Critical margin estimation device and critical margin estimation method

Abstract

To provide a critical margin estimation device capable of estimating the critical margin of nuclear fuel materials stored in a storage container regardless of the material in the storage container.SOLUTION: A critical margin estimation device according to the present invention includes: a container state acquisition unit 201 that acquires the state of an in-container material 102 stored in a storage container 101; a physical information estimation unit 202 that estimates physical information on the in-container material 102 from the state of the in-container material 102; a critical margin evaluation unit 203 that calculates the effective multiplication factor of the storage container 101 from the physical information on the in-container material 102 and estimates the critical margin until the in-container material 102 reaches criticality; and a database 210 that stores surface condition, composition, density, and shape of materials that may become the in-container material 102. The state of the in-container material 102 includes surface condition, composition, density, shape, and height of the in-container material 102. The physical information on the in-container material 102 includes the average height in the container and the atomic number ratio of uranium to hydrogen.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for estimating a critical margin, which is a margin until reaching criticality, for nuclear fuel material stored in a storage container.

Background Art

[0002] Radioactive waste containing nuclear fuel material needs to be stored stably while being stored in a storage container to ensure critical safety regarding nuclear fission. An example of the prior art for appropriately holding a storage container containing radioactive waste containing nuclear fuel material is described in Patent Document 1. The apparatus for storing nuclear fuel material described in Patent Document 1 includes an outer container having an upper opening and a region capable of accommodating a storage container therein, a neutron detector for measuring the neutron count rate in the storage container, and an arithmetic unit for obtaining the amount of nuclear fuel material that may cause criticality in the storage container based on the measurement result of the neutron detector. Even when the environment around the storage container changes, it is possible to ensure subcriticality of the stored nuclear fuel material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, the amount of nuclear fuel material that may cause criticality in the storage container is obtained based on the neutron count rate in the storage container measured by the neutron detector. Inside the storage container, there may be a plurality of types of nuclear fuel materials with different burnup degrees, or non-nuclear fuel materials such as neutron absorbers and moisture may be mixed. In the conventional technique, in such cases, it is not easy to obtain the amount of nuclear fuel material that may cause criticality in the storage container, and it is difficult to obtain the critical margin (margin until reaching criticality) of the nuclear fuel material stored in the storage container.

[0005] An object of the present invention is to provide a criticality margin estimation device and a criticality margin estimation method capable of estimating the criticality margin of nuclear fuel substances stored in a storage container regardless of the substances in the storage container.

Means for Solving the Problems

[0006] The criticality margin estimation device according to the present invention includes a container state acquisition unit that acquires a state regarding a substance in a container, which is radioactive waste stored in the storage container; a physical information estimation unit that estimates physical information of the substance in the container from the state regarding the substance in the container acquired by the container state acquisition unit; a criticality margin evaluation unit that obtains an effective multiplication factor of the storage container from the physical information of the substance in the container estimated by the physical information estimation unit and estimates a criticality margin, which is a margin until the substance in the container reaches criticality, from the effective multiplication factor; and a database that stores surface state, composition, density, and shape for substances that can be the substance in the container. The state regarding the substance in the container includes the surface state, the composition, the density, the shape, and the height of the substance in the container. The physical information of the substance in the container is an average height in the container of the substance in the container in a state accommodated in the storage container and an atomic number ratio of uranium to hydrogen.

[0007] The criticality margin estimation method according to the present invention includes a container state acquisition step of acquiring a state of the container material, which is radioactive waste stored in a storage container, a physical information estimation step of estimating physical information of the container material from the state of the container material acquired in the container state acquisition step, and a criticality margin evaluation step of calculating an effective multiplication factor of the storage container from the physical information of the container material estimated in the physical information estimation step, and estimating a criticality margin, which is a margin until the container material reaches criticality, from the effective multiplication factor. The state of the container material includes the surface state, composition, density, shape, and height of the container material. The physical information of the container material is an average container height, which is an average height of the container material when it is contained in the storage container, and an atomic ratio of uranium to hydrogen. In the container state acquisition step, the surface state of the substance in the container and the distance of the substance in the container from the top of the storage container are measured by a surface measurement device, the height is calculated from the distance, and the composition, density, and shape are acquired by referring to a database that stores the surface state, composition, density, and shape of substances that may become the substance in the container using the surface state acquired by the surface measurement device. In the physical information estimation step, the average height in the container and the atomic ratio are estimated using the composition, density, shape, and height of the substance in the container acquired in the container state acquisition step. Effect of the Invention

[0008] According to the present invention, it is possible to provide a criticality margin estimation device and a criticality margin estimation method capable of estimating the criticality margin of nuclear fuel material contained in a storage container, regardless of the material inside the storage container. [Brief description of the drawings]

[0009]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0010] In this specification, the margin until the nuclear fuel substance reaches criticality is called the critical margin. The critical margin is represented by the difference between the effective multiplication factor keff of the storage container storing radioactive waste containing the nuclear fuel substance and the value of the effective multiplication factor at which criticality occurs (=1).

