A device for measuring multiplicity of neutrons in different measuring cavities 3 He counter tube selection method

Abstract

The application relates to the field of nuclear radiation detection, in particular to a neutron multiplicity measuring device in different measuring cavities 3 He tube matching method. The technical problem to be solved by the application is to provide a neutron multiplicity measuring device in different measuring cavities 3 He tube matching method, under the premise of meeting the size requirement of the measuring cavity and the detection efficiency, 3 He counting tube length, quantity, interval distance and layout mode, and the total amount of the counting tube is minimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nuclear radiation detection, in particular to a neutron multiplicity measuring device in different measuring cavities 3 He counter tube selection method BACKGROUND

[0002] With the development of nuclear industry, uranium and plutonium materials are increasing in the world, and preventing nuclear proliferation has become a common concern of the international community. Since uranium and plutonium materials can produce fission neutrons, using neutron detection technology and combining with isotope abundance for non-destructive analysis is the most commonly used means in the field of nuclear safeguards. The development of nuclear radiation detection technology makes neutron measurement technology an important means in the field of non-destructive analysis technology in nuclear radiation detection technology, which has important significance in the field of nuclear safeguards, especially in nuclear material accounting.

[0003] Neutrons have the characteristics of strong penetration and difficulty in shielding. In the analysis of high-density and large-volume samples, it is the only feasible and rapid detection technology that can meet the detection technology, and also has broad application prospects in the classification and detection of low-level radioactive waste. In the accurate quantitative analysis of U / Pu materials in the above related fields, including conventional sample analysis, warehouse inventory, U / Pu production line closed accounting, etc., this technology plays an active role.

[0004] Neutron multiplicity measurement technology is a rapid NDA technology that can accurately quantify nuclear materials by measuring the multiplicity distribution of fission neutrons. The measurement process does not require calibration of standard samples, thereby avoiding the influence of standard sample use on the measurement results. Fission neutrons have correlation in time, and the number of neutrons released by a fission event has a certain probability distribution, i.e. multiplicity distribution. This method can distinguish fission neutrons from non-fission neutrons, minimize the interference of non-fission neutrons and the influence of matrix materials on measurement, and neutron multiplicity measurement can be represented by the following equation:

[0005] (1)

[0006] (2)

[0007] (3)

[0008] where , and are the one-, two-, and three-fold count rates, , and are the first, second, and third factorial moments of the spontaneous fission emission neutron number distribution, , ,and These are the first, second, and third factorial moments of the induced fission emission neutron number distribution, respectively. ε It refers to the detector's neutron detection efficiency. , These are the detector's double and triple coincidence gate factors, respectively. The growth coefficient is... This is the ratio of the number of neutrons to the number of neutrons generated during spontaneous fission. denoted as the average reaction rate during spontaneous fission of neutrons.

[0009] To ensure that neutron multiplexing measurement technology can meet the practical needs of different measurement objects, the neutron multiplexing measurement device needs to be designed according to the volume of the object to be measured and the required detection efficiency. When neutron multiplexing measurement devices meet the same or similar main structure, electronic system, and measurement cavity requirements, the main factor affecting the detection efficiency is the detection components. 3 The selection of the He counter tube, namely the positive correlation between its length and the detection efficiency, and 3 The configuration structure of the He-counting tubes, namely the spacing and layout, was then simulated using MCNPX to obtain the number of detected neutrons, verifying whether the detection efficiency could meet the requirements, and determining the appropriate level of efficiency based on the verification results. 3 The selection scheme for He counter tubes. Therefore, it is necessary to study a neutron multiplicity measurement device with different measurement cavities. 3 The He counter tube selection method can meet the needs of rapid selection. Summary of the Invention

[0010] The technical problem to be solved by the present invention is: to provide a neutron multiplicity measurement device with different measurement cavities. 3 The selection method for He counter tubes, under the premise of meeting the requirements of measurement cavity size and detection efficiency, determines... 3 The length, number, spacing, and layout of the counting tubes should be optimized to minimize the total number of counting tubes used.

[0011] The concept and technical solution of this invention are described below:

[0012] Step 1: Determine the size of the measurement cavity and the neutron detection efficiency ε The requirement is to determine the goal of minimizing the total number of counting tubes used;

[0013] Step 2: Determine the diameter of the measuring cavity. 3 The range of the number of He counter tubes, and the selection of the range of values ​​for the number. 3 The number of He counting tubes;

[0014] Step 3: Determine the height of the measuring cavity. 3The range of values ​​for the length of the He counter tube, and the selection within the range of length values. 3 He count tube length;

[0015] Step 4: Confirm 3 The He counter tube can be selected in a layout mode, and one layout mode can be selected from the available layout modes;

[0016] Step 5: Confirm 3 The range of values ​​for the He counter tube spacing is selected, and the range of values ​​for the spacing is determined. 3 The spacing of the He counter tubes;

[0017] Step 6: Based on the selected 3 The length, number, spacing, and layout of the He counter tubes are determined using MCNP simulation to assess whether the detection efficiency meets the requirements. If it does, the proposed scheme is output; otherwise, adjustments are made. 3 The length, number, spacing, and layout of the He counter tubes were determined, and then MCNP simulation was used to judge whether the detection efficiency met the requirements until the obtained scheme met the detection efficiency. ε Requirements.

