Method for calculating upper limit of impurity content of nuclear material in fusion device

Abstract

The application discloses a method for calculating the upper limit of impurity content of nuclear materials of a fusion device, and is used for analyzing the impurity control requirement of materials serving in the nuclear environment of the fusion device. The method is characterized in that: under the service environment conditions and examination requirements of the specified nuclear materials, the main components and the possible impurity elements contained in the materials are simulated, and the control requirement of the impurity elements is determined according to the nuclear response calculation of various normalization indexes. The method can realize the rapid calculation of the upper limit of impurity content of the nuclear materials of the fusion device under the service conditions, and can be applied to the design analysis of the nuclear materials of the fusion device and the fusion device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear engineering, and mainly relates to a fusion device nuclear material impurity content upper limit calculation method. BACKGROUND

[0002] A large amount of high-energy neutrons with energy up to 14.06 MeV are generated by a nuclear fusion device during operation. Nuclear materials are irradiated by high-intensity high-energy neutrons in the service environment of the nuclear device, resulting in the activation of the materials and the generation of radioactive products. These radioactive activation products emit a large amount of gamma photons and a small amount of neutrons through decay after the nuclear device is shut down, generating secondary radioactivity and releasing heat. In order to ensure the radiation safety of the nuclear device and the environment, and to ensure the safety of the operating personnel and the public during the operation and shutdown of the device, it is necessary to select appropriate materials during the design stage of the nuclear device and strictly control the activation of the elements, so that the radioactivity of the activated nuclear materials can be reasonably controlled as low as possible.

[0003] The selection of nuclear materials and the control of impurities need to consider the service environment of the materials, including particle type, energy distribution, irradiation intensity and irradiation time, and also need to consider the post-processing requirements of different materials, so that the radioactivity of the nuclear materials can be reasonably controlled as low as possible, and the generation of radioactivity and its harm to personnel and the environment can be minimized. Therefore, impurity control analysis of various materials for different components of the nuclear device involves a large amount of complex and tedious nuclear analysis calculations. SUMMARY

[0004] To solve the above technical problems, the application discloses a fusion device nuclear material impurity content upper limit calculation method. By performing activation calculation on the main components of the material and each element that may be contained under the specified service environment conditions and examination requirements of the nuclear material, and according to the nuclear response, the contribution index of each element to the examination requirement is calculated, so as to determine the control requirement of the impurity element. This method can realize the rapid impurity content upper limit calculation of the nuclear material under its service conditions, and can be applied to the design analysis of the nuclear material and the nuclear device, and has important engineering value for the optimization of the radiation protection design of the nuclear device.

[0005] To achieve the above purpose, the application is implemented by the following technical scheme:

[0006] A fusion device nuclear material impurity content upper limit calculation method, comprising the following steps:

[0007] Step 1) For a specified nuclear material, perform activation calculation according to its service conditions to obtain its nuclear response;

[0008] Step 2) According to the examination index of the nuclear material and the nuclear response obtained in step 1), calculate the normalized contribution index of each element to the examination index;

[0009] Step 3) Calculate the upper limit of each element component according to the total contribution index of each element.

[0010] Further, in the step 1), the composition of the nuclear material is divided into main components and impurity components;

[0011] The impurity component is a non-design component, which is derived from the raw materials and the manufacturing process of the nuclear material;

[0012] The service condition of the nuclear material includes irradiation condition and irradiation scheme; wherein, the irradiation particle of the nuclear material is neutron, and the irradiation condition is neutron flux rate information; the irradiation scheme is irradiation time and cooling time arrangement information of the nuclear material under different irradiation conditions;

[0013] The activation calculation refers to the process of establishing and solving the burnup equation according to the composition and service condition of the nuclear material, according to the nuclear reaction cross-section data and decay data;

[0014] The nuclear response refers to the material composition change, radioactivity, heat release rate, and dose rate information of the nuclear material after being activated by neutrons, and does not include surface contamination caused by radioactivity contamination.

[0015] Further, in the step 1, the activation calculation is performed on the main components and possible impurity components of the nuclear material, and if the possible impurity components are uncertain, all naturally occurring elements in the periodic table are scanned and calculated.