[0011] Hereinafter, a criticality margin estimation device and a criticality margin estimation method according to an embodiment of the present invention will be described with reference to the drawings. In the drawings used in this specification, the same or corresponding components are designated by the same reference numerals, and repeated description of these components may be omitted. EXAMPLES

[0012] A criticality margin estimation device and a criticality margin estimation method according to a first embodiment of the present invention will be described. In this embodiment, an example of a device and a method for estimating the criticality margin of nuclear fuel material stored in a storage container will be described. It is assumed that the nuclear fuel material is contained in radioactive waste stored in a storage container.

[0013] In the following explanation, the radioactive waste stored in the storage container is also referred to as the "container material." The container material is usually a mixture of multiple types of materials (e.g., uranium dioxide and iron).

[0014] 1A to 1C are diagrams showing an example of a substance 102 contained in a container 101. FIG.

[0015] 1A shows a sand-like (or powder-like) substance 102a in a container. The sand-like substance 102a in the container is a substance whose individual contours cannot be recognized by the naked eye.

[0016] 1B shows a lump of the substance 102b in the container. The lump of the substance 102b in the container is a substance in the container whose individual contours can be visually recognized.

[0017] 1C shows the in-container material 102c registered in the database 210 shown in FIG. The in-container material 102c registered in the database 210 is, for example, radioactive waste consisting of structures (e.g., pipes, pillars, etc.) in a nuclear facility. The shape, size, material, etc. of such radioactive waste are known, and can be registered in advance in the database 210. Note that the in-container material 102c registered in the database 210 is in-container material (lump-shaped in-container material) whose individual contours can be recognized by visual inspection.

[0018] The storage container 101 is a container for storing any radioactive waste, and can store, for example, the container substance 102 (102a to 102c) shown in Fig. 1A to Fig. 1C. The shape of the storage container 101 is arbitrary, for example, cylindrical or rectangular tubular. In this embodiment, the storage container 101 will be mainly described as being cylindrical.

[0019] The storage container 101 may store not only radioactive waste containing nuclear fuel material, but also radioactive waste not containing nuclear fuel material as the material 102 inside the container. In this embodiment, the material 102 inside the container is radioactive waste containing uranium, which is a nuclear fuel material.

[0020] FIG. 2 is a diagram showing the configuration of the criticality margin estimation device according to this embodiment.

[0021] The criticality margin estimation device according to this embodiment includes a vessel state acquisition unit 201 , a physical information estimation unit 202 , a criticality margin evaluation unit 203 , a criticality margin display unit 204 , a database 210 , and an input unit 211 .

[0022] The container state acquisition unit 201 acquires a state related to the substance 102 in the container. The state related to the substance 102 in the container refers to information on the characteristics of the substance 102 in the container, and includes, for example, the surface state, composition c, density ρ, shape s, height h, volume, and mass M of the substance 102 in the container.

[0023] The surface condition refers to the shape of the surface of the substance (e.g., the size of the unevenness) and color. The composition c refers to the mixing ratio of substances contained in the substance 102 in the container, which is a mixture, and is expressed as, for example, 80% uranium dioxide and 20% iron. The shape s indicates whether the substance 102 in the container is sand-like (substance 102a in the container in FIG. 1A) or clump-like (substance 102b in the container in FIG. 1B). The height h refers to the height of the substance 102 in the container when it is contained in the storage container 101 (the distance from the bottom of the storage container 101 to the top of the substance 102 in the container).

[0024] The physical information estimation unit 202 estimates the physical information of the substance 102 in the container from the state of the substance 102 in the container acquired by the container state acquisition unit 201. The physical information of the substance 102 in the container is, for example, a value necessary for calculating the effective multiplication factor keff of the storage container 101, and is the average height z inside the container and the atomic number ratio H / U of uranium and hydrogen. The average height z inside the container is the average height of the substance 102 in the container in the state of being stored in the storage container 101 (the average height of the substance 102 in the container from the bottom surface of the storage container 101).