[0018] Step 7: Output to meet detection efficiency ε The requirements, and 3 He used the method with the least amount of material as the size of the measuring cavity. 3 He counter tube selection scheme.

[0019] The specific implementation steps are as follows:

[0020] Step S1: Determine the required size of the measurement cavity, A×B, where A is the diameter of the measurement cavity and B is the height of the measurement cavity, and determine the detection efficiency δ. ε The required value;

[0021] Step S2, establish 3 The objective function and constraint condition function of the He counter tube selection method

[0022] (4)

[0023] in, for 3 The length of the He counter tube, for 3 The number of He counting tubes, The detection efficiency value is calculated through MCNP simulation;

[0024] Step S3: Determine the diameter of the measuring cavity. 3 The number range of He counter tubes is [ N l , Nh ], wherein, N l is the lower limit of the number of counters , N h is the upper limit of the number of counters , N i is the value of the number of counters per time;

[0025] Step S4, according to the size of the measurement cavity, first determine 3 the value range of the length of the He counter is L l , L h ], wherein, L l is the lower limit of the length of the counter, and L l = B, L h is the upper limit of the length of the counter, and 2B≥ L h > B, L i is the value of the length of the counter per time;

[0026] Step S5, according to 3 the diameter of the He counter, first determine 3 the value range of the spacing of the He counter is d l , d h ], wherein, d l is the lower limit of the spacing of the counter, taking d l = 1, d h is the upper limit of the spacing of the counter taking d h = 10, d i is the value of the spacing of the counter per time;

[0027] Step S6, determine the set of optional layout methods ;

[0028] Step S7, respectively , , as input items combination input MCNP model, and through MCNP simulation, determine whether the detection efficiency meets the requirements, if there are , determine the spacing and layout method in the input item, and go to step S8, if Then, increase the upper limit of the number of counting tubes and the upper limit of the length of counting tubes by 10% respectively, and proceed to step S7, letting... i =1;

[0029] Step S8, will , N l , d i As a definite input item, and,

[0030] (5)

[0031] If Then output And proceed to step S11, if Then let i = i +1, and return to S8, if Then let i =1 Proceed to step S9;

[0032] Step S9, will , , d i As a definite input item, and,

[0033] (6)

[0034] If Then output And proceed to step S11, if Then let i = i +1, and switch back to S9, if Then let i =2 Proceed to step S10;

[0035] Step S10, will , d i As a definite input item, and,

[0036] (7)

[0037] (8)

[0038] If Then output And proceed to step S11, if Then let i = i +1, and switch back to S10;

[0039] Step S11, end.

[0040] Preferably, the step S4, according to the size of the measuring cavity, first determines 3 The length of the He counter tube ranges from L l , L h ], wherein, L l is the lower limit of the length of the counter tube, and L l =B, L h is the upper limit of the length of the counter tube, and L h =1.25B, L i is the value of the length of the counter tube each time;

[0041] The superiority of the present application compared with the prior art is that the present application provides a neutron multiplicity measuring device for different measuring cavities 3 He counter tube selection method, the present application fully considers 3 The positive correlation between the length and number of He counter tubes and the neutron multiplicity measurement detection efficiency, and the nonlinearity of the spacing and layout mode and the neutron multiplicity measurement detection efficiency, determines the detection efficiency ε According to the requirements of the national standard or the actual needs, with the goal of minimizing the total amount of counter tubes used, the counter tube selection scheme that meets the relevant requirements can be quickly and effectively determined, and a feasible method for different measuring cavities is provided. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Neutron multiplicity measuring device 3 He counter tube selection method flow chart DETAILED DESCRIPTION

[0043] The following will be combined with the drawings Figure 1 , the neutron multiplicity measuring device for different measuring cavities 3 He counter tube selection method will be described in detail, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. In the following description, a lot of specific details are described in order to fully understand the present application, but the present application can also be implemented in other ways different from the description, and those skilled in the art can make similar generalization without departing from the connotation of the present application, therefore, the present application is not limited by the specific embodiments disclosed below.

