Manufacturing method for metallic fuel containing minor actinoid
The method of evaluating and mixing minor actinoids and other fuel materials to form metal fuels addresses the challenge of maintaining low fission product concentrations without electrolytic purification, resulting in cost-effective and efficient metal fuel production.
Patent Information
- Application Number
- JP2023166059
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-09-27
- Publication Date
- 2025-04-08
AI Technical Summary
The existing methods for producing metal fuels for fast reactors require additional steps like electrolytic purification to keep fission products below the standard value of 0.3 wt%, which increases time and financial costs.
A method is developed to produce metal fuels by evaluating the composition of minor actinoids and other fuel materials, calculating the optimal mixing ratio to achieve a concentration of minor actinoids around 5% and fission products below 0.3 wt%, and then mixing and melting these components to form an alloy for the metal fuel.
This method allows for the production of metal fuels with fission products kept below the standard value without the need for electrolytic purification, thereby reducing production time and costs.
Smart Images
Figure 2025056528000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for producing metallic fuel containing minor actinides, among metallic fuels used in fast reactors. [Background technology]
[0002] Fast reactors are being developed as the nuclear reactors of the future. Unlike the light water reactors currently used in nuclear power generation, fast reactors have the advantage of being able to breed plutonium (Pu) and easily transmuting (destroying) minor actinides (MA), which are long-lived radioactive nuclides contained in spent fuel.
[0003] As fuel for fast reactors, in addition to the same oxide fuel as that used in light water reactors, metallic fuel containing minor actinides (hereinafter referred to as metallic fuel) is also being considered for disposal of minor actinides. A representative metallic fuel under consideration is one that combines uranium (U) and plutonium with minor actinides and zirconium (Zr), and research and development of technology to recover minor actinides from spent fuel is underway.
[0004] It is known that when minor actinides are recovered from spent fuel, they are accompanied by fission products (FPs). Since fission products are impurities that do not contribute to nuclear reactions, when obtaining metallic fuel from spent fuel, a method is used in which the fission products are removed to below a standard level to obtain the nuclear fuel material in its metallic chemical form, and then the material is processed into metallic fuel.
[0005] Various studies have been conducted on the concentration of fission products in metallic fuel. For example, Non-Patent Document 1 states that the required specifications for fuel require that the concentration of fission products in the fuel be 0.3 wt% or less. [Prior art documents] [Non-patent literature]
[0006] [Non-Patent Document 1] Kensuke Kinoshita et al., "Mass Balance Assessment and Plant Conceptual Design of Metal Fuel Dry Reprocessing Process", Report of the Central Research Institute of the Electric Power Industry, Central Research Institute of the Electric Power Industry, July 2012, Research Report: L11009, p.4 Summary of the Invention [Problem to be solved by the invention]
[0007] Various types of fuel are used in light water reactors in Japan, and therefore various types of spent fuel are generated. The concentration of fission products associated with minor actinides varies depending on the spent fuel. Therefore, if the concentration of fission products in metallic fuel exceeds the aforementioned standard value of 0.3 wt%, the concentration of fission products must be reduced below that standard value.
[0008] One method to reduce the concentration of fission products is to remove them using electrolytic refining, as described in Non-Patent Document 1, but adding this process increases the time and financial costs required to manufacture metallic fuel.
[0009] An object of the present invention is to provide a method for producing metallic fuel containing minor actinides, in which fission products are suppressed to below standard values without using a fission product removal process such as electrolytic refining. [Means for solving the problem]
[0010] The present application includes a number of means for solving the above-mentioned problems, and one example thereof is a method for producing metallic fuel containing a minor actinide, comprising: evaluating the composition of at least one raw material that is a raw material for the metallic fuel and contains a minor actinide; calculating, by reference to the composition, a mixing ratio of at least one metallic minor actinide obtained by metal conversion of each of the at least one raw material and other fuel materials so that the concentration of fission products in the metallic fuel is below a reference value and the concentration of minor actinides in the metallic fuel is a desired value; and mixing and melting the at least one metallic minor actinide and the other fuel materials based on the mixing ratio to obtain an alloy, which is used as the metallic fuel. Effect of the Invention
[0011] According to the present invention, it is possible to manufacture metallic fuel in which fission products are suppressed to below the standard value without using a fission product removal process such as electrolytic refining. Other problems, configurations, and effects will become clear from the description of the following embodiments. [Brief description of the drawings]
[0012] [Figure 1] 1 is a table showing an example of the concentrations of minor actinides and fission products contained in spent fuel. [Diagram 2] 1 is a table showing an example of the ratio of fission products contained in minor actinides recovered from spent fuel. [Diagram 3] 1 is a table showing an example of concentrations of fission products contained in metallic fuel containing minor actinides at predetermined concentrations recovered from spent fuel. [Figure 4] 1 is a flowchart of a method for producing metallic fuel according to a first embodiment of the present invention. [Diagram 5] 10 is a flowchart of a method for producing metallic fuel according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The present invention relates to a method for producing metallic fuel.
