A method and device for calculating transmuted silicon distribution in aluminum alloy heavy water tank

Abstract

A method and a computing device for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank belong to the field of nuclear engineering. The method for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank comprises the following steps: first, a reactor model is provided, and a three-dimensional particle transport model is established based on the reactor model using a Monte Carlo program; a three-dimensional neutron-photon coupled particle transport calculation is performed in combination with the reaction cross sections and response functions of neutrons with Al‑27, Al‑28 and Si‑28; the spatial distribution of the (n, γ) reaction rate of Al‑27, the spatial distribution of the total absorption reaction rate of Al‑27, the spatial distribution of the total absorption reaction rate of Al‑28, and the spatial distribution of the total absorption reaction rate of Si‑28 are calculated; finally, the transmutation yield and spatial distribution of silicon in the aluminum alloy heavy water tank are calculated. The method can calculate the accurate spatial distribution of transmuted silicon and improve the simulation accuracy of the quantitative evaluation of neutron irradiation damage in aluminum alloy heavy water tanks. The present invention also provides a computing device.

Description

Technical Field

[0001] The invention belongs to the field of nuclear engineering, and in particular relates to a method and a computing device for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank. Background Art

[0002] For heavy water research reactors, the heavy water tank is the physical boundary of heavy water and one of the most important equipment in the research reactor. A large number of vertical irradiation channels are arranged inside it. Due to the complex structure of the heavy water tank, limited installation environment space, and high radioactivity after irradiation, it is relatively difficult to replace the heavy water tank during the design life cycle. The irradiation safety of the research reactor heavy water tank is the cornerstone to ensure the safe operation of the research reactor throughout its life cycle. The life of the heavy water tank directly affects and determines the operation and life of the research reactor.

[0003] In the design of heavy water tanks made of aluminum alloy, fast neutrons, medium energy neutrons and thermal neutrons can all cause transmutation damage to aluminum. With the increase of thermal neutron injection, the content of silicon produced by transmutation in the aluminum alloy matrix continues to increase, and the change of silicon-containing precipitation phase in the microstructure will have a significant impact on the performance of the aluminum alloy. Silicon produced by transmutation is one of the main mechanisms leading to irradiation damage to heavy water tanks in research reactors.

[0004] However, it has the following main disadvantages: 1) The ignition consumption program can only analyze the transmuted silicon production at one point, and cannot calculate the transmuted silicon distribution on the inner wall of the heavy water tank, and cannot consider the influence of the geometric structure on the transmuted silicon. 2) The consumption library in the ignition consumption program is generally a normalized single group cross section, which has a certain uncertainty. 3) The cross-sectional data energy group structure used in the ignition consumption program has only a limited number of groups, which cannot achieve high-precision calculation and analysis of transmuted silicon production.

[0005] In the radiation damage analysis of the heavy water tank of the research reactor, it is necessary not only to accurately quantify the transmutated silicon production during the operation of the research reactor, but also to obtain the field distribution of the transmutated silicon to determine the maximum radiation damage position of the heavy water tank during the life cycle. Therefore, it is necessary to establish a new evaluation method to accurately and quantitatively analyze the transmutated silicon production and field distribution. Summary of the invention

[0006] The purpose of the present invention is to provide a method for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank, and to accurately calculate the amount and spatial distribution of transmuted silicon. The present invention also provides a calculation device.

[0007] According to an embodiment of one aspect of the present invention, a method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank is provided, the method comprising the following steps:

[0008] Step a): providing a reactor model, wherein the reactor model includes a reactor structure model, and the model parameters should at least include the arrangement, structural dimensions and material composition of the core fuel assembly, control rod assembly, heavy water tank, heavy water, light water coolant and reactor internals, core power and power distribution, and fission neutron energy spectrum;

[0009] Step b): Based on the reactor model, a three-dimensional particle transport model is established using a Monte Carlo program;

[0010] Step c): Based on the three-dimensional particle transport model, combined with the reaction response functions of neutrons with Al-27, Al-28 and Si-28, three-dimensional neutron-photon coupled particle transport calculation is performed;

[0011] Step d): According to the calculation results of step c), the spatial distribution of (n, γ) reaction rate of Al-27, the spatial distribution of total absorption reaction rate of Al-27, the spatial distribution of total absorption reaction rate of Al-28 and the spatial distribution of total absorption reaction rate of Si-28 are calculated;

[0012] Step e): According to the calculation results of step d), the amount and spatial distribution of transmuted silicon in the aluminum alloy heavy water tank are calculated.

