Design method of spherical online neutron spectrometer and neutron spectrometer

Abstract

The invention relates to a spherical online neutron spectrometer design method and a neutron spectrometer, and the design method comprises the following steps: 1, determining design parameters which at least comprise an energy measurement range and an angle response range; step 2, determining the material of the moderated body; step 3, constructing test models of a plurality of neutron spectrometers, wherein the set depths of the detectors among the test models and / or the set numbers of the detectors with the same depth are different; step 4, calculating the energy response of each test model during uniform incidence of 4 pi; 5, determining the set depth and the set number of the detectors according to the calculation result of the energy response of each test model, and obtaining a design model; and 6, modeling according to the design model to obtain a simulation model, verifying whether the simulation model meets the requirements of an energy measurement range and an angle response range, if so, determining that the design model is qualified, and if not, determining that the design model is unqualified. The method can be used for design guidance and is wide in application range.

Description

Technical Field

[0001] The present invention relates to the technical field of neutron energy spectrum measurement, and in particular to a design method of a spherical on-line neutron spectrometer and a neutron spectrometer. Background Art

[0002] With the rapid development of the application of neutron technology in the nuclear industry and the medical industry, higher requirements are put forward for the accurate measurement of neutron dose. Since the interaction mechanism between neutrons and matter is relatively complex, and the dosimetric effect of neutrons is closely related to neutron energy, accurately measuring the neutron energy spectrum is a necessary prerequisite for estimating neutron dose.

[0003] Common neutron energy spectrum measurement devices include multi-sphere neutron spectrometers, time-of-flight spectrometers, recoil proton spectrometers, etc. Among common neutron energy spectrum measurement devices, time-of-flight spectrometers and recoil proton spectrometers are mostly used for laboratory measurements, and both have great limitations and are not suitable for measurements in large-dose situations. Multi-sphere neutron spectrometers can measure neutrons in a relatively wide energy range and are widely used; their main disadvantage is that neutron spheres are usually huge in volume and difficult to carry, and are not suitable for application scenarios with obvious weight restrictions such as space measurements. Multiple neutron spheres are required for measurement to give results, the operation is cumbersome, the measurement time is long, and large errors will be introduced for neutron fields with unstable intensities. The above problems need to be solved urgently. Summary of the Invention

[0004] The present invention discloses a design method of a spherical on-line neutron spectrometer and a neutron spectrometer, aiming to solve the technical problems existing in the prior art.

[0005] The present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a design method of a spherical on-line neutron spectrometer, the on-line neutron spectrometer including a spherical moderator and a detector; characterized in that the design method includes the following steps:

[0007] Step 1, determining design parameters, the design parameters at least including an energy measurement range and an angular response range;

[0008] Step 2, determining the material of the moderator;

[0009] Step 3, constructing test models of multiple neutron spectrometers, the depth at which the detectors are arranged and / or the number of detectors arranged at the same depth being different between the test models;

[0010] Step 4, calculating the energy response of each test model when incident uniformly in 4π;

[0011] Step 5, determining the arrangement depth and the number of the detectors according to the calculation results of the energy responses of each test model to obtain a design model;

[0012] Step 6: Model according to the design model to obtain a simulation model, and verify whether the simulation model meets the requirements of the energy measurement range and the angular response range.

[0013] If it meets the requirements, the design model is qualified.

[0014] If it does not meet the requirements, the design model is unqualified, and repeat Steps 3 to 6 until the simulation model meets the requirements of the energy measurement range and the angular response range.

[0015] In a design method of a spherical online neutron spectrometer according to the present invention, the energy measurement range is 0.01 eV to 15 MeV; and / or, the angular response range is less than or equal to 6%.

[0016] In a design method of a spherical online neutron spectrometer according to the present invention, the material of the moderator is a hydrogen-rich material.

[0017] In a design method of a spherical online neutron spectrometer according to the present invention, the step of calculating the energy response of each test model for 4π uniform incidence includes:

[0018] Select a plurality of equally spaced incident angles within the 4π range at the same depth;

[0019] Calculate the neutron energy response of the test model at each incident angle;

[0020] Perform weighted averaging on the obtained neutron energy responses of the plurality of test models to obtain the energy response of the test model for 4π uniform incidence.

