Evaluation method, evaluation device, and program

Abstract

This invention provides a method for evaluating the properties of fuel debris containing a mixture of nuclear fuels with varying burnup levels. [Solution] The evaluation method includes the step of calculating the fissile material ratio indicating the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Cm-244 count rate and the amount of fissile material and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and the amount of fissile material and the fissile material ratio.

Description

Technical Field

[0001] The present disclosure relates to an evaluation method, an evaluation apparatus, and a program for evaluating the properties of fuel debris.

Background Art

[0002] In the reactor containment vessel of the Fukushima Daiichi Nuclear Power Plant, fuel debris remains, which is formed by melting nuclear fuel and mixing with various substances. In the future, the removal of fuel debris is planned. In order to properly store and process the removed fuel debris, it is necessary to understand the properties of the fuel debris. As part of understanding the properties of fuel debris, it is expected to evaluate the contents of nuclear fuel substances and radionuclides in the fuel debris by non-destructive measurement.

[0003] It is not possible to non-destructively measure all of the nuclear fuel substances and radionuclides in the fuel debris. As a method for evaluating nuclear fuel substances and radionuclides that are difficult to measure, it is common to measure measurable fissile nuclides and radionuclides and multiply the measurement results by a separately set nuclide composition ratio for evaluation.

[0004] It is known that the nuclide composition ratio of nuclear fuel changes depending on its burnup. For ordinary nuclear fuel, it is possible to identify the burnup from the operation history and theoretically set the nuclide composition ratio from the burnup. However, the fuel debris at the Fukushima Daiichi Nuclear Power Plant contains nuclear fuels with various burnups, and since the mixing ratio is unknown, it is impossible to theoretically set the nuclide composition ratio.

[0005] Patent Document 1 discloses a method for evaluating the burnup of nuclear fuel material using the ratio of the neutron count rate derived from Cm-244 to the gamma-ray count rate derived from Eu-154 (hereinafter referred to as the "Cm-224 / Eu-154 count rate ratio"). In contrast, the inventors have confirmed through trial calculations based on simulation results that no clear correlation can be obtained between the "Cm-244 / Eu-154 count rate ratio" and the "fissile material ratio" in fuel debris containing a mixture of nuclear fuels of various burnup levels. This is because the abundance of Cm-244 and Eu-154 increases as burnup progresses, and when nuclear fuels of various burnup levels are mixed, the "Cm-224 / Eu-154 count rate ratio" does not provide a correlation corresponding to the mixing state of the fuels. This indicates that it is impossible to set the burnup level and nuclide composition ratio from the "Cm-224 / Eu-154 count rate ratio". The "fissile material ratio" is a value related to burnup and nuclide composition ratio. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5951538 [Overview of the project] [Problems that the invention aims to solve]

[0007] There is a need for methods to evaluate the properties of fuel debris, which is a mixture of nuclear fuels with varying burnup levels.

[0008] This disclosure provides an evaluation method, an evaluation apparatus, and a program that can solve the above-mentioned problems. [Means for solving the problem]

[0009] The evaluation method of the present disclosure is a computer-based evaluation method comprising the step of calculating a fissile material ratio indicating the properties of the fuel debris based on evaluation values ​​of the Cm-244 count rate and fissile material amount of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and fissile material amount and the fissile material ratio, and / or evaluation values ​​of the Eu-154 count rate and fissile material amount of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and fissile material amount and the fissile material ratio.

[0010] The evaluation apparatus of the present disclosure includes means for calculating a fissile material ratio indicating the properties of the fuel debris based on evaluation values ​​of the Cm-244 count rate and fissile material amount of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and fissile material amount and the fissile material ratio, and / or evaluation values ​​of the Eu-154 count rate and fissile material amount of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and fissile material amount and the fissile material ratio.