[0025] The criticality margin evaluation unit 203 obtains the effective multiplication factor keff of the storage container 101 from the physical information of the substance 102 in the container estimated by the physical information estimation unit 202 and estimates the criticality margin. The criticality margin is the margin until the nuclear fuel material reaches criticality, and in this embodiment, it is the margin until the substance 102 in the container reaches criticality.

[0026] The criticality margin display unit 204 displays the effective multiplication factor keff and the criticality margin obtained by the criticality margin evaluation unit 203. The criticality margin display unit 204 further displays the average height z inside the container estimated by the physical information estimation unit 202, the atomic number ratio H / U of uranium and hydrogen, the surface state, composition c, density ρ, shape s, height h, volume, and mass M of the substance 102 in the container acquired by the container state acquisition unit 201.

[0027] The database 210 stores the information required by the container state acquisition unit 201, the physical information estimation unit 202, and the criticality margin evaluation unit 203. For example, the database 210 stores in advance information such as the surface state, composition c, density ρ, and shape s of substances that may be stored in the storage container 101 (substances that can become the substance 102 in the container) as substance information. The composition c can be obtained, for example, by analysis with a mass spectrometer or the like. The density ρ can be obtained, for example, by measurement with an X-ray source and an X-ray detector or the like. Note that it is assumed that all the shapes s registered in the database 210 are in a lump shape.

[0028] The database 210 also stores substance information about radioactive waste (substance inside the container 102) that was previously stored in the storage container 101.

[0029] The input unit 211 is a device for registering information in the database 210. The input unit 211 is operated by the user, and for example, registers substance information about substances that can become the substance inside the container 102 in the database 210 in advance.

[0030] The user can operate the input unit 211 to associate the surface state, composition c, density ρ, and shape s for substances that can become the substance inside the container 102, and register them in the database 210 as substance information. For example, for structures (such as pipes and columns) inside a nuclear facility, since the surface state, composition c, density ρ, and shape s are known, the composition c, density ρ, and shape s can be associated with the surface state and registered in the database 210.

[0031] Therefore, by using the substance information registered in the database 210, if the surface state of a substance is specified, the composition c, density ρ, and shape s corresponding to this surface state can be obtained. For example, if a structure inside a nuclear facility is the substance inside the container 102, the composition c, density ρ, and shape s of the substance inside the container 102 can be estimated from the surface state of the substance inside the container 102 using the substance information registered in the database 210.

[0032] The container state acquisition unit 201 can acquire the substance information registered by the user in the database 210 from the database 210. For example, when the surface state of the substance inside the container 102 acquired as the state regarding the substance inside the container 102 is included in the substance information registered in the database 210, the composition c, density ρ, and shape s registered in the database 210 corresponding to the acquired surface state can be regarded as the composition c, density ρ, and shape s of this substance inside the container 102.

[0033] FIG. 3 is a flowchart showing the procedure of the criticality margin estimation method according to this embodiment.

[0034] Step 301 is a step in which the container state acquisition unit 201 acquires the state regarding the substance 102 inside the container.

[0035] Step 302 is a step in which the physical information estimation unit 202 estimates the physical information of the substance 102 inside the container from the state regarding the substance 102 inside the container.

[0036] Step 303 is a step in which the critical margin evaluation unit 203 obtains the effective multiplication factor keff of the storage container 101 from the physical information of the substance 102 inside the container and estimates the critical margin.

[0037] The container state acquisition unit 201 will be described with reference to FIGS. 4 to 6.

[0038] When the radioactive waste 403 containing nuclear fuel material is stored in the storage container 101 and after it is stored, the container state acquisition unit 201 can measure this radioactive waste 403 (that is, the substance 102 inside the container) with the surface measurement device 401 to acquire the state regarding the substance 102 inside the container.

[0039] FIG. 4 is a diagram showing an example in which the container state acquisition unit 201 acquires the state regarding the substance 102 inside the container by measuring the radioactive waste 403 stored in the storage container 101.

[0040] The container state acquisition unit 201 includes a surface measurement device 401. The surface measurement device 401 can be composed of, for example, an optical camera, a point cloud sensor, etc. The surface measurement device 401 can image or measure the radioactive waste 403 stored in the storage container 101 to measure the state regarding this radioactive waste 403, for example, the surface state and the volume.

[0041] The radioactive waste 403 is held by, for example, a remote operation manipulator 402 and stored in the storage container 101. Note that the radioactive waste 403 may be stored in the storage container 101 by being sucked by a device other than the remote operation manipulator 402, for example, a suction device.