[0016] Further, the neutron flux rate information is obtained by particle transport calculation and is given in the form of multi-group flux. For example, the neutron flux rate of a fusion device can be given in the form of VITAMIN-J 175 group multi-group neutron flux rate, or CCFE-709 group neutron flux rate published by the UK Kalame Fusion Research Center.

[0017] Further, for a fusion device running in a pulse mode, the irradiation scheme is to homogenize and simplify the irradiation scheme before the last operating day, and only the last operating day is calculated in a pulse mode; the homogenization and simplification is to keep the total neutron yield and total irradiation time unchanged, and to adjust the neutron flux level to the total neutron yield divided by the total irradiation time, so as to equivalent the pulse operation mode to the steady-state operation mode.

[0018] Further, in the step 2),

[0019] The evaluation index of the nuclear material includes radioactive waste classification management requirements and nuclear device shutdown maintenance requirements;

[0020] The post-processing requirements of the nuclear material are determined by the maintenance scheme during the shutdown maintenance of the nuclear device in which the material is served, and the disassembly, pretreatment, hot cell temporary storage, and preparation requirements of the nuclear material after the nuclear device is decommissioned, and specifically include the specific limits of the radioactivity specific activity, contact dose rate, decay heat, and content of specific radionuclides of the material at different examination time nodes;

[0021] The nuclear response changes over time, and the examination index of the nuclear material is the level requirement of the nuclear response at one or more examination time nodes.

[0022] Further, in the step 2),

[0023] The radioactive waste classification management requirements of the nuclear material are determined according to the radiation safety and radioactive waste management principles of the International Atomic Energy Agency and various countries, and are determined by the types, total amounts, specific activities, and decay heat of radionuclides and the radioactive characteristics.

[0024] In step 2, the radioactivity of the nuclear material changes over time, which is caused by the natural decay of radionuclides, and does not include the changes of radionuclides caused by nuclide separation and other operations.

[0025] Further, the examination time nodes are determined by the operation and maintenance cycle of the fusion device.

[0026] Further, in the step 2),

[0027] The contribution index of a specific element to a specific examination index at a specific examination time node is determined by summing the nuclear responses of the activated product nuclides of the specific element at the examination time node divided by the upper limit value of the examination index requirement; and the calculation formula is Where i is the activated product nuclide of the specific element e, R e,t,i is the nuclear response of the nuclide i at the examination time node t under the examination index l, L i is the upper limit value of the examination index l for the nuclide i;

[0028] The total contribution index of the specific element to the examination index is determined by the maximum value of the contribution index of the element at different examination time nodes under all examination indexes.

[0029] Further, in the step 3),

[0030] The upper limit of the element composition is determined by the total contribution index of the element to the examination requirement, and the calculation formula is min(100%, 100% / Index(e)×f); where Index(e) is the total contribution index of the element e, and f is a multi-impurity correction factor for correcting the influence when the nuclear material contains multiple impurities, and is taken as 0.1-0.3;

[0031] If the total contribution index of the main component element e of the nuclear material is greater than 1, it indicates that the main component element e itself causes the nuclear material to fail to meet the examination requirements.

[0032] Through the above technical solution, the upper limit of the impurity content of the nuclear material of the fusion device is calculated, and the impurity control requirement of the nuclear material is given.

[0033] The advantages of the present application are:

[0034] (1) The present application can quickly calculate the impurity control requirement of the nuclear material of the fusion device, which is beneficial to the optimization of the nuclear material research and development.

[0035] (2) The present application can give a warning prompt for the main component of the nuclear material that does not meet the examination requirements.

[0036] (3) The present application can scan and analyze all possible elements when the impurity type is not specified.

[0037] (4) The present application can specify the irradiation scheme, operation and maintenance scheme, and examination requirements, so as to reasonably achieve the lowest device radioactivity. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The present application is a method for calculating the upper limit of the impurity content of the nuclear material of a fusion device. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0040] The present application discloses a method for calculating the upper limit of the impurity content of the nuclear material of a fusion device. The method simulates the activation of the main components and possible impurity elements of the material under the specified service environment conditions and examination requirements of the nuclear material, and calculates various normalization indexes according to the nuclear response, so as to determine the control requirements of the impurity elements.