[0013] This method can obtain the distribution of transmuted silicon yield and the transmuted silicon yield at different radial and axial positions on the inner wall of the heavy water tank; the continuous energy cross section is used in the Monte Carlo program to perform particle transport analysis and reaction rate calculation, eliminating the influence of insufficient refinement of the energy group structure of the cross-sectional data on the accuracy of the calculation results; the refined neutron injection rate is directly coupled with the continuous energy cross section to obtain the accurate reaction rate.

[0014] Furthermore, in some embodiments, in step a), the reactor structure model includes the spatial distribution of the structure and material composition of the core fuel assembly, the control rod assembly, the aluminum alloy heavy water tank, heavy water, light water and in-core components.

[0015] Furthermore, in some embodiments, in the step a), the reactor structure model also includes the temperatures of the heavy water and the light water.

[0016] Furthermore, in some embodiments, in the step c), the three-dimensional neutron-photon coupled particle transport calculation is calculated based on the three-dimensional core power distribution and the continuous energy cross section.

[0017] Furthermore, in some embodiments, in the step e),

[0018] ;

[0019] Where N is Avogadro's constant, is the neutron reaction cross section of Al-27 to form Al-28, is the total neutron absorption cross section of Al-27, is the total neutron absorption cross section of Al-28, is the total neutron absorption cross section of Si-28, A 0 is the atomic weight of Al-27, A(t) is the specific activity, is the neutron injection rate, t is the irradiation time, x, y, z are the spatial coordinates, is the Si-28 decay constant, is the Al-28 decay constant, The fraction of Al-28 that decays into Si-28.

[0020] According to an embodiment of another aspect of the present invention, there is provided a computing device, which includes a memory and a processor, wherein the memory stores a computing program, and when the computing program is executed by the processor, the method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank provided in any of the aforementioned embodiments can be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic flow chart of a method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank in one embodiment;

[0022] Figure 2 Schematic diagram of the two-dimensional transmutation silicon field distribution of an aluminum alloy heavy water tank calculated in one embodiment.

[0023] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0025] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0026] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0027] The equipment components in the near-core area of ​​the reactor are in high-irradiation environment conditions for a long time. For equipment that cannot be replaced during its service life, the irradiation safety of the equipment and materials is an important factor affecting the life of the reactor. For research reactors that use aluminum alloy heavy water tanks as the physical boundary of heavy water, the heavy water tanks are one of the most important equipment in the research reactor, and a large number of vertical irradiation channels are arranged inside them. Due to the complex structure of the heavy water tanks, limited installation environment space, and high radioactivity after irradiation, it is difficult to replace the heavy water tanks during the design life. The irradiation safety of the research reactor heavy water tanks is the cornerstone to ensure the safe operation of the research reactor throughout its life. The life of the heavy water tanks directly affects and determines the operation and life of the research reactor. Conducting irradiation safety analysis of the research reactor heavy water tanks is a key factor in determining the design indicators of the research reactor, and it is also an important basis for the research and development of heavy water tank equipment.

[0028] In the design of heavy water tanks made of aluminum alloy, fast neutrons, medium energy neutrons and thermal neutrons can all cause transmutation damage to aluminum. On the one hand, fast neutrons produce gas products such as helium and hydrogen through (n, α) and (n, p) transmutation reactions. On the other hand, neutrons, mainly thermal neutrons, convert aluminum into silicon through continuous reactions. As the thermal neutron irradiation time increases, the silicon content increases synchronously. The precipitated phases (Si and Mg) in the microstructure 2 The structure, size and distribution of Si) will determine the properties of aluminum alloy after irradiation. Si produced by transmutation is one of the main mechanisms leading to irradiation damage to the heavy water tank of the research reactor.

[0029] The material of the inner wall of the heavy water tank of the research reactor is aluminum alloy, and its main material component is Al-27. Al-27 absorbs neutrons to produce (n, γ) reaction to produce Al-28, and Al-28 produces β - Decay produces Si-28. According to the (n,γ) reaction cross section of Al-27, the larger cross section is mainly thermal neutrons and part of the resonance area, while the cross section of fast neutrons is relatively small. The half-life of Al-28 is 2.24 minutes, and its β - The decay produces Si-28 with a decay branching ratio of 100%.