[0042] The surface measurement device 401 is installed at a position where the remote manipulator 402 grips the radioactive waste 403 or at a position where the remote manipulator 402 stores the radioactive waste 403 in the storage container 101. The surface measurement device 401 measures the surface state and volume of the radioactive waste 403 when the radioactive waste 403 is gripped by the remote manipulator 402 or stored in the storage container 101.

[0043] The container state acquisition unit 201 acquires the surface state and volume of the radioactive waste 403 measured by the surface measurement device 401 as the state regarding the substance 102 inside the container.

[0044] FIG. 5 is a diagram showing an example in which the container state acquisition unit 201 acquires the state regarding the substance 102 inside the container by measuring the substance 102 inside the container, which is the radioactive waste 403 stored in the storage container 101.

[0045] The surface measurement device 401 is installed above the storage container 101 and measures the surface state and volume of the substance 102 inside the container stored in the storage container 101. Further, the surface measurement device 401 measures the distance d from the topmost part of the storage container 101 for the substance 102 inside the container.

[0046] The container state acquisition unit 201 can acquire the state regarding the substance 102 inside the container, such as the surface state and volume, using the surface measurement device 401. Further, the container state acquisition unit 201 can acquire the distance d from the topmost part of the storage container 101 for the substance 102 inside the container using the surface measurement device 401.

[0047] Also, the container state acquisition unit 201 can include a mass meter 504 installed in the storage container 101. The mass meter 504 measures the mass M of the substance 102 inside the container. The container state acquisition unit 201 can acquire the mass M of the substance 102 inside the container using the mass meter 504.

[0048] In addition, the container state acquisition unit 201 can include an X-ray source 502 and an X-ray detector 503 installed with the storage containers 101 sandwiched therebetween. The X-ray source 502 and the X-ray detector 503 measure the density ρ of the substance 102 inside the container from one direction or multiple directions. The container state acquisition unit 201 can acquire the distribution (density distribution) of the density ρ of the substance 102 inside the container by using the X-ray source 502 and the X-ray detector 503.

[0049] In the following description, the two-dimensional position on the plane parallel to the bottom surface of the storage container 101 is represented by coordinates (x, y). The container state acquisition unit 201 can obtain the distribution of the state regarding the substance 102 inside the container for the two-dimensional position (x, y) of the storage container 101.

[0050] FIG. 6 is a diagram showing the distribution of the height h of the substance 102 inside the container acquired by the container state acquisition unit 201.

[0051] The distribution h(x, y) of the height h of the substance 102 inside the container is obtained by using the distribution d(x, y) of the distance d acquired by the container state acquisition unit 201 and the height H (distance from the topmost part to the bottom surface) of the storage container 101. h(x, y)=H - d(x, y) (1) and is expressed as such.

[0052] When the distribution h(x, y) of the height h of the substance 102 inside the container can be regarded as constant for the two-dimensional position (x, y), the distribution h(x, y) is obtained by using the total volume V of the substance 102 inside the container (total volume of all the substances 102 inside the storage container 101) acquired by the container state acquisition unit 201 and the inner diameter R of the storage container 101. h(x, y)=V / {π(R / 2) 2} (2) and can be expressed as such.

[0053] The container state acquisition unit 201 acquires the distribution h(x, y) of the height h of the substance 102 inside the container according to formula (1) or formula (2).

[0054] The container state acquisition unit 201 acquires the distribution c(x, y) of the composition c, the distribution ρ(x, y) of the density ρ, and the distribution s(x, y) of the shape s of the substance 102 in the container by referring to the database 210 using the surface state of the substance 102 in the container acquired by the surface measurement device 401. That is, for each two-dimensional position (x, y) of the storage container 101, the container state acquisition unit 201 acquires the composition c, the density ρ, and the shape s corresponding to the surface state of the substance 102 in the container by using the substance information registered in the database 210.

[0055] The distribution ρ(x, y) of the density ρ can be acquired by referring to the database 210 without using the X-ray source 502 and the X-ray detector 503. In this embodiment, it is assumed that the distribution ρ(x, y) of the density ρ is acquired by referring to the database 210.