[0011] The program of this disclosure causes a computer to perform the step of calculating a fissile material ratio that indicates the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and the amount of fissile material of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and the amount of fissile material and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and the amount of fissile material and the fissile material ratio. [Effects of the Invention]

[0012] The evaluation apparatus, evaluation method, and program of this disclosure can be used to evaluate the properties of fuel debris containing a mixture of nuclear fuels of various burnup levels. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing an example of an evaluation apparatus according to an embodiment. [Figure 2]This figure shows an example of the correlation between the Cm-244 count rate and the ratio of fissile material content and the fissile material content ratio in a state in which nuclear fuels of various burnups according to the embodiment are mixed in various mixing ratios. [Figure 3] This figure shows an example of the correlation between the Eu-154 count rate and the ratio of fissile material content and the fissile material content ratio in a state in which nuclear fuels of various burnups according to the embodiment are mixed in various mixing ratios. [Figure 4] This figure shows an example of a process for determining fuel debris burnup and nuclide composition from the fissile material ratio according to the embodiment. [Figure 5] This flowchart shows an example of a fuel debris properties evaluation process according to the embodiment. [Figure 6] This figure shows an example of the hardware configuration of the evaluation device of the embodiment. [Modes for carrying out the invention]

[0014] (composition) The method for evaluating the properties of fuel debris according to this disclosure will be described below with reference to the drawings. Figure 1 is a block diagram showing an example of an evaluation apparatus according to the embodiment. The evaluation device 10 comprises an input receiving unit 11, an estimation unit 12, and a storage unit 13.

[0015] The input receiving unit 11 receives information and instructions entered using input devices such as keyboards, mice, touch panels, and buttons. For example, the input receiving unit 11 receives information necessary for evaluating the composition of fuel debris (e.g., the Cm-244 count rate and / or Eu-154 count rate of the fuel debris, and an estimated value of the amount of fissile material). The input receiving unit 11 records the received information in the storage unit 13 or outputs it to the estimation unit 12.

[0016] The estimation unit 12 estimates various types of information indicating the properties of the fuel debris to be evaluated (for example, combustion degree, content of nuclear fuel materials, nuclide composition such as content of radionuclides, etc.) using functions, data tables, learned models, etc. stored in the storage unit 13. The estimation unit 12 outputs the estimation result to a display device, an electronic file, etc.

[0017] The storage unit 13 stores various types of setting information, processing data during calculations, etc. The storage unit 13 stores functions, data tables, learned models, etc. used for evaluating the properties of fuel debris. Functions used for estimation include functions showing the correlation between the Cm-244 count rate and the ratio of fissile material amount and the ratio of fissile material amount, as exemplified in FIG. 2, functions showing the correlation between the Eu-154 count rate and the ratio of fissile material amount and the ratio of fissile material amount, as exemplified in FIG. 3, functions showing the relationship between the ratio of fissile material amount and combustion degree and nuclide composition, as exemplified in FIG. 4, etc.

[0018] FIG. 2 shows an example of the correlation between the Cm-244 count rate and the ratio of fissile material amount and the ratio of fissile material amount in a state where nuclear fuels with various combustion degrees are mixed at various mixing ratios. The vertical axis of Figure 2 shows the ratio of fissile material (wt%) in the fuel debris, and the horizontal axis shows the Cm-244 count rate ÷ fissile material amount × 100. The fissile material ratio is calculated as fissile material amount (kg) / nuclear fuel material amount (kg) × 100. The fissile material amount is the total weight of U-235 + Pu-239 + Pu-241 after burnup. The nuclear fuel material amount is the total weight of U + total weight of Pu after burnup. Each point in Figure 2 plots the "ratio of Cm-244 count rate to fissile material amount" and the "fissile material ratio," which are calculated from the Cm-244 count rate, fissile material amount, and nuclear fuel material amount obtained from measurements and analyses of fuel debris with mixed burnup levels. As shown in the figure, there is a correlation between the two, shown by curve K1. In other words, if the Cm-244 count rate and the amount of fissile material of fuel debris can be obtained, it is possible to calculate the "fissile material ratio," which indicates the properties of the fuel debris when nuclear fuels of various burnups are mixed together. The Cm-244 count rate can be measured using the passive neutron method, which measures neutrons emitted from the fuel debris, or by other methods. The amount of fissile material can be measured using the active neutron method, which measures neutrons emitted from the fuel debris when it is irradiated with neutrons, or by other methods. Alternatively, physical quantities related to Cm-244, such as an estimated value of the amount of Cm-244, may be used instead of the Cm-244 count rate, or physical quantities related to fissile material, such as the neutron count rate derived from fissile material, may be used instead of the amount of fissile material.