[0021] In a design method of a spherical online neutron spectrometer according to the present invention, the weight factor for weighted averaging is the ratio of the area of the sphere corresponding to the intersection line of the cone with the vertex at the center of the moderator sphere and the sphere where the detector is located to the area of the sphere, and the apex angle of the cone is twice the incident angle.

[0022] In a design method of a spherical online neutron spectrometer according to the present invention, neutrons at the same incident angle include multiple different energy values.

[0023] In a design method of a spherical online neutron spectrometer according to the present invention, the interval of the incident angle is 5 - 30°.

[0024] In a design method of a spherical online neutron spectrometer according to the present invention, the set depth of the detector includes a depth less than or equal to 3 cm and a depth greater than or equal to 4 cm, and the depth is the radial distance from the detector to the surface of the moderator.

[0025] In a design method of a spherical on-line neutron spectrometer according to the present invention, the detectors at the same depth are evenly distributed.

[0026] In a design method of a spherical on-line neutron spectrometer according to the present invention, it further includes the steps of modeling according to the design model to obtain a test model and verifying whether the test model meets the requirements of neutron energy spectrum resolution ability, including:

[0027] Using the parameters of the design model as input items for Monte Carlo modeling;

[0028] Selecting a reference source, and calculating the counts of each detector of the test model at the reference source through Monte Carlo modeling;

[0029] Inverse-solving the neutron energy spectrum based on the counts of each detector through an energy spectrum algorithm;

[0030] Calculating the degree of consistency of the energy spectrum parameters between the neutron energy spectrum and the reference spectrum. If the deviation is less than or equal to 10%, the energy spectrum resolution ability of the test model meets the requirements.

[0031] In a design method of a spherical on-line neutron spectrometer according to the present invention, the steps of verifying whether the test model meets the requirements of the energy measurement range include:

[0032] According to the test model, calculating the energy response function of the test model at different incident angles, and the neutron energy range corresponding to the energy response function includes the energy measurement range;

[0033] For each response function curve, taking the energy range interval corresponding to the response greater than 50% of the peak value of the response function curve;

[0034] Taking the union of the energy intervals corresponding to the responses greater than 50% of the peak value of each curve, and using the upper and lower limits of the union as the lower and upper limits of the energy measurement of the test model;

[0035] Judging whether the lower and upper limits of the energy measurement of the test model meet the requirements of the energy measurement range.

[0036] In a design method of a spherical on-line neutron spectrometer according to the present invention, the steps of verifying whether the test model meets the requirements of the angular response range include:

[0037] Selecting a reference source, calculating the counts of each detector of the test model when measuring the reference source through Monte Carlo modeling, inverse-solving the neutron energy spectrum through an energy spectrum algorithm, and calculating the total neutron fluence;

[0038] Randomly changing the incident direction of the reference source n times within a 4π solid angle range to obtain n sets of the total neutron fluence;

[0039] Calculate the average value and standard deviation of the total fluence results of the n groups of the neutron energy spectra, and divide the standard deviation by the average value as the calculation result of the angular response of the test model;

[0040] Compare the calculation result of the angular response of the test model with the angular response range to determine whether it meets the requirements.

[0041] In a second aspect, the present invention also provides a neutron spectrometer designed by adopting any one of the above design methods, which is characterized by comprising a moderator and a detector;

[0042] The moderator is a spherical structure made of polyethylene material;

[0043] The detectors are arranged at depths less than or equal to 3 cm and greater than or equal to 4 cm from the surface of the moderator, and multiple detectors are arranged at the same depth and are symmetrically arranged.

[0044] In the neutron spectrometer of the present invention, the radius of the moderator is 15 cm; the setting depths of the detectors include 2 cm, 4 cm, 7 cm and 10 cm.

[0045] In the neutron spectrometer of the present invention, the number of detectors arranged at the depths of 2 cm and 4 cm is greater than the number of detectors arranged at the depths of 7 cm and 10 cm.