[0044] The calculation method of the present application comprises the following steps:

[0045] Step S1: Determine the required size of the measurement cavity (40cm × 40cm) and determine the detection efficiency. =30%;

[0046] Step S2, establish 3 The objective function and constraint condition function of the He counter tube selection method

[0047] (10)

[0048] in, for 3 The length of the He counter tube, for 3 The number of He counting tubes, The detection efficiency value is calculated through MCNP simulation;

[0049] Step S3: Determine the diameter of the measuring cavity. 3 The number range of He counter tubes is [ N l , N h ],in, N l The lower limit of the number of counting tubes , N h The upper limit of the number of counting tubes , N i The value representing the number of counter tubes used each time;

[0050] Step S4: Based on the size of the measuring cavity, first determine... 3 The range of values ​​for the length of the He counter tube is [ L l , L h ],in, L l This is the lower limit of the counting tube length, and L l =40, L h This is the upper limit of the length of the counting tube, and L h =50, L i The value for the length of the counting tube is determined each time;

[0051] Step S5, according to 3 The diameter of the counting tube must be determined first. 3 The range of values ​​for the He counter tube spacing is [ d l , d h ],in,d l = 1 for the lower limit of the counter tube spacing, d l = 1, d h = 10 for the lower limit of the counter tube spacing, d h = 10, d i = 1 for the counter tube spacing of each time;

[0052] Step S6, determine the set of optional layout methods ;

[0053] Step S7, input the MCNP model as input items respectively , , , , , by combining, and simulate by MCNP, wherein the detection efficiency of has , determine the spacing and layout method in the input items, and go to step S8;

[0054] Step S8, take double ring, 25, 5.5 as the determined input items, and,

[0055] (11)

[0056] has and , let i = 1, go to step S9;

[0057] Step S9, take double ring, 40, 5.5 as the determined input items, and,

[0058] (12)

[0059] has and , let i = 2, go to step S10;

[0060] Step S10, take , d i as the determined input items, and,

[0061] (13)

[0062] (14)

[0063] when If yes then output As a 40cm x 40cm measurement cavity neutron multiplicity measurement device 3 The He counter tube is selected, and the process goes to step S11

[0064] Step S11, end.

[0065] The above embodiments are provided only for the purpose of describing the present application, and are not intended to limit the scope of the present application. Various equivalent substitutions and modifications made without departing from the spirit and principles of the present application should be included in the scope of the present application.

Claims

1. A device for measuring the multiplicity of neutrons in different measuring cavities 3 A method for selecting a He counter tube, characterized in that The method comprises the following steps: Step S1, determine the size requirement φAxB of the measurement cavity, where A is the diameter of the measurement cavity and B is the height of the measurement cavity, determine the requirement value of the detection efficiency δ ε ; Step S2, establishing 3 Objective function and constraint function of He counter tube selection method min L x N stε≥δ ε wherein L is 3 He counter tube, N is 3 He counter tube, and ε is the detection efficiency value calculated by MCNP simulation; Step S3: determining the number of He counter tubes according to the diameter of the measuring cavity 3 The number of He counter tubes ranges from [N l , N h ], wherein N l is the lower limit of the number of counter tubes N h is the upper limit of the number of counter tubes N i is the value of the number of counter tubes each time; Step S4, according to the size of the measuring cavity, first determine 3 The length of the He counter tube is in the range of [L l , L h ], wherein L l is the lower limit of the length of the counter tube, and L l = B, L h is the upper limit of the length of the counter tube, and 2B≥L h >B, L i is the length of the counter tube each time. Step S5, according to 3 He counter tube diameter, first determine 3 He counter tube spacing range is [d l , d h ], wherein, d l For the lower limit of the counter tube spacing, d l = 1, d h For the upper limit of the counter tube spacing, d h = 10, d i For the value of the counter tube spacing each time; Step S6, determining a set of optional layout methods {p 1,...j} ; Step S7, input the <p j ,N h ,L h ,d l >, <p j ,N h ,L h ,(d l +d h ) / 2>, <p j ,N h ,L h ,d h > as input item combination into the MCNP model, and simulate through MCNP to determine whether the detection efficiency meets the requirements, if there is ε≥δ ε , determine the spacing and layout method in the input item, and go to step S8, if ε<δ ε , increase the upper limit of the number of counters and the upper limit of the length of the counters by 10% respectively, and go to step S7, let i=1; Step S8, p j , N l , d i as the determination input, and, If there is ε ≥ δ ε , then output <p j , N l , L i , d i > and go to step S11, if ε < δ ε , then let i = i + 1 and go back to S8, if L i ≥ L h , then let i = 1 and go to step S9; Step S9, p j , L l , d i as the determination input, and, If there is ε ≥ δ ε , then output <p j , N i , L l , d i > and go to step S11, if ε < δ ε , then let i = i + 1 and go back to S9, if N i ≥ N h , then let i = 2 and go to step S10; Step S10, p j , d i as a determination input item, and, If there is ε ≥ δ ε , then output <p j , N i , L i , d i > and go to step S11, if ε < δ ε , then let i = i + 1 and go back to S10; Step S11, end.

2. A device for measuring the multiplicity of neutrons in different cavities according to claim 1 3 Method for selecting a He counter tube, characterized in that The step S4 is to determine the length of the counter tube according to the size of the measuring cavity 3 The length of the counter tube is in the range of [L l , L h ], wherein L l is the lower limit of the length of the counter tube, and L l = B, L h is the upper limit of the length of the counter tube, and L h = 1.25B, and L i is the length of the counter tube each time.

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