[0014] Minor actinides is a general term for the nine actinide elements contained in spent nuclear fuel, excluding uranium and plutonium: neptunium (Np), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr).
[0015] Minor actinides contain isotopes that are highly radiotoxic and have extremely long half-lives. Because it is difficult to recycle them together with plutonium in light water reactors, which are currently the mainstream power reactors, there are plans to separate them during the reprocessing process and dispose of them in a geological repository.
[0016] On the other hand, in fast reactors, these minor actinides are mixed into the fuel in a certain amount and eliminated through burning (nuclear fission) and conversion reactions, which makes it possible to suppress the increase in the minor actinides in the fuel cycle system. For this reason, methods for manufacturing metallic fuel for use in fast reactors are being considered.
[0017] There are several methods for producing metallic fuel. For example, there is a method for producing metallic fuel from nuclear fuel material that has had impurities removed using dry reprocessing, in which spent fuel is reprocessed in a gaseous, powdered, or molten state. There is also a method for producing metallic fuel from oxide nuclear fuel material that has been recovered using wet reprocessing, in which spent fuel is reprocessed using an aqueous solution of nitric acid, and then converted into metal.
[0018] In both manufacturing methods, nuclear fuel material is obtained in the chemical form of metal after removing fission products, which are nuclides produced during the nuclear fission process, and then processed into metallic fuel.
[0019] Concerning the concentration of minor actinides in metallic fuel, a fairly wide range of concentrations has been considered, and the inventors have considered a minor actinide concentration of about 5% as a representative example.
[0020] In addition, various studies have been conducted on the concentration of fission products remaining in metallic fuel. For example, there are studies that suggest that it is desirable to keep the concentration of fission products below 0.3 wt%.
[0021] Therefore, in this embodiment, a method for manufacturing metallic fuel was studied by setting the desired concentration of minor actinides to about 5%, and the reference value for the concentration of fission products to 0.3 wt% or less.
[0022] Currently, in Japan, efforts are underway to commercialize wet reprocessing using the Purex method, a solution extraction method for the reprocessing of spent nuclear fuel that extracts only uranium and plutonium into an organic phase and leaves fission products in the aqueous phase. Research and development is also underway to separate minor actinides using wet methods.
[0023] The inventors considered that, when metallic fuel is introduced into the country, it would be better from the viewpoint of the consistency of the domestic nuclear fuel cycle to first use nuclear fuel material recovered by wet reprocessing as a raw material and convert its chemical form into a metal before using it as metallic fuel. In this case, they considered that in the future, when separation of minor actinides by wet methods is put to practical use in addition to wet reprocessing of nuclear fuel material, minor actinides will also be converted into metals, as with nuclear fuel material, before being added to metallic fuel.
[0024] In addition to power generation using light water reactors fueled by uranium, Japan is promoting plu-thermal power generation using MOX fuel, a mixed oxide of uranium and plutonium. As a result, various types of fuel, including uranium and MOX fuel, are used in Japan, and various types of spent fuel are generated.
[0025] Against this background, when considering a method for producing metallic fuel, the inventors considered that the composition of the minor actinides recovered would differ depending on the type of spent fuel, and came up with the idea of evaluating the composition of the minor actinides recovered from different spent fuels and calculating the mixing ratio of metallic minor actinides to other fuel materials before producing metallic fuel.
[0026] Figure 1 is a table showing an example of the concentrations of minor actinides and fission products contained in spent fuel. Figure 2 is a table showing an example of the ratio of fission products contained in minor actinides recovered from spent fuel.
[0027] As shown in Figures 1 and 2, spent uranium fuel and spent MOX fuel are used as spent fuel, and minor actinides are separated from the spent fuel after wet reprocessing.
[0028] In addition, because the decontamination coefficient, which indicates the degree to which the recovered uranium and plutonium is removed by the decontamination process in reprocessing using the Purex method, is very high, it was assumed that no fission products would accompany the uranium and plutonium recovered from spent fuel.
