A method for designing a proton accelerator aperture through radiation shielding

Abstract

The application provides a kind of proton accelerator hole penetration radiation shielding design method, including establishing the model of proton bombardment target nucleus, the dose rate distribution field in the secondary particle transport process is counted by virtual grid technology, simultaneously, using weight window generator obtains weight window lower limit parameter file;According to the dose field distribution, the weight window lower limit parameter and the source bias parameter are obtained, so that the dose rate at the hole position and the dose rate distribution based on the grid technology are obtained using the parameters, and the hole penetration radiation shielding design is carried out;The dose rate calculation for the outside of the penetration pipeline of strong electricity, weak electricity, heating, water supply and drainage, process system and equipment in the radiation shielding design of proton accelerator can be realized, the collaborative design of multiple penetrations is realized, the economy and efficiency of shielding design are improved, and the radiation shielding analysis and design of proton accelerator hole penetration are efficiently and reasonably completed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radiation protection, and particularly relates to a design method for a proton accelerator hole penetration radiation shield. BACKGROUND

[0002] Radiation shield design is the key design and focus of industrial proton accelerators, medical proton therapy accelerators, isotope production proton accelerators and other proton accelerator systems. A large number of shield body structures, labyrinth body structures, high-energy shielding materials, and penetration hole shields are used in the radiation shield design. The safety and rationality of the design directly affect the radiation safety of radioactive workers and the public.

[0003] In the radiation shield design of a proton accelerator, the shield design and analysis of the penetration hole are the most complex and difficult. The reasons are mainly as follows: 1) There are many types, quantities and sizes of penetration holes, mainly including strong electricity, weak electricity, heating and ventilation, water supply and drainage, process systems and equipment, and the size ranges from a few centimeters to a few hundred centimeters in diameter; 2) The forms of pipe wall penetration are complex, commonly used are straight wall penetration, inclined wall penetration, U-shaped wall penetration, Z-shaped wall penetration and S-shaped wall penetration. The traditional analysis method of the radiation shield of the proton accelerator hole penetration mainly analyzes the dose rate through theoretical formula and designs the size, position and penetration mode of the hole penetration in detail. However, it is difficult to analyze the dose rate outside the wall penetration through the theoretical formula due to the complexity of the penetration, which cannot accurately design and analyze the hole penetration mode to meet the requirements of the regulations and standards.

[0004] For the complex pipe penetration radiation shield design, a particle transport program based on the Monte Carlo method is mainly used for analysis. The Monte Carlo method observes and analyzes the behavior of a large number of neutrons, and estimates the value of the estimator by statistical averaging method. The particle transport program based on the Monte Carlo method can accurately describe the geometric model and source term, and has high robustness by using continuous cross section. However, the calculation efficiency is low and the calculation time is long. The radiation shield calculation of pipe penetration using the Monte Carlo program belongs to the problem of small probability deep penetration, and the particles sampled from the source term have only a small probability of being transported to the outside of the wall. There are mainly three methods to solve this problem: 1) increasing the sample, which will exponentially increase the calculation time, and is not completely feasible, with low efficiency improvement; 2) calculation mode, by selecting the forward transport mode or the accompanying transport mode according to the calculation and analysis of the working condition; this method also faces the problem of small probability deep penetration and cannot completely solve the problem; 3) efficient acceleration method, to develop and select a reasonable acceleration method to increase the efficiency of program calculation and analysis.

[0005] At present, there is no efficient acceleration method for the Monte Carlo program to analyze the radiation shielding of the proton accelerator hole penetration. Therefore, how to efficiently and reasonably complete the radiation shielding analysis and design of the proton accelerator hole penetration is a technical problem to be solved. SUMMARY

[0006] The present application provides a kind of proton accelerator hole penetration radiation shielding design method, can realize the dose rate calculation of the outside of penetration pipeline in the radiation shielding design of proton accelerator for strong electricity, weak electricity, warm and hot, water supply and drainage, process system and equipment, accurately analyzes the dose rate outside penetration, greatly improves the design efficiency and precision of hole penetration, realizes the collaborative design of multiple penetrations, improves the economy of shielding design.