[0030] At present, the traditional heavy water tank silicon transmutation analysis mainly uses the ignition consumption program for calculation, which performs activation analysis of items by solving the fuel consumption equation. This method has a fast calculation speed, and it can quickly calculate the transmuted silicon production at a certain point in the heavy water tank. However, it has the following main disadvantages: 1) The ignition consumption program can only analyze the transmuted silicon production at one point, and cannot calculate the transmuted silicon distribution on the inner wall of the heavy water tank, and cannot consider the influence of the geometric structure on the transmuted silicon. 2) The fuel consumption library in the ignition consumption program is generally a normalized single group cross section, which has a certain uncertainty. 3) The cross-sectional data energy group structure used in the ignition consumption program has only a limited number of groups, and it is impossible to achieve high-precision calculation and analysis of the transmuted silicon production.

[0031] In the irradiation damage analysis of the heavy water tank of the research reactor, it is necessary not only to accurately quantify the transmutated silicon production during the operation of the research reactor, but also to obtain the field distribution of the transmutated silicon to determine the maximum irradiation damage position of the heavy water tank during the life cycle. Therefore, it is necessary to establish a new evaluation method to accurately and quantitatively analyze the transmutated silicon production and field distribution.

[0032] An embodiment of one aspect of the present invention provides a method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank, such as Figure 1 As shown, the method comprises the following steps:

[0033] Step a): Provide a reactor model. The reactor model includes the overall structure of the research reactor core and heavy water tank, and includes corresponding design parameters. The design parameters include at least the arrangement, structural dimensions and material composition of the core fuel assembly, control rod assembly, heavy water tank, heavy water, light water coolant and reactor internals, the total core power and power distribution, fission neutron energy spectrum, etc.

[0034] The calculation process only considers the process of neutrons being generated in the core and then transported to the heavy water tank to undergo nuclear reactions with atoms in other structures. Therefore, the reactor model should reflect the spatial distribution of the neutron source, the neutron energy spectrum, and the spatial distribution of other atoms on the path of neutrons being transported to the heavy water tank. In the modeling process, by establishing a structural model of the reactor and assigning the properties of the relevant materials to the corresponding areas in the model, the spatial distribution of different atoms can be described.

[0035] Step b): Based on the reactor model, a three-dimensional particle transport model is established using a Monte Carlo program, taking into account the geometric structure, material composition and temperature, in which the temperature of heavy water and light water needs to be considered.

[0036] After the distribution states of different atoms in space are given in step a), how to establish a three-dimensional particle transport model using a Monte Carlo program is a method known to those skilled in the art.

[0037] Step c): For the particle transport model obtained in step b), combined with the reaction response functions of neutrons with Al-27, Al-28 and Si-28, three-dimensional core power distribution and continuous energy cross section are used to perform three-dimensional neutron-photon coupled particle transport, and the neutronic parameter information of the aluminum alloy heavy water tank is statistically calculated in the transport calculation.

[0038] Step d): Based on the calculation results of step c), the spatial distribution of the (n,γ) reaction rate of Al-27, the spatial distribution of the total absorption reaction rate of Al-27, the spatial distribution of the total absorption reaction rate of Al-28 and the spatial distribution of the total absorption reaction rate of Si-28 are calculated and analyzed respectively.

[0039] In the production analysis of transmutated silicon in the heavy water tank of the research reactor, the generation and disappearance of Al-27, Al-28 and Si-28 in the neutron field are considered. Al-27 is the parent nucleus, and its generation term does not need to be considered. Its disappearance term is mainly the disappearance due to absorption of neutrons. The generation term of Al-28 is the (n,γ) reaction of Al-27, and the disappearance term mainly includes the decay of Al-28 and the disappearance of Al-28 due to absorption of neutrons. The generation term of Si-28 is the decay of Al-28, and the decay and disappearance of Si-28 due to absorption of neutrons are considered at the same time.

[0040] Step e): Based on the calculation results of step d), calculate the distribution field of transmuted silicon in the aluminum alloy heavy water tank as it changes with time.