[0029] In addition, the separation performance of minor actinides was based on research results, and the recovery rate of minor actinides recovered from spent fuel was assumed to be 99.9%, and the removal rate of fission products removed from spent fuel was assumed to be 99%. It was also assumed that the recovered minor actinides would be accompanied by 1% of fission products that cannot be removed from the spent fuel.
[0030] When the ratio of fission products contained in the minor actinides recovered under these conditions was evaluated, the ratio was 0.071 for spent uranium fuel and 0.017 for spent MOX fuel, as shown in Figure 2. This indicates that the amount of fission products associated with the minor actinides recovered from spent uranium fuel was greater than the amount of fission products associated with the minor actinides recovered from spent MOX fuel.
[0031] FIG. 3 is a table showing an example of the concentrations of fission products contained in metallic fuel containing a specified concentration of minor actinides recovered from spent fuel.
[0032] As mentioned above, it is assumed that fission products are not associated with the uranium and plutonium recovered from the spent fuel, but only with the minor actinides recovered from the spent fuel. Therefore, the concentration of fission products in metallic fuel made from metallic minor actinides recovered from the spent fuel is proportional to the concentration of minor actinides in the metallic fuel.
[0033] The concentration of fission products contained in metallic fuel recovered from spent uranium fuel is, for example, 0.36 wt% when the concentration of minor actinides is 5% and 0.21% when it is 3 wt%, as shown in Figure 3. On the other hand, the concentration of fission products contained in metallic fuel recovered from spent MOX fuel is 0.09 wt% when the concentration of minor actinides is 5% and 0.05% when it is 3 wt%.
[0034] Of these cases, only when the concentration of minor actinides in the metallic fuel recovered from spent uranium fuel is 5%, does it not meet the fission product concentration standard of 0.3 wt% or less. In this case, the concentration of fission products needs to be reduced.
[0035] Thus, depending on the type of spent fuel and the concentration of minor actinides contained in the metallic fuel, there are cases where the fission product concentration meets the standard value of 0.3 wt% or less and cases where it does not.
[0036] Methods for reducing the concentration of fission products include removing them by electrolytic refining or other methods. When there is a large amount of fission products associated with minor actinides, it is possible to reduce the concentration of fission products by removing them by electrolytic refining or other methods before producing metallic fuel.
[0037] However, the inventors considered that a method of producing metallic fuel without additionally removing fission products by electrolytic refining or the like would be desirable in order to set the concentration of fission products in metallic fuel obtained by mixing nuclear fuel material recovered from spent fuel by wet reprocessing and minor actinides recovered by minor actinide separation to a standard value.
[0038] The inventors then created the following method for manufacturing metallic fuel, in which the concentration of minor actinides is reduced to the desired value of about 5% and the concentration of fission products is reduced to the standard value of 0.3 wt% or less, by reducing the concentration of metallic minor actinides contained in the metallic fuel depending on the concentration of fission products in the metallic fuel, or by mixing minor actinides recovered from other spent fuel in a specified ratio.
[0039] This is a manufacturing method in which the composition of at least one spent fuel which is a raw material for metallic fuel and which contains a minor actinide is evaluated, a mixing ratio of at least one metallic minor actinide obtained by metal conversion of at least one raw material to other fuel materials is calculated by referring to the composition of the at least one raw material so that the concentration of fission products in the metallic fuel is below a reference value and the concentration of minor actinide in the metallic fuel is at a desired value, and the at least one metallic minor actinide is mixed with the other fuel materials based on the mixing ratio and melted to obtain an alloy, thereby producing metallic fuel.
[0040] This manufacturing method is a method for manufacturing metallic fuel that takes advantage of the fact that the ratio of fission products contained in minor actinides recovered from spent fuel, as shown in the table in Figure 2, is constant depending on the type of spent fuel.
[0041] Specifically, this is a production method that utilizes the fact that the concentration of fission products can be reduced by reducing the concentration of metallic minor actinides in metallic fuel, as shown in the table in Figure 3, and that the concentration of fission products can be reduced by mixing minor actinides recovered from spent uranium fuel with minor actinides recovered from spent MOX fuel.
[0042] More specifically, it is a manufacturing method that uses the following: The fission products contained in metallic fuel are fission products that accompany minor actinides recovered from spent fuel. Therefore, the concentrations of fission products and minor actinides are proportional. Also, the amount of fission products that accompany minor actinides varies depending on the type of spent fuel. The concentrations of fission products in metallic fuel mixed with minor actinides recovered from different spent fuels are equalized.