[0019] Figure 3 shows an example of the correlation between the Eu-154 count rate and the ratio of fissile material content in a mixture of nuclear fuels of various burnup levels in various proportions, and the ratio of fissile material content. The vertical axis of FIG. 3 indicates the mass ratio (wt%) of fissile materials in the fuel debris, and the horizontal axis indicates Eu-154 count rate ÷ fissile material mass × 100. Each point in FIG. 3 plots the "ratio of Eu-154 count rate and fissile material mass" and the "fissile material mass ratio" calculated from the Eu-154 count rate, fissile material mass, and nuclear fuel material mass obtained by measurement and analysis of fuel debris with mixed burn-up degrees. As shown in the figure, there is a correlation shown by curve K2 between the two. That is, if the Eu-154 count rate and fissile material mass of the fuel debris can be obtained, the "fissile material mass ratio" indicating the properties of the fuel debris in a state where nuclear fuels with various burn-up degrees are mixed can be calculated. The measured value of the Eu-154 count rate can be measured by the passive gamma method or other methods that measure gamma rays emitted from the fuel debris. Also, a physical quantity related to Eu-154 such as an evaluation value of Eu-154 may be used instead of the Eu-154 count rate.

[0020] As described above, the inventors confirmed that in fuel debris containing nuclear fuels of various burnup levels, a clear correlation could not be obtained between the "Cm-244 / Eu-154 counting rate ratio" and the "fissile material ratio." This is because, as burnup progresses, the abundance of Cm-244 and Eu-154 increases, and calculating the "Cm-244 / Eu-154 counting rate ratio" when nuclear fuels of various burnup levels are mixed together does not yield a correlation corresponding to the fuel level. In contrast, the inventors confirmed that a correlation exists between the "Cm-244 counting rate / fissile material ratio" and the "fissile material ratio," as shown in Figure 2, thus enabling an effective evaluation of burnup and nuclide composition. Furthermore, as shown in Figure 3, a correlation exists between the "Eu-154 counting rate / fissile material ratio" and the "fissile material ratio," thus enabling an effective evaluation of burnup and nuclide composition. These results are due to the effect that, as burnup progresses, the abundance of Cm-244 and Eu-154 increases, while the amount of fissile material decreases. Therefore, even when nuclear fuels of various burnup levels are mixed, taking the "ratio of Eu-154 count rate to fissile material" or the "ratio of Cm-244 count rate to fissile material" yields a correlation corresponding to the mixing state of the fuels. Here, the effective burnup / nuclide composition refers to the fact that while it is not possible to know what proportions of fuels of what burnup levels are mixed in the fuel debris, as a result of the mixing of fuels of various burnup levels, the overall burnup / nuclide composition of the fuel debris can be considered to be what it is. Note that in Figures 2 and 3, we used the ratio of "Eu-154 count rate / amount of fissile material" and the ratio of "Cm-244 count rate / amount of fissile material," but you can also swap the numerator and denominator and use the ratio of "amount of fissile material / Eu-154 count rate" and the ratio of "amount of fissile material / Cm-244 count rate."