[0007] According to some embodiments, the present application adopts the following technical solutions:

[0008] The present application provides a kind of proton accelerator hole penetration radiation shielding design method, comprising:

[0009] Obtain the model parameters of proton bombardment target nucleus under the hole penetration radiation shielding and establish the model of proton bombardment target nucleus;

[0010] Under the model of proton bombardment target nucleus, one-step proton, neutron, photon and electron coupling transport is carried out to realize the physical simulation of proton bombardment target nucleus, and the transport process of secondary particles in the containing medium is carried out;

[0011] The dose rate distribution field in the transport process of secondary particles is counted by virtual grid technology, and the weight window lower limit parameter file is obtained by using weight window generator;

[0012] The dose field distribution is obtained according to formula one and formula two to obtain the weight window lower limit parameter and source bias parameter, and the one-step particle transport simulation of the model of proton bombardment target nucleus is carried out to obtain the dose rate at hole position and the dose rate distribution based on grid technology, if the dose rate at hole position is obtained Convergence, the dose rate at hole position is used for hole penetration radiation shielding design.

[0013] Compared with the prior art, the present application has the following advantages:

[0014] The application adopts a proton accelerator channel penetration radiation shielding design method, establishes a model of proton bombarding target nucleus, and carries out secondary particle transport in medium, and through virtual grid technology, dose rate distribution field in the secondary particle transport process is counted, and at the same time, a weight window lower limit parameter file is obtained by using a weight window generator; the dose field distribution is obtained according to formula one and formula two to obtain the weight window lower limit parameter and the source bias parameter, and the model of proton bombarding target nucleus is simulated by one-step particle transport, the dose rate at the channel position and the dose rate distribution based on the grid technology are obtained, if the dose rate at the channel position is obtained, the dose rate at the channel position is used for channel penetration radiation shielding design, the dose rate calculation of the external penetration pipeline of strong electricity, weak electricity, heating, water supply and drainage, process system and equipment and the like in the proton accelerator radiation shielding design can be realized, the external dose rate is accurately analyzed, the design efficiency and precision of channel penetration are greatly improved, the collaborative design of multiple penetrations is realized, the economy of shielding design is improved, and the radiation shielding analysis and design of proton accelerator channel penetration are efficiently and reasonably completed.

[0015] Advantages of the additional aspects of the application will be partially given in the following description, partially become obvious from the following description, or be understood by the practice of the application.

[0016] In order to make the above-mentioned purpose, features and advantages of the application more obvious and easy to understand, the following preferred embodiments are specifically described, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings accompanying the specification of the application are used to provide further understanding of the application, the schematic embodiments of the application and the description thereof are used to explain the application, and do not constitute improper limitation on the application.

[0018] Figure 1 A schematic diagram of the proton accelerator channel penetration radiation shielding design method. DETAILED DESCRIPTION

[0019] The application will be further described below in combination with the drawings and embodiments.

[0020] It should be pointed out that the following detailed description is all exemplary, and is intended to provide further explanation of the application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the application belongs.

[0021] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0022] Embodiment one:

[0023] As shown in the formula one and the formula two, the embodiment provides a method for designing a proton accelerator channel penetrating radiation shield, comprising: Figure 1

[0024] obtaining model parameters of a proton bombardment target nucleus under the channel penetrating radiation shield and establishing a model of the proton bombardment target nucleus;

[0025] using a Monte Carlo program to perform one-step proton, neutron, photon and electron coupling transport under the model of the proton bombardment target nucleus to realize physical simulation of the proton bombardment target nucleus and to perform a transport process of secondary particles in a medium;

[0026] statistically obtaining a dose rate distribution field in the transport process of the secondary particles by using a virtual grid technology, and simultaneously obtaining a weight window lower limit parameter file by using a weight window generator;

[0027] calculating the dose field distribution into a weight window lower limit parameter and a source bias parameter according to the formula one and the formula two, inputting the weight window lower limit parameter into the weight window lower limit parameter file, using the file to perform one-step particle transport simulation on the model of the proton bombardment target nucleus, obtaining a dose rate at a channel position and a dose rate distribution based on the grid technology, and if the dose rate at the channel position converges, using the dose rate to design the channel penetrating radiation shield.