[0043] [effect] The method for manufacturing metallic fuel in this embodiment involves evaluating the composition of at least one spent fuel which is the raw material 10 for the metallic fuel and which contains a minor actinide, calculating a mixing ratio of at least one metallic minor actinide 11 obtained by metal conversion of at least one raw material 10 and other fuel material 12 by referring to the composition of at least one spent fuel so that the concentration of fission products in the metallic fuel 14 is below the standard value of 0.3 wt% and the concentration of minor actinides in the metallic fuel 14 is the desired value of around 5%, and mixing and melting the at least one metallic minor actinide 11 and the other fuel material 12 based on the mixing ratio to obtain an alloy 13 which is then used as metallic fuel 14.
[0044] This makes it possible to produce metallic fuel in which fission products are suppressed to below the standard value without using a fission product removal process such as electrolytic refining.
[0045] Hereinafter, the configurations and operations of the methods for producing metallic fuel according to the first and second embodiments of the present invention will be described with reference to the drawings. Note that in each drawing, the same reference numerals denote the same parts.
[0046] (First embodiment) FIG. 4 is a flowchart of a method for producing metallic fuel according to the first embodiment.
[0047] As shown in FIG. 1, the method for producing metallic fuel according to this embodiment includes a composition evaluation step S101, a metal conversion step S102, a mixture ratio calculation step S103, a mixing step S104, and an injection casting step S105.
[0048] The composition evaluation step S101 is a step of evaluating the composition of the metallic fuel raw material 10. In the composition evaluation step S101 of this embodiment, the composition of one raw material 10 is evaluated.
[0049] The raw material 10 is preferably minor actinides recovered from spent nuclear fuel such as spent uranium fuel or spent MOX fuel. Minor actinides recovered from spent nuclear fuel are accompanied by small amounts of fission products as impurities. Therefore, in the composition evaluation step S101, it is preferable to evaluate the concentration of minor actinides and the concentration of fission products in the raw material 10. The chemical form of the raw material 10 is preferably an oxide.
[0050] The composition is preferably evaluated from the composition of the spent fuel and the processing conditions of the chemical processing of the spent fuel. The evaluation based on the composition of the spent fuel is preferably an evaluation by calculation based on the composition of the fuel before use, the burnup of the fuel, and the combustion history of the fuel. The evaluation based on the processing conditions of the chemical processing is preferably an evaluation based on the processing conditions of the wet reprocessing for recovering uranium and plutonium, and the processing conditions for separating minor actinides from the spent fuel from which uranium and plutonium have been recovered by wet reprocessing. The composition may also be evaluated by chemical analysis of a portion of the raw material 10.
[0051] The metal conversion step S102 is a step in which the raw material 10 whose composition has been evaluated in the composition evaluation step S101 is converted into a metal by, for example, immersing it in a high-temperature chloride molten salt and electrolyzing it, thereby obtaining metallic minor actinides 11.
[0052] The mixing ratio calculation step S103 is a step of calculating, for example, by a calculation device, the mixing ratio of metallic minor actinides 11 and other fuel materials 12 based on the composition of the raw material 10 evaluated in the composition evaluation step S101, in order to set the concentration of minor actinides in the metallic fuel to a desired value of around 5% and the concentration of fission products in the metallic fuel to a reference value of 0.3 wt% or less. The other fuel materials 12 are preferably uranium, plutonium, and zirconium.
[0053] The mixing ratio calculation step S103 calculates a mixing ratio based on the composition data evaluated in the composition evaluation step S101, and outputs the calculated mixing ratio to the mixing step S104. Therefore, since the mixing ratio calculation step S103 is not a process for processing a substance like other processes, but a process for processing data, the data input to and output from the mixing ratio calculation step S103 is indicated by dotted lines in FIG.
[0054] The mixing step S104 is a step of producing an alloy 13 by mixing the metallic minor actinide 11 and the other fuel material 12 based on the mixing ratio calculated in the mixing ratio calculation step S103 and melting the mixture at a high temperature. The chemical form of the other fuel material 12 is preferably metallic. The uranium and plutonium may be recovered by reprocessing spent nuclear fuel.
[0055] The mixing ratio of metallic minor actinide 11 and other fuel material 12 in the mixing step S104 can be, for example, uranium:plutonium:minor actinide=75:20:5. It is also preferable to add zirconium, which is an additive for increasing the melting point, to the alloy 13 at 10 wt %. Note that metallic minor actinide 11 is accompanied by fission products as impurities, and therefore the alloy 13 produced in the mixing step S104 contains a small amount of fission products.
