain plutonium enriched in Pu239, but without substantial contamination with Pu240 and Pu241, while the recycled core, on the other hand, will form a mixture of plutonium isotopes that are unattractive for weapons use. Therefore, the initial charge of crushed LWR-SNF The addition of 1,2-dichloro-1,3-triphenylphosphine (DPPC) can provide several nonproliferation benefits.

[0033] First, oxide particles from pulverized LWR spent fuel contain fission products that provide a self-protecting radiation field for the initial core charge, which is initially a non-radioactive alloy-enriched uranium / Zr fresh fuel. It is not protected by the radiation field during its journey to the reactor.

[0034] Importantly, the ceramic particles can contain the isotopes Pu240 and Pu241. The particle size will be small enough, and the temperature of the fuel high enough, that significant migration of the isotopes occurs across all particle-matrix interfaces when bombarded with radiation in a nuclear reactor. Thus, Pu240 and Pu241 atoms can enter the metal matrix and intimately mix with the newly grown Pu239 in the metal matrix, and vice versa. (Any oxygen that migrates into the metal phase is converted to Z.) r). Thus, the newly bred Pu-239 would become contaminated with Pu-240 and Pu-241 after only a short exposure in a nuclear reactor, which would make it unattractive for use in a nuclear weapon.

[0035] The "modification" of the initial core load with Pu240 and Pu241 may be important because in that initial load the volume fraction of ceramics approaches about 50% and the weight fraction of heavy metals is about 35%. In LWR spent fuel, the weight fraction of plutonium is about 1.5%, and the weight fraction of plutonium and the (240+241) / (239+240+241) isotopic contamination of Pu239 is about 40%, whereas the corresponding asymptotic composition in a fast reactor obtained after multiple recycles would be about 25%.

[0036] After an initial 20-year irradiation period achieving approximately 8 atomic percent burnup, the initial fuel charge will have progressed approximately 10% of the way through the fissile composition, with all of the fissile composition being U235 to Pu. The Pu239 composition will have progressed from being 239-enriched to an asymptotic (240+241) contamination of Pu239.

[0037] After the first 20-year irradiation period, the initial fuel charge in the metallic phase is reduced by, for example, (100-35 wt.% fuel) x (fuel) to the breeding charge of Pu239 atoms in the fuel. (13% by weight of fissile material in the u) = 0.00845.

[0038] The ceramic may be, for example, (35 wt. % fuel) x (1.5% Pu in fuel) x (Pu) for a charge of (240 + 241) atoms for each atom of Pu in the fuel. The contribution of 40% of the total would be 240 + 241) = 0.00845.

[0039] Therefore, if perfect mixing occurs, the (240 + 241) / The ratio of (239+240+241), for example, is approximately (0.0021) / (0.008 45+0.0021)=0.199, which may be considered as an asymptotic value already modified. The mixing of isotopes can be achieved by considering the temperature and temperature gradient of the fuel pin, the strong radiation field, and the duration of exposure to these conditions. The migration of isotopes across the ceramic-metal interface will result in homogeneous mixing with the proliferated Pu239. Thus, a significant substantial modification will be obtained even for the first fuel charge. The effect will be less for the recycled fuel charge, because the ceramic weight fraction will drop to about 8-10 wt%, but by that time the Pu will already be modified and the recycled fuel can be loaded with the radioactive fission products retained in the recycling process.

[0040] It should be noted that the above description is directed to the preferred embodiment of the present invention, but other variations and modifications are obvious to those skilled in the art and can be made without departing from the spirit or scope of the present invention. Furthermore, even if not expressly stated above, an embodiment described with respect to one embodiment of the present invention can be used in combination with other embodiments. The following is a transcription of the claims as of the filing of this application. [1] A method for manufacturing a cermet metal fuel matrix nuclear fuel pin, comprising the steps of: melting one or more metallic nuclear fuel sources, thereby forming a molten metal melt; adding ceramic particles into a melt of molten metal, thereby forming a mixture; Stir the mixture vigorously; pouring the mixture into a mold; and allowing the mixture to solidify in the mold, thereby forming a cermet metal fuel matrix nuclear fuel pin; The method comprising: [2] The method of [1], wherein the stirring comprises turbulence of the mixture to thereby achieve a substantially uniform distribution of the particles. [3] The method according to [1], wherein the ceramic particles include pulverized light water reactor spent nuclear fuel, thorium oxide, americium oxide, and combinations thereof. [4] The method of [1], wherein the ceramic particles include thorium oxide, americium oxide, and combinations thereof. [5] The method according to [1], wherein the mold has a cylindrical hole and the rod is located approximately at the center of the cylindrical hole. [6] The method according to [5], wherein the obtained cermet metal fuel matrix nuclear fuel pin is an annular cermet metal fuel matrix nuclear fuel pin. [7] The method of [1], wherein the mold includes one or more zirconium tubes fitted within cavities in the mold. [8] The method according to [7], wherein the resulting fuel pin is a zirconium sheathed cermet metal fuel matrix nuclear fuel pin. [9] The method described in [1], wherein the distribution of ceramic particles within the cermet metal fuel matrix remains uniform even after the mixture is solidified by rapid cooling.