[0056] When the surface state of the substance 102 in the container acquired by the surface measurement device 401 is not registered in the database 210, the container state acquisition unit 201 sets the distribution ρ(x, y) of the density ρ of the substance 102 in the container to the distribution ρ(x, y) acquired by using the X-ray source 502 and the X-ray detector 503. Alternatively, the container state acquisition unit 201 assumes that the density ρ of the substance 102 in the container is constant for the two-dimensional position (x, y) of the storage container 101, and from the mass M of the substance 102 in the container measured by the mass meter 504, subtracts the mass M' of the substance 102 in the container registered in the database 210 (i.e., the mass M' of the radioactive waste already stored in the storage container 101), and uses the value (M - M'), and from the total volume V of the substance 102 in the container, subtracts the volume V' of the substance 102 in the container registered in the database 210, and uses the value (V - V') to obtain the distribution ρ(x, y) of the density ρ of the substance 102 in the container according to Equation (3). ρ(x,y)=(M - M’) / (V - V’) (3) Equation (3) represents the density ρ (a density with a constant distribution) of a substance whose mass and volume are unknown.

[0057] When the container state acquisition unit 201 determines that the surface state of the substance 102 in the container obtained using the surface measurement device 401 is not registered in the database 210, the distribution c(x, y) of the composition c and the distribution s(x, y) of the shape s of the substance 102 in the container are considered unknown.

[0058] The physical information estimation unit 202 will be described with reference to FIGS. 7 to 9.

[0059] The physical information estimation unit 202 estimates the average height z inside the container and the atomic number ratio H / U of hydrogen to uranium from the distribution c(x, y) of the composition c, the distribution ρ(x, y) of the density ρ, the distribution s(x, y) of the shape s, and the distribution h(x, y) of the height h of the substance 102 in the container obtained by the container state acquisition unit 201. The average height z inside the container and the atomic number ratio H / U of hydrogen to uranium are physical information of the substance 102 in the container and are values necessary for calculating the effective multiplication factor keff of the storage container 101.

[0060] FIG. 7 is a flowchart showing the procedure by which the physical information estimation unit 202 estimates the average height z inside the container.

[0061] In step 701, the physical information estimation unit 202 starts estimating the average height z inside the container.

[0062] In step 702, the physical information estimation unit 202 determines whether there is a non-nuclear fuel substance registered in the database 210 in the substance 102 in the container using the distribution c(x, y) of the composition c. Note that a substance with an unknown composition c, that is, the substance 102 in the container not registered in the database 210, is regarded as a nuclear fuel substance (see step 902 in FIG. 9).

[0063] In step 703, when there is a non-nuclear fuel material registered in the database 210 in the in-container material 102, the physical information estimation unit 202 subtracts the distribution h(x, y) of the height h of this non-nuclear fuel material from the distribution h(x, y) of the height h acquired by the container state acquisition unit 201, and re-determines the distribution h(x, y) of the height h of the in-container material 102. The height h acquired by the container state acquisition unit 201 includes the height h of the non-nuclear fuel material. Since the height h of the non-nuclear fuel material is unnecessary for calculating the effective multiplication factor keff, it is removed from the distribution h(x, y) of the height h acquired by the container state acquisition unit 201.

[0064] In step 704, the physical information estimation unit 202 calculates the mean value zμ and the standard deviation zσ of the distribution h(x, y) in order to evaluate the variation of the distribution h(x, y) of the height h. The variation of the distribution h(x, y) of the height h is a factor of error when calculating the effective multiplication factor keff of the storage container 101.

[0065] In step 705, the physical information estimation unit 202 calculates the average height z inside the container. When the standard deviation zσ of the distribution h(x, y) of the height h is less than or equal to a threshold value arbitrarily determined in advance, the physical information estimation unit 202 sets the mean value zμ of the distribution h(x, y) as the average height z inside the container. Also, when the standard deviation zσ of the distribution h(x, y) of the height h is greater than the above threshold value, the physical information estimation unit 202 sets the sum (zμ + kzσ) of the mean value zμ and the standard deviation zσ of the distribution h(x, y) as the average height z inside the container. However, k is an integer of 1 or more (k = 1, 2, 3,..), and is a value specified by the user so that the error of the calculated effective multiplication factor keff falls within the allowable range.

[0066] In step 706, the physical information estimation unit 202 ends the estimation of the average height z inside the container.

[0067] FIG. 8 is a diagram showing an example of a non-nuclear fuel material 801 existing in the in-container material 102. FIG. 8 shows, as an example, an example in which the non-nuclear fuel material 801 is a structure (for example, a pipe) in a nuclear facility. Such a non-nuclear fuel material 801 is the in-container material 102 registered in the database 210.