[0046] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0047] The present invention mainly provides a design method for a spherical online neutron spectrometer. Based on constructing multiple test models, the energy response of multiple different test models is calculated to determine the setting depth and number of detectors, and a design model is obtained. Then, a test model is constructed based on the design model, and the test model is verified. The design model corresponding to the test model that meets the design parameter requirements is used as the parameters of the finally obtained online neutron spectrometer. The technical route of the present invention is clear, and targeted design can be carried out based on different required performances. It has a wide range of applications, especially in the detection of a large energy range, realizing the detection of a larger energy interval range at one time and realizing online measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. These drawings form a part of the present invention. The schematic embodiments of the present invention and their explanations explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0049] Figure 1 It is a schematic structural diagram of the neutron spectrometer designed in the design method of a spherical online neutron spectrometer of the present invention when the incident angle is θ;

[0050] Figure 2 It is the curve graph of response weight factors corresponding to different incident angles in the design method of a spherical on-line neutron spectrometer of the present invention;

[0051] Figure 3 It is one of the response curve graphs of detectors at different depths in the design method of a spherical on-line neutron spectrometer of the present invention;

[0052] Figure 4 It is the second of the response curve graphs of detectors at different depths in the design method of a spherical on-line neutron spectrometer of the present invention.

[0053] Figure 5 It is the energy response curve of the neutron spectrometer in Example 2 of the present invention. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. In the description of the present invention, it should be noted that the term "or" is generally used in the sense of including "and / or", unless otherwise clearly specified in the content.

[0055] Unless clearly specified to the contrary, the numerical parameters in this specification and the appended claims may be approximate values and can be changed according to the required characteristics obtained through the content of the present invention. Specifically, all the numbers representing the contents of components, reaction conditions, etc. used in the specification and claims should be understood to be modified by the term "about" in all cases. Generally, the meaning expressed is that it includes a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, and a change of ±0.5% in some embodiments.

[0056] Furthermore, the word "comprising" does not exclude the existence of materials or steps not listed in the claims. Ordinal numbers such as "first", "second", "third" and Arabic numerals, letters, etc. used in the specification and claims to modify the corresponding elements or steps do not themselves mean the order in the manufacturing method, and the use of these ordinal numbers is only used to clearly distinguish the steps.

[0057] In addition, unless specifically described or steps that must occur in sequence, the order of the above steps is not limited to the above list and can be changed or rearranged according to the required design. And the above embodiments can be used in combination with each other or combined with other embodiments based on considerations of design and reliability, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0058] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0059] To solve the problems existing in the prior art, the embodiments of the present application provide a design method of a spherical on-line neutron spectrometer and a neutron spectrometer.

[0060] Embodiment 1

[0061] This embodiment provides a design method of a spherical on-line neutron spectrometer. The on-line neutron spectrometer includes a spherical moderator and a detector. The design method includes the following steps:

[0062] Step 1: Determine the design parameters, where the design parameters at least include the energy measurement range and the angular response range;

[0063] Step 2: Determine the material of the moderator;

[0064] Step 3: Construct multiple test models of the neutron spectrometer, where the depth of the detector setting and / or the number of detectors set at the same depth are different between the test models;

[0065] Step 4: Calculate the energy response of each test model under 4π uniform incidence, and obtain the energy response of each test model at different incident angles for incident neutrons of the same energy;

[0066] Step 5: Determine the setting depth and the number of the detectors according to the calculation results of the energy responses of each test model to obtain a design model;

[0067] Step 6: Model according to the design model to obtain a test model, and verify whether the test model meets the requirements of the energy measurement range and the angular response range.

[0068] If it meets the requirements, the design model is qualified.

[0069] If it does not meet the requirements, the design model is unqualified, and repeat steps 3 to 6 until the test model meets the requirements of the energy measurement range and the angular response range.

[0070] A design method of a spherical online neutron spectrometer according to the present invention is based on constructing multiple test models, calculating the energy response of multiple different test models to determine the setting depth and quantity of detectors, obtaining a design model, constructing a test model with the design model, and verifying the test model. The design model corresponding to the test model that meets the design parameter requirements is used as the parameters of the finally obtained online neutron spectrometer. The technical route of the present invention is clear, and targeted design can be carried out based on different required performances, with wide applications, especially in the detection of a large energy range, achieving a larger energy range detection at one time and realizing online measurement. Setting the moderator as a sphere can reduce the angular response of the single-sphere neutron spectrometer.

[0071] In some preferred embodiments, according to the calculation results of the energy response of each test model, the setting depth and quantity of the detectors are determined. Obtaining the design model includes calculating the angular response of the test model according to the calculation results of the above-mentioned energy response, and selecting the depth and quantity of the detector design model corresponding to the test model that meets the angular response range requirements as the parameters of the design model.