[0021] As shown in Figures 2 and 3, the fissile material ratio of fuel debris can be calculated from the correlations. The fissile material ratio is related to the burnup and nuclide composition. For example, the fissile material ratio is considered to roughly represent the burnup. Furthermore, if the burnup is known, it is considered that the nuclide composition can be theoretically estimated from that burnup. Figure 4 shows an example of a method for estimating the effective burnup and nuclide composition (content of nuclear fuel material and radionuclides) from the fissile material ratio. For example, as shown in Figure 4(a), an estimator 41 is created that outputs the content of nuclear fuel material when the fissile material ratio is input, by analyzing and learning the relationship between the fissile material ratio and the content of nuclear fuel material in the fuel debris. Then, the fissile material ratio estimated based on the correlations in Figures 2 and 3 is input to the estimator 41 to estimate the content of nuclear fuel material. Similarly, as shown in Figure 4(b), an estimator 42 is created that outputs the radionuclide content when the fissile material ratio is input, by analyzing and learning the relationship between the fissile material ratio and the radionuclide content of the fuel debris. Then, the fissile material ratio estimated based on the correlation in Figures 2 and 3 is input to the estimator 42 to estimate the radionuclide content. This makes it possible to evaluate the nuclide composition of the fuel debris. In addition, an estimator 43 is created that outputs the burnup when the fissile material ratio is input, by analyzing and learning the relationship between the fissile material ratio and the burnup of the fuel debris. Then, the fissile material ratio estimated based on the correlation in Figures 2 and 3 is input to the estimator 43 to estimate the effective burnup of the burning debris.

[0022] (operation) Figure 5 is a flowchart showing an example of a fuel debris properties evaluation process according to the embodiment. First, the user inputs the Cm-224 count rate (measured by passive neutron method, etc.) and / or Eu-154 count rate (measured by passive gamma method, etc.) of the fuel debris to be evaluated, along with an evaluation value of the amount of fissile material measured by active neutron method, etc., into the evaluation device 10. The input reception unit 11 acquires this data (step S1) and records it in the storage unit 13.

[0023] Next, the estimation unit 12 obtains the fissile material ratio (step S2). For example, the estimation unit 12 calculates an estimated value of Cm-224 count rate ÷ fissile material amount and calculates the fissile material ratio corresponding to Cm-224 count rate ÷ fissile material amount by comparing it with the "function showing the correlation between the ratio of Cm-244 count rate and fissile material amount and the fissile material ratio (Figure 2)" stored in the memory unit 13. Alternatively, for example, the estimation unit 12 calculates an estimated value of Eu-154 count rate ÷ fissile material amount and calculates the fissile material ratio corresponding to Eu-154 count rate ÷ fissile material amount by comparing it with the "function showing the correlation between the ratio of Eu-154 count rate and fissile material amount and the fissile material ratio (Figure 3)" stored in the memory unit 13. Alternatively, instead of Figure 2, a function showing the correlation between the ratio of fissile material amount / Cm-224 count rate and the fissile material amount ratio may be prepared, and instead of Figure 3, a function showing the correlation between the ratio of fissile material amount / Eu-154 count rate and the fissile material amount ratio may be prepared to calculate the fissile material amount ratio.

[0024] Next, the estimation unit 12 estimates the burnup and / or nuclide composition of the fuel debris (step S3). For example, the estimation unit 12 inputs the fissile material ratio obtained in step S2 into the estimator 41 and obtains the estimated value of the nuclear fuel material content output by the estimator 41. For example, the estimation unit 12 inputs the fissile material ratio obtained in step S2 into the estimator 42 and obtains the estimated value of the radioactive nuclide content output by the estimator 42. For example, the estimation unit 12 inputs the fissile material ratio obtained in step S2 into the estimator 43 and obtains the estimated value of the burnup output by the estimator 43. The estimation unit 12 outputs the calculated estimated values ​​of burnup and nuclide composition (nuclear fuel material content and / or radioactive nuclide content) to a display device or the like. Alternatively, the estimation unit 12 may evaluate the burnup and nuclide composition ratio by combining the ratio of Cm-224 count rate / fissile material amount and the ratio of Eu-154 count rate / fissile material amount. For example, the estimation unit 12 may calculate a weighted average of the burnup estimated using the ratio of Cm-224 count rate to fissile material and the burnup estimated using the ratio of Eu-154 count rate to fissile material, and use this value as the estimated burnup of the fuel debris. Similarly, the estimation unit 12 may calculate a weighted average of the nuclear fuel material content estimated using the ratio of Cm-224 count rate to fissile material and the nuclear fuel material content estimated using the ratio of Eu-154 count rate to fissile material, and use this value as the estimated nuclear fuel material content contained in the fuel debris. The same applies to the radionuclide content. This makes it possible to evaluate the burnup and nuclide composition of the fuel debris.