[0068] The height h obtained by the container state acquisition unit 201 is the height h including the height h1 of the non-fuel material. The height h1 of the non-fuel material is unnecessary for calculating the effective multiplication factor keff. Therefore, in step 703 of the flowchart shown in FIG. 7, when the non-fuel material 801 registered in the database 210 exists in the material 102 in the container (that is, when the material 102 in the container includes the non-fuel material 801 registered in the database 210), the physical information estimation unit 202 subtracts the distribution h1(x, y) of the height h1 of this non-fuel material from the distribution h(x, y) of the height h obtained by the container state acquisition unit 201 to re-determine the distribution h(x, y) of the height h of the material 102 in the container.

[0069] In this embodiment, it is assumed that the non-fuel material 801 is a pipe and the non-fuel material 801 is placed on the material 102 in the container. The non-fuel material 801 that is a pipe has a known diameter r, and the diameter r is registered in the database 210 together with the surface state. In this embodiment, it is assumed that the distribution h1(x, y) of the height h1 of the non-fuel material is constant with respect to the two-dimensional position (x, y) of the storage container 101, and is approximated as equal to the diameter r of the non-fuel material 801 that is a pipe (h1(x, y) = r) for handling.

[0070] When the non-fuel material 801 registered in the database 210 exists in the material 102 in the container and the non-fuel material 801 is placed on the material 102 in the container, the physical information estimation unit 202 re-determines the distribution h(x, y) of the height h of the material 102 in the container according to Equation (4). h(x,y)=H-d(x,y)-r (4) In Equation (4), as described above, H is the height of the storage container 101 (the distance from the top to the bottom surface), and d(x, y) is the distribution d(x, y) of the distance d obtained by the container state acquisition unit 201.

[0071] The distribution h(x, y) obtained by Equation (4) is, referring to Equation (1), the distribution h1(x, y) (= r) of the height h1 of the non-nuclear fuel material subtracted from the distribution h(x, y) of the height h acquired by the container state acquisition unit 201.

[0072] Figure 9 is a flowchart showing the procedure by which the physical information estimation unit 202 estimates the atomic number ratio H / U of uranium and hydrogen.

[0073] In step 901, the physical information estimation unit 202 starts estimating the atomic number ratio H / U of uranium and hydrogen.

[0074] In step 902, the physical information estimation unit 202 assumes that the substance with an unknown distribution c(x, y) of the composition c is a nuclear fuel material.

[0075] In step 902, the physical information estimation unit 202 refers to the distribution s(x, y) of the shape s and determines whether water and substances other than water can be distinguished in the substance 102 in the container. When the distribution s(x, y) of the shape s is unknown or sandy (Figure 1A), the physical information estimation unit 202 determines that water and substances other than water cannot be distinguished in the substance 102 in the container.

[0076] In step 904, when water and substances other than water can be distinguished in the substance 102 in the container, the physical information estimation unit 202 calculates a rough volume ratio of water and the nuclear fuel material using the distribution c(x, y) of the composition c.

[0077] The physical information estimation unit 202 can obtain the distribution of the substances (including the nuclear fuel material) contained in the substance 102 in the container at the two-dimensional position (x, y) of the storage container 101 based on the distribution c(x, y) of the composition c. The physical information estimation unit 202 determines the position of the water surface of the storage container 101 and the size of the nuclear fuel material from the distribution c(x, y) of the composition c and the image of the substance 102 in the container captured by the surface measurement device 401 (for example, an optical camera). Next, the physical information estimation unit 202 calculates a rough volume ratio of water and the nuclear fuel material using the obtained data and the shape and size of the storage container 101.

[0078] Then, the physical information estimation unit 202 calculates the atomic number ratio H / U of hydrogen to uranium from the calculated volume ratio of water to the nuclear fuel material using Avogadro's constant. The atomic number ratio H / U of hydrogen to uranium is the atomic number ratio throughout the storage container 101.

[0079] In step 905, the physical information estimation unit 202 ends the estimation of the atomic number ratio H / U of hydrogen to uranium. If the water and substances other than water cannot be identified in step 903, the physical information estimation unit 202 directly ends the estimation of the atomic number ratio H / U of hydrogen to uranium.

[0080] Referring to FIG. 10, the criticality margin evaluation unit 203 will be described.

[0081] The criticality margin evaluation unit 203 obtains the effective multiplication factor keff of the storage container 101 from the average height z inside the container and the atomic number ratio H / U of hydrogen to uranium estimated by the physical information estimation unit 202. Then, the criticality margin evaluation unit 203 estimates the criticality margin from the effective multiplication factor keff.