[0056] Here, when the metallic minor actinides 11 recovered from spent uranium fuel are mixed with other fuel materials 12 so that the concentration of metallic minor actinides 11 in the metallic fuel is 5%, the concentration of fission products contained in the metallic fuel 14 becomes 0.36 wt%, as shown in the table in Figure 3, which exceeds the standard value of 0.3 wt%.
[0057] In such a case, taking into consideration the composition of the raw material 10 evaluated in the composition evaluation step S101, a mixing ratio is calculated in the mixing ratio calculation step S103 such that the concentration of the fission products is equal to or less than the reference value of 0.3 wt%.
[0058] As shown in the table in Figure 3, if the concentration of metallic minor actinides in metallic fuel is reduced from 5% to 3%, the concentration of fission products will decrease from 0.36 wt% to 0.21 wt%, below the standard value of 0.3 wt%.
[0059] Therefore, in the mixing ratio calculation step S103 of this embodiment, the mixing ratio of the metallic minor actinides 11 and the other fuel materials 12 is calculated so that the concentration of the metallic minor actinides 11 satisfies the reference value of 0.3 wt % or less for the concentration of fission products.
[0060] Then, in a mixing step S104, the metallic minor actinide 11 and the other fuel material 12 are mixed according to the mixing ratio calculated in the mixing ratio calculation step S103.
[0061] In the injection casting process S105, the alloy 13 mixed in the mixing process S104 is melted and injected into a glass sheath tube to be cast into a rod shape, and then cooled to remove the metal fuel 14, which is a fuel slug, from the sheath tube.
[0062] Through these steps, metallic fuel can be produced from one raw material 10, with the concentration of minor actinides in the metallic fuel being the desired value of around 5% and the concentration of fission products being the standard value of 0.3 wt% or less.
[0063] The method for producing metallic fuel according to this embodiment has the following features.
[0064] In the method for producing metallic fuel according to the present embodiment, in a composition evaluation step S101 for evaluating the composition, the composition of one raw material, for example, a minor actinide recovered from spent uranium fuel, is evaluated. Then, in a mixing ratio calculation step S103 for calculating the mixing ratio, the mixing ratio of one metallic minor actinide 11 obtained by metal conversion of one raw material, for example, a minor actinide recovered from spent uranium fuel, in a metal conversion step S102, and other fuel materials 12 is calculated. Then, in a mixing step S104 for obtaining an alloy, the one metallic minor actinide 11 is mixed with the other fuel materials 12 based on the mixing ratio of the one metallic minor actinide 11 and the other fuel materials 12 calculated in the mixing ratio calculation step S103.
[0065] [effect] In the method for producing metallic fuel in this embodiment, in a composition evaluation step S101, the composition of one raw material 10 is evaluated, in a mixing ratio calculation step S103, the mixing ratio of one metallic minor actinide 11 obtained by metal conversion of one raw material 10 and other fuel materials 12 is calculated, and in an alloy obtaining step S104, the one metallic minor actinide 11 is mixed with the other fuel materials 12 based on the mixing ratio of the one metallic minor actinide 11 and the other fuel materials 12.
[0066] That is, the method for producing metallic fuel according to this embodiment is a method for producing metallic fuel using only one raw material, for example, minor actinides recovered from spent uranium fuel, as the raw material. When this minor actinide is mixed with metallic minor actinide 11 converted into metal in the metal conversion step S102 and other fuel material 12, the other fuel material 12, which is uranium, plutonium, and zirconium, contains almost no fission product components. Therefore, the fission products contained in the metallic fuel 14 are derived from the fission products contained in the metallic minor actinide 11.
[0067] The concentration of fission products contained in minor actinides recovered from spent uranium fuel can be calculated from the ratio of fission products contained in minor actinides recovered from spent fuel, 0.071, shown in the table in Figure 2. As a result, when the concentration of metallic minor actinides 11 in metallic fuel 14 is 5%, the concentration of fission products contained in metallic fuel 14 using minor actinides recovered from spent uranium fuel as raw material 10 is 0.36 wt%, as shown in the table in Figure 3.
[0068] Therefore, the concentration of the fission products in the metallic fuel 14 exceeds the reference value of 0.3 wt% or less. Therefore, in this embodiment, based on the composition evaluated in the composition evaluation step S101, the mixture ratio calculation step S103 calculates the mixture ratio when the concentration of the metallic minor actinide 11 in the metallic fuel 14 is changed to, for example, 3%. As a result, as shown in the table of Fig. 3, the concentration of the fission products becomes 0.21%, which can be made the reference value of 0.3 wt% or less.