[0025] (effect) According to this embodiment, the "ratio of Cm-224 count rate to fissile material amount" and / or the "ratio of Eu-154 count rate to fissile material amount" are calculated, and the "fissile material amount ratio" indicating the properties of the fuel debris is calculated from the "ratio of Cm-224 count rate to fissile material amount" and / or the "ratio of Eu-154 count rate to fissile material amount". Furthermore, the effective burnup and nuclide composition of the fuel debris are estimated from the "fissile material amount ratio". This makes it possible to evaluate the effective burnup and nuclide composition ratio of fuel debris containing a mixture of nuclear fuels with various burnup levels, and improves the accuracy of evaluation of the amount of nuclear fuel material and radioactive nuclides when combining non-destructive measurement methods and nuclide composition ratio methods. In addition, by accurately evaluating the properties of the fuel debris, stable storage and processing of the fuel debris becomes possible.

[0026] Figure 6 shows an example of the hardware configuration of the evaluation device. The computer 900 includes a CPU 901, main memory 902, auxiliary memory 903, input / output interface 904, and communication interface 905. The evaluation device 10 described above is implemented in the computer 900. The functions described above are stored in the auxiliary memory 903 in the form of programs. The CPU 901 reads the program from the auxiliary memory 903, expands it into the main memory 902, and executes the above processing according to the program. The CPU 901 also allocates a memory area in the main memory 902 according to the program. The CPU 901 also allocates a memory area in the auxiliary memory 903 to store the data being processed according to the program.

[0027] Furthermore, a program to implement all or part of the functions of the evaluation device 10 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed to perform processing by each functional unit. Here, "computer system" includes hardware such as the OS and peripheral devices. Also, if a WWW system is used, "computer system" also includes the homepage provisioning environment (or display environment). Furthermore, "computer-readable recording medium" refers to portable media such as CDs, DVDs, USBs, and storage devices such as hard disks built into the computer system. In addition, if this program is distributed to computer 900 via a communication line, computer 900 that receives the program may load it into main memory 902 and execute the above processing. Furthermore, the above program may be for implementing part of the functions described above, and may also be for implementing the above functions in combination with programs already recorded in the computer system.

[0028] As described above, several embodiments relating to this disclosure have been explained, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0029] <Note> The evaluation method, evaluation apparatus, and program described in the embodiment can be understood, for example, as follows.

[0030] (1) The evaluation method according to the first embodiment is an evaluation method performed by a computer, and includes the step of calculating the fissile material ratio indicating the properties of the fuel debris based on the evaluation values ​​of the Cm-244 count rate and the amount of fissile material of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and the amount of fissile material and the fissile material ratio, and / or the evaluation values ​​of the Eu-154 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and the amount of fissile material and the fissile material ratio. This allows for the evaluation of the properties of fuel debris.

[0031] (2) The evaluation method relating to the second aspect is the evaluation method of (1), wherein the ratio of the Cm-244 count rate to the amount of fissile material is calculated by Cm-244 count rate ÷ amount of fissile material or by amount of fissile material ÷ Cm-244 count rate, and the ratio of the Eu-154 count rate to the amount of fissile material is calculated by Eu-154 count rate ÷ amount of fissile material or by amount of fissile material ÷ Eu-154 count rate. This allows for the evaluation of the properties of fuel debris.

[0032] (3) The evaluation method relating to the third aspect is the evaluation method of (1) or (2), further comprising the step of estimating the burnup and / or nuclide composition of the fuel debris from the calculated fissile material ratio. This allows for the evaluation of the burnup and radionuclide composition of fuel debris.