[0082] FIG. 10 is a flowchart showing the procedure in which the criticality margin evaluation unit 203 obtains the effective multiplication factor keff and estimates the criticality margin.

[0083] In step 1001, the criticality margin evaluation unit 203 starts the estimation of the criticality margin.

[0084] In step 1002, the criticality margin evaluation unit 203 obtains the effective multiplication factor keff of the storage container 101. The criticality margin evaluation unit 203 obtains the effective multiplication factor keff according to a known method. That is, the criticality margin evaluation unit 203 uses the average height z inside the container and the atomic number ratio H / U of hydrogen to uranium estimated by the physical information estimation unit 202 and the following known formula (5) or formula (6) to obtain the effective multiplication factor keff.

[0085] In step 1003, the criticality margin evaluation unit 203 estimates the criticality margin. The criticality margin evaluation unit 203 obtains the difference between the calculated effective multiplication factor keff and the value of the effective multiplication factor at which criticality occurs (=1), and estimates this difference as the criticality margin.

[0086] In step 1004, the criticality margin evaluation unit 203 finishes estimating the criticality margin.

[0087] In step 1002, when the shape of the storage container 101 is cylindrical, the criticality margin evaluation unit 203 obtains the effective multiplication factor keff using Equation (5), and when the shape of the storage container 101 is rectangular, it obtains the effective multiplication factor keff using Equation (6). keff = νΣf / {Σa + D(2.405 / R) 2 + (π / z) 2} (5) keff = νΣf / [Σa + D{(π / x) 2 + (π / y) 2 + (π / z) 2}] (6) In Equations (5) and (6), ν is the average number of neutrons released per nuclear fission, Σf is the fission cross-section, Σa is the total absorption cross-section, D is the diffusion coefficient, R is the inner diameter of the storage container 101, and z is the average height inside the container. In Equation (6), x, y, and z are the lengths of three mutually perpendicular sides (width, depth, height) inside the storage container 101.

[0088] The average number of neutrons ν released per nuclear fission, the fission cross-section Σf, the total absorption cross-section Σa, and the diffusion coefficient D are values that depend on the atomic number ratio H / U of uranium and hydrogen. The criticality margin evaluation unit 203 calculates these values by particle transport simulation using the ratio H / U calculated by the physical information estimation unit 202. When the physical information estimation unit 202 cannot calculate the ratio H / U (when the physical information estimation unit 202 does not execute step 904 in FIG. 9), the criticality margin evaluation unit 203 sets the most conservative value for the ratio H / U (i.e., the value at which uranium nuclear fission is most likely to occur), and performs particle transport simulation using this ratio H / U.

[0089] In step 1002, the criticality margin evaluation unit 203 obtains the effective multiplication factor keff assuming that the composition c of the substance 102 in the container is all nuclear fuel material (uranium).

[0090] Also, in step 1002, the criticality margin evaluation unit 203 may obtain the effective multiplication factor keff by performing a particle transport simulation without using formula (5) or formula (6). By performing the particle transport simulation, the criticality margin evaluation unit 203 can obtain the effective multiplication factor keff and evaluate the criticality margin even when the physical information estimation unit 202 cannot estimate the ratio H / U.

[0091] In the criticality margin estimation device and the criticality margin estimation method according to this embodiment, the container state acquisition unit 201 acquires the surface state of the substance 102 (radioactive waste) in the container, and refers to the database 210 to acquire information about the composition c, density ρ, and shape s of the substance 102 in the container using this surface state. Thereby, even when the composition c of the substance 102 in the container is unknown, information about the substance 102 in the container can be acquired without performing destructive analysis such as elemental analysis, and the criticality margin of the substance 102 in the container can be estimated.

[0092] According to the criticality margin estimation device and the criticality margin estimation method according to this embodiment, even when the burnup of the nuclear fuel material stored in the storage container 101 is different, or when non-nuclear fuel materials such as neutron absorbers and moisture are mixed into the storage container 101, the criticality margin can be estimated. In this embodiment, by estimating the criticality margin, the criticality of the nuclear fuel material stored in the storage container 101 can be appropriately managed, and thus the following effects can also be obtained. The first effect is that as much nuclear fuel material as possible can be stored in the storage container 101, so the number of required storage containers 101 can be reduced, and the cost of storing the storage containers 101 can be reduced. The second effect is that when performing a pretreatment to reduce the effective multiplication factor keff such as drying the inside of the storage container 101, the conditions required for the pretreatment can be relaxed by appropriately evaluating the effective multiplication factor keff of the storage container 101, and the time required for the pretreatment can be shortened compared to the prior assumption. The third effect is that since the storage containers 101 can be stored with the distance between the storage containers 101 smaller than the prior assumption, the space for storing the storage containers 101 can be saved.