[0072] In some preferred embodiments, take 6 Li or 10 B nuclide as the detector with the thermal neutron detection medium, such as a coated SiC semiconductor detector, a coated Si semiconductor detector, a doped semiconductor detector or a scintillator detector. The detector of this material has a large neutron nuclear reaction cross-section, and the nuclear nuclide has a high abundance in nature and is easy to obtain. Preferably, select 6 LiF-coated SiC semiconductor detector.

[0073] In some preferred embodiments, the energy measurement range is 0.01 eV to 15 MeV, and this range can be applicable to a variety of application scenarios and has a higher applicable range; and / or, the angular response range is less than or equal to 6%, and under such requirements, the measurement accuracy of the neutron spectrometer can be higher.

[0074] In some preferred embodiments, the material of the moderator is a hydrogen-rich material; the mass of the hydrogen atom is similar to that of the neutron, and the neutron can be well moderated through elastic scattering.

[0075] Preferably, the material of the moderator is polyethylene, boron polyethylene or water. Further preferably, the material of the moderator is polyethylene. The polyethylene material has a high hydrogen density, is easy to obtain and has a low price.

[0076] In some preferred embodiments, the steps of calculating the energy response of each test model for 4π uniform incidence include:

[0077] Select multiple equally spaced incident angles within 4π at the same depth, such as Figure 1 the angle θ in

[0078] Calculate the neutron energy response of the test model at each incident angle;

[0079] Perform weighted averaging on the neutron energy responses of the obtained multiple test models to obtain the energy response of the test model under 4π uniform incidence.

[0080] Among them, the weight factor for weighted averaging is the ratio of the spherical area corresponding to the intersection line of the cone with the center of the moderator sphere as the vertex and the sphere where the detector is located to the spherical area, and the apex angle of the cone is twice the incident angle.

[0081] The specific calculation method is as follows:

[0082] Assume a sphere with a unit radius and an area of 4π. As Figure 2 shown, the probability that the neutron incident angle is θ1 to θ2 under 4π uniform incidence is equal to the area of the spherical surface sandwiched by the two conical surfaces with the endpoints at the center of the sphere and apex angles of 2θ1 and 2θ2 respectively divided by 4π. According to the spherical cap area formula, after derivation, the formula

[0083]

[0084] Discrete values θ1 to θ n are selected within the range of 0 to 180°, a total of n points, and are equally spaced within 0 to 180°. P i represents the probability that the neutron incident angle is closest to θ i . According to (1), there is

[0085]

[0086] Perform convolution on the neutron energy response R(θ) and P i to obtain the response R 4π under 4π uniform incidence.

[0087]

[0088] Preferably, the neutrons with the same incident angle include multiple different energy values. For example, the energy values are selected within the range of 10 -9 to 100 MeV, which can cover the neutron energies commonly used in radiation protection. Preferably, the energy values are logarithmically equally spaced, and the ratio of adjacent energy values is 10 0.1 , which is beneficial to the writing and implementation of the de-spectroscopy algorithm and fully reflects the energy spectrum characteristics of the thermal neutron region, fast neutron region, and intermediate energy region.

[0089] Preferably, in order to reduce the calculation amount and fully reflect the influence of the incident angle on the energy response, the interval of the incident angle is 5 - 30°; more preferably, the interval of the incident angle is 15°.

[0090] In some preferred embodiments, the detector can be set at intervals of 1 cm in depth, that is, at distances of 1 cm, 2 cm... n cm from the surface of the moderator, corresponding to a test model respectively.

[0091] In some preferred embodiments, the set depth of the detector includes depths less than or equal to 3 cm and depths greater than or equal to 4 cm. The depth is the radial distance from the detector to the surface of the moderator. Based on this, the neutron spectrometer can not only respond to neutrons in the low-energy region but also to neutrons in the high-energy region.

[0092] In some preferred embodiments, the detectors at the same depth are evenly distributed. Based on the design principle of even distribution, the angular response can be reduced. Especially when multiple detectors are set at the same depth, the angular response can be further reduced.