[0033] (4) The evaluation method relating to the fourth aspect is the evaluation method of (3), wherein the nuclide composition is the content of nuclear fuel material and / or radioactive nuclide. This makes it possible to evaluate the content of nuclear fuel material and / or radionuclides in the fuel debris.

[0034] (5) The evaluation method relating to the fifth aspect is the evaluation method of (3) or (4), wherein in the estimation step, the burnup of the fuel debris is estimated by inputting the amount of fissile material calculated in the calculation step into a function that outputs the burnup of the fuel debris when the amount of fissile material is input, and the nuclide composition of the fuel debris is estimated by inputting the amount of fissile material calculated in the calculation step into a function that outputs the nuclide composition of the fuel debris when the amount of fissile material is input. This makes it possible to obtain the burnup and radionuclide composition of fuel debris.

[0035] (6) The evaluation device according to the sixth embodiment has means for calculating the fissile material ratio indicating the properties of the fuel debris based on the evaluation values ​​of the Cm-244 count rate and the amount of fissile material of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and the amount of fissile material and the fissile material ratio, and / or the evaluation values ​​of the Eu-154 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and the amount of fissile material and the fissile material ratio. This allows for the evaluation of the properties of fuel debris.

[0036] (7) The program according to the seventh embodiment causes a computer to perform the step of calculating a fissile material ratio that indicates the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and the amount of fissile material of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and the amount of fissile material and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and the amount of fissile material of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and the amount of fissile material and the fissile material ratio. This allows for the evaluation of the properties of fuel debris. [Explanation of Symbols]

[0037] 10. Evaluation device 11. Input Reception Section 12...Estimation part 13...Storage section 41, 42, 43... Estimator 900... Computer 901···CPU 902...Main memory 903...Auxiliary storage device 904... Input / Output Interface 905...Communication Interface

Claims

1. A computer-based evaluation method, A step of calculating the fissile material ratio that indicates the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and fissile material amount of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and fissile material amount and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and fissile material amount of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and fissile material amount and the fissile material ratio, A method of evaluation that includes [something].

2. The ratio of the Cm-244 count rate to the amount of fissile material is calculated by either the Cm-244 count rate ÷ the amount of fissile material, or the amount of fissile material ÷ the Cm-244 count rate. The ratio of the Eu-154 count rate to the amount of fissile material is calculated by either the Eu-154 count rate ÷ the amount of fissile material, or the amount of fissile material ÷ the Eu-154 count rate. The evaluation method according to claim 1.

3. A step of estimating the burnup and / or nuclide composition of the fuel debris from the calculated ratio of fissile material, The evaluation method according to claim 1 or claim 2, further comprising:

4. The aforementioned nuclide composition is the content of nuclear fuel material and / or radioactive nuclide. The evaluation method described in claim 3.

5. In the estimation step described above, The burnup of the fuel debris is estimated by inputting the fissile material ratio, which was calculated in the above calculation step, into a function that outputs the burnup of the fuel debris when the fissile material ratio is input. The function that outputs the nuclide composition of fuel debris when the fissile material ratio is input is used to estimate the nuclide composition of the fuel debris by inputting the fissile material ratio calculated in the calculation step described above. The evaluation method described in claim 3.

6. A means for calculating the fissile material ratio indicating the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and fissile material amount of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and fissile material amount and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and fissile material amount of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and fissile material amount and the fissile material ratio, An evaluation device having the following features.

7. On the computer, A step of calculating the fissile material ratio that indicates the properties of the fuel debris based on the evaluated values ​​of the Cm-244 count rate and fissile material amount of the fuel debris to be evaluated, data showing the correlation between the ratio of the Cm-244 count rate and fissile material amount and the fissile material ratio, and / or the evaluated values ​​of the Eu-154 count rate and fissile material amount of the fuel debris, data showing the correlation between the ratio of the Eu-154 count rate and fissile material amount and the fissile material ratio, A program that executes the command.

Images