[0093] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above embodiments have been described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to the embodiments having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Further, the configuration of another embodiment can be added to the configuration of one embodiment. Also, a part of the configuration of each embodiment can be deleted, or other configurations can be added or replaced.

Explanation of Reference Numerals

[0094] 101...storage container, 102...material inside the container, 102a...sand-like material inside the container, 102b...lump material inside the container, 102c...material inside the container registered in a database, 201...container state acquisition unit, 202...physical information estimation unit, 203...criticality margin evaluation unit, 204...criticality margin display unit, 210...database, 211...input unit, 401...surface measuring device, 402...remotely operated manipulator, 403...radioactive waste, 502...X-ray source, 503...X-ray detector, 504...mass meter, 801...non-nuclear fuel material.

Claims

1. A container state acquisition unit that acquires the state of the substance inside the container, which is radioactive waste stored in a storage container; A physical information estimation unit that estimates physical information of the substance inside the container from the state of the substance inside the container acquired by the container state acquisition unit; A critical margin evaluation unit that obtains the effective multiplication factor of the storage container from the physical information of the substance inside the container estimated by the physical information estimation unit, and estimates the critical margin, which is the margin until the substance inside the container reaches criticality, from the effective multiplication factor; A database that stores the surface state, composition, density, and shape of substances that can be the substance inside the container; Comprising; The state of the substance inside the container includes the surface state, composition, density, shape, and height of the substance inside the container; The physical information of the substance inside the container is the average height inside the container, which is the average height of the substance inside the container in the state stored in the storage container, and the atomic number ratio of uranium to hydrogen; A critical margin estimation device characterized by the above.

2. The container state acquisition unit includes a surface measurement device; The surface measurement device measures the surface state of the substance inside the container and the distance from the top of the storage container of the substance inside the container; The container state acquisition unit obtains the height from the distance; The container state acquisition unit obtains the composition, density, and shape by referring to the database using the surface state obtained using the surface measurement device; The critical margin estimation device according to Claim 1.

3. The physical information estimation unit estimates the average height inside the container and the atomic number ratio using the composition, density, shape, and height of the substance inside the container acquired by the container state acquisition unit; The critical margin estimation device according to Claim 1.

4. The critical margin evaluation unit obtains the effective multiplication factor from the average height inside the container and the atomic number ratio estimated by the physical information estimation unit, and sets the difference between the obtained effective multiplication factor and the value of the effective multiplication factor at which criticality occurs as the critical margin; The critical margin estimation device according to Claim 1.

5. The physical information estimation unit estimates the average height inside the container using the average value and standard deviation of the distribution of the height of the substance inside the container acquired by the container state acquisition unit in the two-dimensional position on the plane parallel to the bottom surface of the storage container; The critical margin estimation device according to Claim 3.

6. A critical margin display unit that displays the effective multiplication factor and the critical margin obtained by the critical margin evaluation unit. The critical margin estimation device according to claim 1.

7. A container state acquisition step of acquiring a state regarding a substance in a container, which is radioactive waste stored in a storage container; A physical information estimation step of estimating physical information of the substance in the container from the state regarding the substance in the container acquired in the container state acquisition step; A critical margin evaluation step of obtaining an effective multiplication factor of the storage container from the physical information of the substance in the container estimated in the physical information estimation step, and estimating a critical margin, which is a margin until the substance in the container reaches criticality, from the effective multiplication factor; characterized by including; The state regarding the substance in the container includes the surface state, composition, density, shape, and height of the substance in the container; The physical information of the substance in the container is the average height in the container of the substance in the container in the state stored in the storage container and the atomic number ratio of uranium to hydrogen; In the container state acquisition step, The surface state of the substance in the container and the distance from the top of the storage container of the substance in the container are measured by a surface measurement device; The height is obtained from the distance; The composition, density, and shape are obtained by referring to a database that stores the surface state, composition, density, and shape for substances that can be the substance in the container, using the surface state acquired by the surface measurement device; In the physical information estimation step, the average height in the container and the atomic number ratio are estimated using the composition, density, shape, and height of the substance in the container acquired in the container state acquisition step; A critical margin estimation method characterized by the above.

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