[0069] That is, the mixing ratio calculation step S103 of this embodiment calculates the mixing ratio of metallic minor actinides 11 and other fuel materials 12 so that the concentration of fission products is equal to or less than the reference value of 0.3 wt% according to the composition of minor actinides, which is the metallic fuel raw material 10. This makes it possible to manufacture metallic fuel 14 in which the concentration of fission products is suppressed to the reference value of 0.3 wt% or less without additionally refining the raw material.
[0070] In the metallic fuel production method according to the present embodiment, the composition of the raw material 10 is evaluated from the composition of the spent fuel and the processing conditions of the chemical processing of the spent fuel in the composition evaluation step S101. This makes it possible to evaluate the composition of the raw material 10 without chemically analyzing a portion of the raw material 10.
[0071] Furthermore, in the metallic fuel manufacturing method according to this embodiment, the composition of the raw material 10 includes the concentration of minor actinides and the concentration of fission products in the raw material 10 in the composition evaluation step S101. This makes it possible to calculate the mixing ratio in the mixing ratio calculation step S103 so that the concentration of fission products in the metallic fuel 14 is equal to or less than the reference value of 0.3 wt% and the concentration of minor actinides in the metallic fuel 14 is the desired value of around 5%.
[0072] Second embodiment 5 is a flow chart of a method for producing metal fuel according to a second embodiment of the present invention. The method for producing metal fuel according to this embodiment differs from the method for producing metal fuel according to the first embodiment in the following points.
[0073] The manufacturing method for metallic fuel according to this embodiment differs from the manufacturing method for metallic fuel according to the first embodiment in that in a composition evaluation step S201, the compositions of a plurality of raw materials, for example, the raw material 10 recovered from spent uranium fuel and the raw material 210 recovered from spent MOX, are evaluated. Then, in a metal conversion step S202, the plurality of raw materials, for example, the raw material 10 recovered from spent uranium fuel and the raw material 210 recovered from spent MOX, are converted into metals.
[0074] Then, in a mixing ratio calculation step S203 for calculating the mixing ratio, the mixing ratio of each of a plurality of metallic minor actinides 11, 211 obtained by metal conversion of a plurality of raw materials, for example, raw material 10 recovered from spent uranium fuel and raw material 210 recovered from spent MOX, and other fuel materials 12 is calculated so that the concentration of fission products in the metallic fuel is equal to or less than the reference value of 0.3 wt% and the concentration of minor actinides in the metallic fuel is the desired value of around 5%.
[0075] Then, in a metallic minor actinide mixing step S204a, the multiple metallic minor actinides 11, 211 are mixed according to the mixing ratio calculated in the mixing ratio calculation step S203 to obtain a metallic minor actinide 311. Furthermore, in a mixing step S204 for obtaining an alloy, the metallic minor actinide 311 is mixed with other fuel materials 12 according to the mixing ratio calculated in the mixing ratio calculation step S203.
[0076] Furthermore, the method for producing metallic fuel according to the first embodiment is a production method that focuses on the fact that the ratio of fission products contained in metallic fuel 14 changes depending on the concentration of minor actinides contained in raw material 10 recovered from spent fuel. In contrast, the method for producing metallic fuel according to the present embodiment is a production method that focuses on the fact that the concentration of fission products contained in minor actinides recovered from spent fuel differs depending on the type of spent fuel.
[0077] The method for producing metallic fuel according to the present embodiment will be described with reference to the flow chart of Fig. 5. In the flow chart of Fig. 5, a production method using two types of raw materials 10.210 will be described, but it is also possible to use three or more types.
[0078] The manufacturing method of metallic fuel in this embodiment includes a composition evaluation step S201, a metal conversion step S202, a mixing ratio calculation step S203, a minor actinide mixing step S204a, a mixing step S204, and an injection casting step S105.
[0079] The composition evaluation step S201 is a step of evaluating the composition of the multiple raw materials 10, 210, and in the composition evaluation step S201, it is preferable to evaluate the composition of the raw materials 10, 210, such as the concentration of minor actinides and the concentration of fission products.
[0080] The raw material 10 is, for example, a minor actinide recovered from spent uranium fuel, and the raw material 210 is, for example, a minor actinide recovered from spent MOX fuel, containing a small amount of fission products as impurities, and preferably in the chemical form of oxide.