[0093] In some preferred embodiments, it also includes steps of obtaining a test model by modeling according to a design model and verifying whether the test model meets the requirements of neutron energy spectrum resolution ability, including:

[0094] Using the parameters of the design model as input items for Monte Carlo modeling;

[0095] Selecting a reference source and calculating the counts of each detector in the test model when the reference source is used through Monte Carlo modeling;

[0096] Inverting the neutron energy spectrum based on the counts of each detector through an energy spectrum algorithm;

[0097] Calculating the degree of consistency between the energy spectrum parameters of the neutron energy spectrum and the reference spectrum. If the deviation is less than or equal to 10%, the energy spectrum resolution ability of the test model meets the requirements.

[0098] In some preferred embodiments, the steps of verifying whether the test model meets the requirements of the energy measurement range include:

[0099] According to the test model, calculating the energy response function of the test model at different incident angles. The neutron energy range corresponding to the energy response function includes the energy measurement range;

[0100] For each response function curve, taking the energy range interval corresponding to the response greater than 50% of the peak of the response function curve;

[0101] Taking the union of the energy intervals corresponding to the responses greater than 50% of the peak of each curve, and using the upper and lower limits of the union as the lower and upper limits of the energy measurement of the test model;

[0102] Judging whether the lower and upper limits of the energy measurement of the test model meet the requirements of the energy measurement range.

[0103] In some preferred embodiments, the steps of verifying whether the test model meets the requirements of the angular response range include:

[0104] Select a reference source, such as 252 Cf source. Obtain the counts of each detector when the test model measures the reference source through Monte Carlo modeling calculation. Inverse solve the neutron energy spectrum through the energy spectrum algorithm, sum the fluence of each point of the neutron energy spectrum, and obtain the total fluence of the neutron energy spectrum;

[0105] Randomly change the incident direction of the reference source n times within the 4π solid angle range to obtain n groups of total fluences of the neutron energy spectrum;

[0106] Calculate the average value and standard deviation of the results of the total fluences of n groups of neutron energy spectra, and divide the standard deviation by the average value as the calculation result of the angular response of the test model;

[0107] Compare the calculation result of the angular response of the test model with the angular response range to determine whether it meets the requirements.

[0108] Experimental example

[0109] Taking a polyethylene spherical moderator with a radius of 15 cm as an example, design the depth and quantity of detector settings;

[0110] 1. Determination of detector setting depth

[0111] Construct 10 test models at depths of 1 cm, 2 cm... 10 cm respectively, and the obtained response curves are as shown in Figure 3 and Figure 4 shown,

[0112] For the energy response curve at each depth position, the energy interval corresponding to the response greater than 90% of the peak value is called the peak region. According to Figure 3 , Figure 4 , the peak region corresponding to a shallower depth is in the low-energy region; as the depth increases, the peak region moves towards the high-energy region; when the depth is 1 - 3 cm, there are obvious differences in the peak region; when the depth is 4 - 10 cm, the peak regions basically coincide and are in the MeV magnitude.

[0113] In order to achieve accurate neutron dose measurement, multiple depths should be selected within the range of 4 - 10 cm. In order to ensure a wide energy measurement range and enhance the detection ability of the single-sphere neutron spectrometer for neutrons in the low-energy region, at least 1 depth needs to be selected within the range less than 3 cm. Considering both factors, 4 depths are preferably selected from 10 depths, which are 2 cm, 4 cm, 7 cm, and 10 cm respectively.

[0114] 2. Determination of the number and position of detectors at each depth

[0115] Considering that the layout of each layer of detectors should have good geometric symmetry, the following 2 alternative schemes are given:

[0116] Scheme 1, with a total of 6 detectors, arranged in the directions shown in the following table.

[0117] Serial number Direction Serial number Direction 1 (1,0，0) 2 (-1,0，0) 3 (0,1,0) 4 (0，-1,0) 5 (0,0,1) 6 (0,0，-1)

[0118] Scheme 2: A total of 14 detectors, arranged in the directions shown in the following table.

[0119] Serial number Direction Serial number Direction 1 (1,0,0) 2 (-1,0,0) 3 (0,1,0) 4 (0,-1,0) 5 (0,0,1) 6 (0,0,-1) 7 (0.58,0.58,0.58) 8 (0.58,0.58,-0.58) 9 (0.58,-0.58,0.58) 10 (0.58,-0.58,-0.58) 11 (-0.58,0.58,0.58) 12 (-0.58,0.58,-0.58) 13 (-0.58,-0.58,0.58) 14 (-0.58,-0.58,-0.58)

[0120] The neutron source is 252 a Cf source. The incident direction is randomly selected with equal probability within a 4π solid angle. The counts of each detector are calculated using Monte Carlo simulation software, and the average count of the detectors in each depth layer is calculated by depth statistics. Sampling is performed 10,000 times, and the standard deviation of the sample of the average count of the detectors in each depth layer is divided by the sample mean to obtain the angular response of the average count of the detectors in that depth layer. The above two schemes are calculated, and the results are as shown.