[0028] Further, if the dose rate at the channel position does not converge, using the dose field distribution obtained by using the latest model of the proton bombardment target nucleus to obtain a weight window lower limit parameter according to the formula one and the formula two, inputting the weight window lower limit parameter into the weight window lower limit parameter file, and iteratively using the same until the dose rate at the channel position converges.

[0029] The step of obtaining the model parameters of the proton bombardment target nucleus under the channel penetrating radiation shield and establishing the model of the proton bombardment target nucleus comprises: establishing the model of the proton bombardment target nucleus and the models of the shielding space, the shielding wall and the channel penetration according to an application scenario, and specifically, a Monte Carlo program can be used to build a model by using a text or a three-dimensional visual modeling program.

[0030] As an implementation mode, the grid division of the weight window and the grid division of the dose rate obtained by using the weight window generator are consistent. ​

[0031] As an implementation, the generation of the weight window lower limit parameter and the source bias parameter is based on a dose response accelerated calculation method of Monte Carlo forward transport, and the mathematical model is as follows:

[0032]

[0033]

[0034] In the formula, w th (r, E): weight window lower limit parameter; SI: smoothing factor; ∑: average cross section of dose rate detection response; r: position; E: energy; R: dose rate; q bias : source bias parameter; q0: initial source distribution.

[0035] Specifically, the proton accelerator aperture penetration radiation shielding analysis method can realize one-step direct analysis of secondary particles such as neutrons and photons generated by proton hitting a target, and the transport process of protons and the secondary particles in a medium.

[0036] Specifically, the method comprises the following steps:

[0037] According to the application scenario, a model of proton bombardment of a target nucleus and a model of shielding space, shielding wall and aperture penetration are established, and through coupled transport of protons, neutrons, photons and electrons, dose rate is obtained by using grid statistics. Using the obtained dose rate distribution, the weight window acceleration parameter is constructed, and then Monte Carlo particle transport is performed using the obtained weight window parameter to obtain a relatively accurate dose rate result. Thus, according to the accurate dose rate calculation result, the aperture penetration radiation shielding design of the proton accelerator is realized.

[0038] The dose response accelerated calculation method and process based on Monte Carlo forward transport for the aperture penetration of the proton accelerator mainly comprises the following steps:

[0039] Step 1: According to the application scenario, a model of proton bombardment of a target nucleus and a model of shielding space, shielding wall and aperture penetration are established.

[0040] Step 2: One-step coupled transport of protons, neutrons, photons and electrons is performed for the model to realize the physical simulation process of proton bombardment of a target nucleus and the process of generating secondary particles such as secondary neutrons and secondary photons, and the transport process of the secondary particles in a medium containing air and concrete.

[0041] Step 3: For the particle transport process in the previous step, the dose rate distribution field is statistically obtained by using a virtual grid technology. At the same time, a weight window lower limit parameter file is obtained by using a weight window generator. The grid division of the weight window is consistent with the grid division of the dose rate.

[0042] Step 4: Using the obtained dose field distribution, the optimized weight window lower limit parameter is obtained according to formula (I), the source bias parameter is obtained using formula (II), and the optimized weight window lower limit parameter is written into the weight window lower limit parameter file format obtained in step 3.

[0043] Step 5: Using the optimized weight window lower limit parameter file and the source bias parameter obtained in step 4, the one-step particle transport simulation in step 2 is performed to obtain the dose rate at the channel position and the dose rate distribution based on the grid technology.