[0081] As in the first embodiment, the composition is preferably evaluated from the composition of the spent fuel and the processing conditions of the chemical processing of the spent fuel. The evaluation based on the composition of the spent fuel is preferably an evaluation by calculation based on the fuel composition before use, the burnup of the fuel, and the burnup history of the fuel. The evaluation based on the processing conditions of the chemical processing is preferably an evaluation based on the processing conditions of the wet reprocessing for recovering uranium and plutonium, or the processing conditions for separating minor actinides from the spent fuel from which uranium and plutonium have been recovered by wet reprocessing. The composition may also be evaluated by chemical analysis of a part of the raw materials 10, 210.
[0082] The metal conversion step S202 is a step in which each of the multiple raw materials 10, 210 whose components have been evaluated in the composition evaluation step S201 is converted into a metal by a method such as electrolytic reduction to obtain multiple metallic minor actinides 11, 211. Each of the raw materials 10, 210 is immersed in a high-temperature chloride molten salt and converted into a metal by electrolysis.
[0083] The mixing ratio calculation process S203 is a process of calculating, for example by a calculation device, the mixing ratio of each of multiple metallic minor actinides 11, 211 and the mixing ratio of metallic minor actinides 311, which is a mixture of multiple metallic minor actinides 11, 211, and other fuel materials 12, based on the composition of the raw materials 10, 210 evaluated in the composition evaluation process S201, so that the concentration of fission products in the metallic fuel 214 is below the reference value of 0.3 wt% and the minor actinide concentration in the metallic fuel 214 is the desired value of around 5%.
[0084] The mixing ratio calculation step S203 calculates a mixing ratio based on the composition data evaluated in the composition evaluation step S201, and outputs the mixing ratio to the minor actinide mixing step S204a and the mixing step S204. Therefore, the mixing ratio calculation step S203 is not a step of processing a substance like the other steps, but a step of processing data, and therefore in Fig. 5, the data input to and output from the mixing ratio calculation step S203 is indicated by a dotted line.
[0085] The minor actinide mixing step S204a is a step of mixing a plurality of metallic minor actinides 11, 211 according to the mixing ratio calculated in the mixing ratio calculation step S203 to produce one metallic minor actinide 311. Note that a plurality of raw materials 10, 210 may be mixed before the metal conversion step S202 and converted into one metallic minor actinide 311 in the metal conversion step S202. In this case, the minor actinide mixing step S204a is unnecessary.
[0086] The mixing step S204 is a step of mixing the metallic minor actinide 311 and the other fuel material 12 according to the mixing ratio calculated in the mixing ratio calculation step S203, and melting the mixture at a high temperature to produce an alloy 213.
[0087] The other fuel material 12 is preferably uranium, plutonium, and zirconium, as in the first embodiment. The chemical form of the other fuel material 12 is preferably a metal. The uranium and plutonium may be recovered by reprocessing spent nuclear fuel.
[0088] In the injection casting process S105, the alloy 213 mixed in the mixing process S204 is melted as in the first embodiment, injected into a glass sheath tube, cast into a rod shape, and then cooled to remove the metal fuel 214, which is a fuel slug, from the sheath tube.
[0089] Through these processes, metallic fuel can be produced from multiple raw materials10,210 with a desired minor actinide concentration of approximately 5% and a fission product concentration of less than the standard value of 0.3 wt%.
[0090] [effect] In the method for manufacturing metallic fuel in this embodiment, in a composition evaluation process S201 for evaluating the composition, the composition of multiple raw materials 10, 210 is evaluated, and in a mixing ratio calculation process S203 for calculating the mixing ratio, the mixing ratio of multiple metallic minor actinides 11, 211 obtained by metal conversion of the multiple raw materials 10, 210 and other fuel materials 12 is calculated, and in a process for obtaining an alloy, the multiple metallic minor actinides 11, 211 are mixed with the other fuel materials 12 based on the mixing ratio of the multiple metallic minor actinides 11, 211 and the other fuel materials 12.
[0091] That is, the method for producing metallic fuel according to this embodiment is a production method that uses a plurality of raw materials, for example minor actinides recovered from each of spent uranium fuel and spent MOX fuel, as raw materials.
[0092] The ratio of fission products contained in minor actinides recovered from spent uranium fuel is 0.071, as shown in the table in Figure 2. If metallic fuel is produced so that the concentration of metallic minor actinide-11, which is obtained by converting these minor actinides into metal in the metal conversion process S202, is around 5%, the concentration of fission products contained in the metallic fuel will be 0.36 wt%, as shown in the table in Figure 3. Therefore, it exceeds the standard value of 0.3 wt% or less.