[0041] Figure 1 The present application shows the implementation steps of a method for calculating the upper limit of the impurity content of the nuclear material of a fusion device. The present application simulates the activation of the main components and possible elements of the material under the specified service environment conditions and examination requirements of the nuclear material, and calculates the contribution indexes of the elements to the examination requirements according to the nuclear response, so as to determine the control requirements of the impurity elements. After all the required calculations are completed, the control requirements of the elements of the nuclear material are given in the form of the periodic table of elements.

[0042] Specifically, the upper limit of impurity content of nuclear material in a fusion device is calculated by the following steps:

[0043] Step 1, for a specified nuclear material, activation calculation is performed according to its service condition to obtain its nuclear response.

[0044] According to the user-provided fusion device design scheme and material composition, the multi-group neutron flux of the nuclear material service environment is obtained by solving the neutron transport equation of the fusion device by the Monte Carlo particle transport or deterministic method. The user provides the irradiation scheme of the fusion device and the possible impurity composition of the material. If no possible impurity composition is provided, all naturally occurring elements are considered as possible impurities. Then, the user uses the activation calculation software to simulate and calculate the nuclear response of all element compositions of the material at the examination time point. For example, the main components of a low-activation material include Fe, Cr, W, V, Ta, and Mn. To examine the upper limit of the content of different impurity elements when the main components are determined, the material is applied to a certain fusion device, and the radioactivity level of the material under certain irradiation conditions meets the examination requirements of the contact dose rate or the radioactivity waste level. Using the neutron flux level of the service site of the material and the irradiation scheme of the device, the activation calculation is performed on the main components and all impurity elements to obtain the activation response at the examination time point.

[0045] Step 2, according to the nuclear material examination index and the nuclear response, the contribution index of each element to the examination index is calculated.

[0046] The user uses the formula to calculate the contribution index of each element to different examination indexes at different examination time points, and takes the maximum value as the total contribution index. For example, the examination index includes two items, which are the material contact dose rate of 12 days after shutdown not exceeding 10 mSv / h and the clean control level after 100 years of shutdown, i.e. the clean control index is less than or equal to 1. The contact dose rate of a certain element at 12 days after shutdown is 5 mSv / h, which contributes 0.5 to the examination index, and the clean control index after 100 years of shutdown is 0.1, which contributes 0.1 to the examination index. The total contribution index of the element is the maximum value of the contribution values of different examination indexes, i.e. 0.5. Step 3, according to the total contribution index of each element, the upper limit of each element composition is calculated;

[0047] The user controls the upper limit calculation formula of the element as min (100%, 100% / Index (e) x f). Wherein, f is a multi-impurity correction factor, used for correcting the influence when the nuclear material contains multiple impurities, and can be taken as 0.1-0.3. If the total contribution index of the main component element of the material is greater than 1, it indicates that the element itself causes the nuclear material to fail to meet the examination requirements. For example, if the total contribution index of a certain impurity element is 5.0, the technical scheme gives the upper limit of the element mass fraction as 0.06% according to min (100%, 100% / 5x0.3), and the multi-impurity correction factor here is 0.3. Through the above technical scheme, the upper limit of the impurity content of the nuclear material of the fusion device can be calculated, and the impurity control requirements of the nuclear material are given. The part not described in detail in the present application belongs to the known technology in the art.

[0048] Although the above describes the specific embodiments of the present application in a descriptive manner, so as to facilitate the understanding of the present application by those skilled in the art. But it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the scope of the appended claims and the spirit and scope of the present application, these changes are obvious, and are within the protection of the present application.