[0121] The angular responses of different selected depth layers are calculated, and the results are shown in the following table.

[0122] Depth (cm) 2 4 7 10 Scheme 1 12.27 9.7 4.58 0.76 Scheme 2 2.57 1.64 0.53 0.15

[0123] According to the calculation results, the deeper the depth and the more the number of detectors, the smaller the angular response. In order to make the angular response of the spectrometer energy spectrum result less than 6%, it is required that the angular responses of the average counts of the detectors in each depth layer are all less than 6%. To meet this requirement, 14 detectors should be arranged according to Scheme 2 at the shallower depths of 2 cm and 4 cm, and at the deeper depths of 7 cm and 10 cm, using Scheme 1 (6 detectors) can achieve the goal of an angular response less than 6%. Considering the saving of the number of detectors, 6 detectors are arranged according to Scheme 1.

[0124] 3. Determination of the design model of the single-sphere neutron spectrometer

[0125] The configuration scheme of the single-sphere neutron spectrometer is to place a total of 40 6 LiF-coated SiC semiconductor detectors inside a polyethylene sphere with a radius of 15 cm. The central coordinates of the detector positions are shown in the following table (coordinate unit: cm).

[0126] Serial number Detector coordinates Serial number Detector coordinates Serial number Detector coordinates 1 (13,0,0) 15 (11,0,0) 29 (8,0,0) 2 (-13,0,0) 16 (-11,0,0) 30 (-8,0,0) 3 (0,13,0) 17 (0,11,0) 31 (0,8,0) 4 (0,-13,0) 18 (0,-11,0) 32 (0,-8,0) 5 (0,0,13) 19 (0,0,11) 33 (0,0,8) 6 (0,0,-13) 20 (0,0,-11) 34 (0,0,-8) 7 (7.51,7.51,7.51) 21 (6.35,6.35,6.35) 35 (5,0,0) 8 (7.51,7.51,-7.51) 22 (6.35,6.35,-6.35) 36 (-5,0,0) 9 (7.51,-7.51,7.51) 23 (6.35,-6.35,6.35) 37 (0,5,0) 10 (7.51,-7.51,-7.51) 24 (6.35,-6.35,-6.35) 38 (0,-5,0) 11 (-7.51,7.51,7.51) 25 (-6.35,6.35,6.35) 39 (0,0,5) 12 (-7.51,7.51,-7.51) 26 (-6.35,6.35,-6.35) 40 (0,0,-5) 13 (-7.51,-7.51,7.51) 27 (-6.35,-6.35,6.35) 14 (-7.51,-7.51,-7.51) 28 (-6.35,-6.35,-6.35)

[0127] 4. Verification of the design model

[0128] 4.1 Verification of compliance with design parameter requirements

[0129] After verification, the lower limit of the energy measurement of the single-sphere neutron spectrometer is 0.006 eV, and the upper limit is 18 MeV. After repeating the calculation 100 times, the calculated result of the angular response of the single-sphere neutron spectrometer is 1.88%, which meets the design parameter requirements;

[0130] 4.2 Verification of Meeting the Requirements of the Spectrum Resolution Ability

[0131] Select 252 The Cf source is used as the reference source. The comparison of the energy spectrum parameters obtained by calculating the energy spectrum with the reference spectrum is shown in the following table.

[0132] Energy spectrum parameters Reference spectrum Simulated spectrum deconvolution result <![CDATA[Fluence-dose conversion coefficient (pSv·cm 2 )]]> 720 698 Average energy (MeV) 0.071 0.066

[0133] The deviation of the energy spectrum parameters from the reference spectrum does not exceed 10%, indicating that the ability of the single-sphere neutron spectrometer to obtain the neutron energy spectrum meets the requirements.

[0134] Example 2

[0135] This example provides a neutron spectrometer designed by adopting the design method in the above Example 1, which includes a moderator and a detector; the moderator is a spherical structure made of polyethylene; multiple detectors are arranged at depths less than or equal to 3 cm and greater than or equal to 4 cm from the surface of the moderator, and multiple detectors at the same depth are symmetrically arranged.