[10] The method of [1], wherein the one or more metallic nuclear fuel sources include uranium.

[11] The method of [1], wherein the one or more metallic nuclear fuel sources comprise (i) uranium, and (ii) zirconium or molybdenum.

[12] The method of [1], wherein the one or more metallic nuclear fuel sources comprise a mixture of uranium and transuranium elements.

[13] A method for manufacturing a cermet metal fuel matrix nuclear fuel pin, comprising the steps of: melting one or more metallic nuclear fuel sources, thereby forming a molten metal melt; adding ceramic particles into a melt of molten metal, thereby forming a mixture; Stir the mixture vigorously; injection casting the mixture into a mold; and allowing the mixture to solidify in the mold, thereby forming a cermet metal fuel matrix nuclear fuel pin; The method comprising:

[14] The method of

[13] , wherein the stirring comprises agitating the molten metal melt to thereby achieve uniform mixing of the ceramic particles within the molten metal melt.

[15] The method of

[13] , wherein the crushed ceramic particles comprise light water reactor spent nuclear fuel.

[16] The method of

[13] , wherein the ground ceramic particles comprise thorium oxide.

[17] The method of

[13] , wherein solidifying the mixture is by cooling.

[18] The method of

[13] , wherein the one or more metallic nuclear fuel sources include uranium.

[19] The method of

[13] , wherein the one or more metallic nuclear fuel sources include uranium and zirconium.

[20] The method of

[13] , wherein the one or more metallic nuclear fuel sources comprise a mixture of uranium and transuranium elements.

[21] A method for manufacturing metal nuclear fuel pins, comprising the steps of: adding granular metallic nuclear fuel material; Adding ceramic particles to granular metallic nuclear fuel feedstock; mixing the pulverized ceramic particles with a granular metallic nuclear fuel feedstock, thereby forming a homogeneous mixture; and pouring the mixture into a steel sheath and allowing it to harden; The method comprising:

[22] The method of

[21] , wherein the ceramic particles include pulverized light water reactor spent nuclear fuel.

[23] The method of

[21] , wherein the milled ceramic particles include thorium oxide, americium oxide, and combinations thereof.

[24] The method of

[21] , wherein the one or more metallic nuclear fuel sources comprise particles of uranium.

[25] The method of

[21] , wherein the one or more metallic nuclear fuel sources comprise particles of uranium and zirconium.

[26] The method of

[21] , wherein the one or more metallic nuclear fuel sources comprise a mixture of particles of uranium and transuranium elements.

Claims

1. 1. A method for manufacturing a cermet metal fuel matrix nuclear fuel pin, comprising the steps of: melting one or more metallic nuclear fuel feedstocks in an induction furnace to form a molten metal melt; grinding the ceramic particles; adding ground ceramic particles into a melt of molten metal to form a mixture; agitating the mixture; pouring the mixture into a mold; forming a cermet metal fuel matrix nuclear fuel pin by solidifying the mixture in a mold; Including, The method of claim 1, wherein the ceramic particles have a composition including greater than 90% uranium oxide, 6% fission products, and 1.5% transuranium elements.

2. The method of claim 1 , wherein the stirring comprises adjusting a frequency of the induction furnace to agitate the mixture to produce a uniform distribution of particles.

3. The method of claim 1 , wherein the crushed ceramic particles comprise light water reactor spent nuclear fuel.

4. The method of claim 1 , wherein the mold has a cylindrical bore with a rod approximately in the center of the cylindrical bore.

5. 5. The method of claim 4, wherein the resulting cermet metal fuel matrix nuclear fuel pin has an annular or cylindrical shape.

6. The method of claim 1 , wherein solidifying the mixture is accomplished by cooling.

7. The method of claim 1 , wherein the mold includes one or more zirconium tubes fitted within holes in the mold.

8. 8. The method of claim 7, wherein the resulting fuel pin is a zirconium sheathed cermet metal fuel matrix nuclear fuel pin.

9. The method of claim 1 , wherein the one or more metallic nuclear fuel sources comprise uranium.

10. The method of claim 1 , wherein the one or more metallic nuclear fuel sources include uranium and zirconium.

11. The method of claim 1 , wherein the one or more metallic nuclear fuel sources include uranium and transuranium elements.