[0041] For research reactors using aluminum alloy as the material for heavy water tanks, the main material component of the heavy water tank is Al-27. In the near-core area of ​​the nuclear reactor, Al-27 is affected by neutron radiation and will undergo (n, γ) reaction to produce Al-28, and Al-28 will undergo β - Decay produces Si-28. According to the (n,γ) reaction cross section of Al-27, the larger reaction cross section is mainly thermal neutrons and some resonance regions, while the cross section of fast neutrons is relatively small. The half-life of Al-28 is 2.24 minutes, and its β - The decay produces Si-28, with a decay branching ratio of 100%. Si-28 is a stable nuclide.

[0042] The keys to quantitatively analyzing the production and distribution of transmuted silicon in the aluminum alloy heavy water tank of the research reactor are: 1) particle transport model and material composition; 2) continuous energy cross section; 3) three-dimensional core power distribution; 4) neutron injection rate distribution and nuclear reaction rate distribution related to transmuted silicon; 5) nuclide inventory analysis of transmuted silicon.

[0043] The amount and spatial distribution of transmuted silicon can be calculated using the following formula:

[0044] ,

[0045] The meanings of the symbols are shown in Table 1:

[0046]

[0047] Table 1

[0048] In a preferred embodiment, the two-dimensional distribution field state of transmuted silicon in a side wall of an aluminum alloy heavy water tank simulated and calculated by the above method is as follows: Figure 2 According to the calculation results, the transmuted silicon content of any area in the aluminum alloy heavy water tank changing with time can be obtained.

[0049] The method for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank provided in the above embodiment can be implemented by a computing device provided in an embodiment of another aspect of the present invention. The computing device includes a memory and a processor, wherein the memory stores a transmuted silicon distribution calculation program. When the transmuted silicon distribution calculation program is executed by the processor, the method for calculating the distribution of transmuted silicon in an aluminum alloy heavy water tank provided in any of the above embodiments can be implemented. The computing device can use a general-purpose computer, a specially built dedicated computing device, or a virtual machine or a cloud computing device. The transmuted silicon distribution calculation program can be a Monte Carlo calculation program written in a general-purpose computer language, or it can be modeled and programmed on the basis of existing Monte Carlo method calculation software such as Geant4, MCNP or FLUKA.

[0050] The purpose of the above embodiments is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of the implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank, characterized in that: The following steps are involved: Step a): providing a reactor model, wherein the reactor model includes a reactor structure model, core power and power distribution, fission neutron energy spectrum, structural material composition, and temperature of at least part of the material; Step b): Based on the reactor model, a three-dimensional particle transport model is established using a Monte Carlo program; Step c): Based on the three-dimensional particle transport model, combined with the response functions of neutrons and Al-27, Al-28 and Si-28, three-dimensional neutron-photon coupled particle transport calculation is performed; Step d): According to the calculation results of step c), the spatial distribution of (n, γ) reaction rate of Al-27, the spatial distribution of total absorption reaction rate of Al-27, the spatial distribution of total absorption reaction rate of Al-28 and the spatial distribution of total absorption reaction rate of Si-28 are calculated; Step e): According to the calculation results of step d), the amount and spatial distribution of transmuted silicon in the aluminum alloy heavy water tank are calculated: ； Where N is Avogadro's constant, is the neutron reaction cross section of Al-27 to form Al-28, is the total neutron absorption cross section of Al-27, is the total neutron absorption cross section of Al-28, is the total neutron absorption cross section of Si-28, A0 is the atomic weight of Al-27, A(t) is the specific activity, is the neutron injection rate, t is the irradiation time, x, y, z are the spatial coordinates, is the Si-28 decay constant, is the Al-28 decay constant, The fraction of Al-28 that decays into Si-28.

2. The method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank according to claim 1, characterized in that: In the step a), the reactor structure model includes the structure and spatial distribution of material components of the core fuel assembly, control rod assembly, the aluminum alloy heavy water tank, heavy water, light water and internal components, the total core power and power distribution, and the fission neutron energy spectrum.

3. The method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank according to claim 2, characterized in that: In the step a), the reactor structure model also includes the temperatures of the heavy water and the light water.

4. The method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank according to claim 1, characterized in that: In the step c), the three-dimensional neutron-photon coupled particle transport calculation is performed based on the three-dimensional core power distribution and the continuous energy cross section.

5. A computing device comprising a memory and a processor, characterized in that: The memory stores a calculation program, and when the calculation program is executed by the processor, the method for calculating the transmuted silicon distribution of an aluminum alloy heavy water tank as described in any one of claims 1 to 4 can be implemented.

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