[0044] Step 6: If the dose rate at the channel penetration position obtained does not converge, the new grid dose rate distribution obtained in step 5 is used to repeat steps 4 and 5 until the dose rate at the channel position converges and meets the shielding design requirements.

[0045] Preferably, the dose response acceleration calculation method based on Monte Carlo forward transport for proton accelerator channel penetration in the second step, the third step, the fourth step, the fifth step, and the sixth step has the following main features:

[0046] Feature 1: Grid consistency;

[0047] The grid division scheme of the weight window parameter based on the grid technology in the method is consistent with the grid division scheme of the dose rate distribution based on the grid technology. In media such as air, where the mean free path of particles is relatively long, the size of the grid can be relatively large; in media such as concrete, where the mean free path of particles is relatively small, the size of the grid can be relatively small.

[0048] Feature 2: Grid-based weight window parameter generation technical scheme;

[0049] This technical scheme takes into account the contribution of neutrons and photons of different energies and different positions to the dose rate outside the channel penetration. By introducing the multi-group flux dose conversion coefficients of multi-group neutrons and photons as the coefficients of the contribution of neutrons and photons of different energies to the dose rate.

[0050] Feature 3: Smoothing coefficient;

[0051] For the case where the adjacent grid weight window parameter changes significantly and has a large gradient, a smoothing coefficient SI with a value range of 0.0-1.0 is introduced. After introducing the smoothing coefficient, the transport of neutrons and photons in the air medium and the concrete medium inside the channel penetration will not cause excessive calculation resource consumption due to excessive splitting.

[0052] Feature 4: Iterative optimization scheme;

[0053] For the case that the external dose rate of the aperture penetration cannot converge by using the one-step method of the dose response acceleration calculation method based on the Monte Carlo forward transport for the proton accelerator aperture penetration, the use of multiple iterations can improve the convergence of the external dose rate.

[0054] Preferably, the Monte Carlo particle transport program in the second step, the fifth step and the sixth step needs a program with weight window technology, and it is particularly preferred to have a weight window technology based on grid technology.

[0055] The specific embodiments of the application are described above with reference to the accompanying drawings, but are not a limitation on the scope of protection of the application, and those skilled in the art should understand that various modifications or changes made by those skilled in the art on the basis of the technical solutions of the application without creative labor are still within the protection scope of the application.

Claims

1. A method of designing a proton accelerator beam-penetration radiation shield, the method comprising: The application relates to a method for establishing a radiation shielding analysis model of a channel, and a radiation shielding analysis method of the channel. The method comprises the following steps: a model of a proton bombarding a target nucleus is established; a one-step proton, neutron, photon and electron coupling transport is carried out under the model of the proton bombarding the target nucleus to realize physical process simulation of the proton bombarding the target nucleus and to carry out secondary particle transport in a medium; a dose rate distribution field in the secondary particle transport process is counted by using a virtual grid technology, and a weight window lower limit parameter file is obtained by using a weight window generator; the grid division of the weight window and the grid division of the dose rate are consistent; (Formula One) (Equation Two) In the formulae: w th (r, E): weight window lower limit parameter; weight window lower limit parameters and source bias parameters are obtained according to the dose field distribution, the obtained weight window lower limit parameters are input into the weight window lower limit parameter file, and a mathematical model is as follows: : smoothing factor; ∑: average cross section of the dose rate probe response; r : position; E : energy; R : dose rate; q bias : source bias parameter; q 0: initial source distribution; SI 2. The method of designing a proton accelerator channel penetrating radiation shield according to claim 1, wherein, a model of the proton bombarding the target nucleus is established, one-step particle transport simulation is carried out, a dose rate at a channel position and a dose rate distribution based on a grid technology are obtained, and if the dose rate at the channel position converges, the dose rate at the channel position is used for channel radiation shielding design. The dose field distribution is obtained by using a dose response acceleration calculation method based on a Monte Carlo forward transport according to formula I.

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