[0093] Therefore, in this embodiment, based on the ratio of fission products contained in the minor actinides recovered from spent MOX fuel, which is the composition evaluated in the composition evaluation step S201, that is, 0.017 (see the table in Figure 2), the mixing ratio of metallic minor actinide 11 derived from spent uranium fuel and metallic minor actinide 211 derived from spent MOX fuel is calculated in the mixing ratio calculation step S203.
[0094] For example, if the mixing ratio of metallic minor actinide 11 derived from spent uranium fuel and metallic minor actinide 211 derived from spent MOX fuel is 1:1, the concentration of fission products contained in metallic fuel 214 will be 0.22 wt% (see table in Figure 3), which can be kept below the standard value of 0.3 wt%.
[0095] In other words, in this embodiment, by changing the mixing ratio of multiple metal minor actinides 11, 211 depending on the composition of multiple raw materials 10, 210, it is possible to produce metal fuel 214 in which the concentration of fission products is suppressed to the standard value of 0.3 wt% or less without additionally refining the raw materials.
[0096] The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.
[0097] In addition, the above configurations, functions, etc. may be realized in hardware, for example, by designing some or all of them as an integrated circuit. In addition, the above configurations, functions, etc. may be realized in software by a processor (microcomputer) interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD. [Explanation of symbols]
[0098] 10,210…Raw materials, 11,211…Minor actinide metals, 12…Fuel materials, 13,213…Alloys, 14,214…Metal fuel
Claims
1. A method for producing metallic fuel containing minor actinides, comprising the steps of: Evaluating the composition of at least one of the metallic fuel materials, the at least one material including a minor actinide; calculating a mixing ratio of at least one metallic minor actinide obtained by metal conversion of each of the at least one raw material and another fuel material, by referring to the composition, so that a concentration of fission products in the metallic fuel is equal to or less than a reference value and a concentration of minor actinides in the metallic fuel is a desired value; A method for manufacturing metallic fuel, comprising mixing the at least one metallic minor actinide and the other fuel material based on the mixing ratio and melting the mixture to obtain an alloy, which is then used as the metallic fuel.
2. 2. The method of claim 1, further comprising the steps of: In the step of evaluating the composition, a composition of one raw material is evaluated, In the step of calculating the mixing ratio, a mixing ratio between one metallic minor actinide obtained by metal conversion of the one raw material and another fuel material is calculated, A method for manufacturing metallic fuel, characterized in that in the step of obtaining the alloy, the one metallic minor actinide and the other fuel material are mixed based on a mixing ratio of the one metallic minor actinide and the other fuel material.
3. 2. The method of claim 1, further comprising the steps of: In the step of evaluating the composition, compositions of the plurality of raw materials are evaluated, In the step of calculating the mixing ratio, a mixing ratio between a plurality of metallic minor actinides obtained by metal conversion of each of the plurality of raw materials and other fuel materials is calculated, A method for manufacturing metallic fuel, characterized in that in the step of obtaining the alloy, the multiple metallic minor actinides are mixed with the other fuel material based on a mixing ratio of the multiple metallic minor actinides and the other fuel material.
4. 2. The method of claim 1, further comprising the steps of: A method for producing metallic fuel, wherein the raw material is a minor actinide recovered by reprocessing spent fuel.
5. The method for producing metallic fuel according to claim 4, A method for producing metallic fuel, characterized in that the composition is evaluated from the composition of the spent fuel and the processing conditions of chemical processing of the spent fuel.
6. 2. The method of claim 1, further comprising the steps of: The method for producing metallic fuel, wherein the composition includes a minor actinide concentration and a fission product concentration in the raw material.
7. 2. The method of claim 1, further comprising the steps of: A method for producing metallic fuel, wherein the other fuel materials are uranium, plutonium, and zirconium.
8. 2. The method of claim 1, further comprising the steps of: A method for producing metallic fuel, wherein the reference value is 0.3 wt %.
9. The method for producing metallic fuel according to claim 3, A method for producing metallic fuel, characterized in that the multiple metallic minor actinides in the step of obtaining the alloy are mixed in advance.
10. The method for producing metallic fuel according to claim 9, A method for producing metallic fuel, comprising the step of mixing the plurality of metallic minor actinides.
11. The method for producing metallic fuel according to claim 3, A method for producing metallic fuel, comprising mixing the plurality of raw materials before metal conversion.