Claims

1. A method for calculating an upper limit of an impurity content of a nuclear material in a fusion device, characterized by, The method comprises the following steps: Step 1) performing activation calculation on the specified nuclear material according to its service condition to obtain its nuclear response; Step 2) calculating the normalized contribution index of each element to the examination index according to the nuclear material examination index and the nuclear response obtained in step 1); Step 3) calculating the upper limit of the composition of each element according to the total contribution index of each element; The activation calculation refers to the process of establishing and solving the burnup equation according to the composition of the nuclear material and the service condition, according to the nuclear reaction cross-section data and the decay data; The nuclear response refers to the material composition change, radioactivity, heat release rate, and dose rate information of the nuclear material after being activated by neutrons, and does not include surface contamination caused by radioactivity contamination; In step 2), The contribution index of a specific element to a specific evaluation index at a specific evaluation time node is determined by summing the nuclear responses of each activated product nuclide of the specific element at the evaluation time node divided by the upper limit value of the evaluation index requirement; the calculation formula is where i is an activated product nuclide of a specific element e, is the nuclear response of nuclide i at the evaluation time node t under the evaluation index l, is the upper limit value of the evaluation index l for nuclide i; The total contribution index of the specific element to the examination index is determined by the maximum value of the contribution index of the specific element at different examination time nodes under all examination indexes; In step 3), The upper limit of the element composition is determined by the total contribution index of the element to the examination requirements, and the calculation formula is ; wherein, the total contribution index of the element e, is a multi-impurity correction factor, used to correct the influence when the nuclear material contains multiple impurities, and is 0.1-0.3; If the total contribution index of the main component element e of the nuclear material is greater than 1, it indicates that the main component element e itself causes the nuclear material to fail to meet the examination requirements.

2. The method for calculating the upper limit of the impurity content of the nuclear material of the fusion device according to claim 1, wherein: In step 1), the composition of the nuclear material is divided into main components and impurity components; The impurity components are non-design components and are derived from the raw materials and the manufacturing process of the nuclear material; The service condition of the nuclear material includes irradiation condition and irradiation scheme; wherein the irradiation particle of the nuclear material is neutron, and the irradiation condition is neutron flux rate information; the irradiation scheme is the irradiation time and cooling time arrangement information of the nuclear material under different irradiation conditions.

3. The method for calculating the upper limit of the impurity content of the nuclear material of the fusion device according to claim 2, wherein: In step 1, the activation calculation is performed on the main components and possible impurity components of the nuclear material, and if the possible impurity components are uncertain, all naturally occurring elements in the periodic table are scanned and calculated.

4. The method for calculating the upper limit of the impurity content of the nuclear material of the fusion device according to claim 2, wherein: The neutron flux rate information is obtained by particle transport calculation and is given in the form of multi-group flux.

5. The method for calculating the upper limit of the impurity content of the nuclear material of the fusion device according to claim 2, wherein: For the fusion device running in pulse mode, the irradiation scheme is to homogenize and simplify the irradiation scheme before the last operation day, and only the last operation day is calculated in pulse mode; the homogenization and simplification is to adjust the neutron flux level to the total neutron yield divided by the total irradiation time, so as to equivalent the pulse operation mode to the steady-state operation mode.

6. The method for calculating the upper limit of the impurity content of the nuclear material of the fusion device according to claim 1, wherein: In step 2), The examination index of the nuclear material includes the requirements for the classification management of radioactive waste and the requirements for the shutdown maintenance of the nuclear device; The reprocessing requirements for nuclear materials are determined by the maintenance plan for the nuclear device in service during shutdown maintenance and the requirements for dismantling, preprocessing, hot cell storage, and preparation of nuclear materials after the decommissioning of the nuclear device; specifically, this includes restrictions on the specific activity, exposure dose rate, decay heat, and content of specific radionuclides of the materials at different assessment time points. The nuclear response changes over time, and the assessment indicators for the nuclear material are the required nuclear response levels at one or more assessment time points.

7. The method for calculating the upper limit of impurity content in nuclear materials of a fusion device according to claim 6, characterized in that: In step 2), The requirements for the classification and management of radioactive waste of nuclear materials are determined by the type, total amount, specific activity, and decay heat radioactivity of the radionuclides, and are based on the radiation safety and radioactive waste management principles of the International Atomic Energy Agency and various countries.

8. The method for calculating the upper limit of impurity content in nuclear materials of a fusion device according to claim 6, characterized in that: The assessment timeframe is determined by the operation and maintenance cycle of the fusion device.

Images