[0136] The neutron spectrometer of the present invention is based on setting the moderator as a sphere and arranging multiple detectors at different depths, that is, the detectors are distributed at different depths and multiple detectors are arranged at the same depth. Therefore, it can respond to neutrons in the low-energy region and the high-energy region, improve the applicable range, and realize online measurement with a single neutron spectrometer. The measurement process is simple and the applicable range is wider; moreover, by evenly distributing the detectors at the same depth, the angular response can be reduced.

[0137] In some preferred embodiments, the radius of the moderator is 15 cm; the set depths of the detectors include 2 cm, 4 cm, 7 cm, and 10 cm, thereby realizing the response in the high-energy region and the low-energy region; the specific response curve is as Figure 5 shown.

[0138] In some preferred embodiments, in order to reduce the angular response and save the number of detectors, the number of detectors arranged at the depths of 2 cm and 4 cm is greater than the number of detectors arranged at the depths of 7 cm and 10 cm.

[0139] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the present invention and the claims, and all of them belong to the protection scope of the present invention.

Claims

1. A design method of a spherical on-line neutron spectrometer, the on-line neutron spectrometer comprising a spherical moderator and a detector; characterized in that, The described design method includes the following steps: Step 1: Determine the design parameters, which at least include the energy measurement range and the angular response range; Step 2: Determine the material of the moderator; Step 3: Construct test models of multiple neutron spectrometers, where the depth of the detector settings between the test models and / or the number of detectors set at the same depth are different; Step 4: Calculate the energy response of each test model under 4π uniform incidence; Step 5: Determine the setting depth and the number of settings of the detector based on the calculation results of the energy response of each test model to obtain a design model; Step 6: Model according to the design model to obtain a simulation model, and verify whether the simulation model meets the requirements of the energy measurement range and the angular response range. If it meets the requirements, the design model is qualified. If it does not meet the requirements, the design model is unqualified, and repeat steps 3 to 6 until the simulation model meets the requirements of the energy measurement range and the angular response range.

2. The design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that, The material of the moderator is a hydrogen-rich material.

3. The design method of a spherical online neutron spectrometer according to claim 1, characterized in that, The step of calculating the energy response of each test model under 4π uniform incidence includes: Select multiple equally spaced incident angles within the 4π range at the same depth; Calculate the neutron energy response of the test model at each incident angle; Perform weighted averaging on the obtained neutron energy responses of multiple test models to obtain the energy response of the test model under 4π uniform incidence.

4. The design method of a spherical online neutron spectrometer according to claim 3, characterized in that, The weight factor for the weighted averaging is the ratio of the area of the sphere corresponding to the intersection line of the cone with the vertex at the center of the moderator sphere and the sphere where the detector is located to the area of the sphere, and the apex angle of the cone is twice the incident angle.

5. The design method of a spherical online neutron spectrometer according to claim 3, characterized in that, Neutrons at the same incident angle include multiple different energy values.

6. The design method of a spherical on-line neutron spectrometer according to claim 3, characterized in that, The interval of the incident angle is 5 - 30°.

7. The design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that The setting depth of the detector includes depths less than or equal to 3 cm and greater than or equal to 4 cm, and the depth is the radial distance from the detector to the surface of the moderator.

8. The design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that The detectors at the same depth are evenly distributed.

9. The design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that, It also includes the step of modeling according to the design model to obtain a test model and verifying whether the test model meets the neutron energy spectrum unfolding ability requirement, including: Use the parameters of the design model as input items for Monte Carlo modeling; Select a reference source, and calculate the counts of each detector in the test model at the reference source through Monte Carlo modeling; Inverse solve the neutron energy spectrum based on the counts of each detector through an energy spectrum algorithm; Calculate the degree of consistency of the energy spectrum parameters of the neutron energy spectrum and the reference spectrum. If the deviation is less than or equal to 10%, the energy spectrum unfolding ability of the test model meets the requirements.

10. A design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that, The step of verifying whether the test model meets the energy measurement range requirement includes: According to the test model, calculate the energy response function of the test model at different incident angles, and the neutron energy range corresponding to the energy response function includes the energy measurement range; For each response function curve, take the energy range interval corresponding to the response greater than 50% of the peak value of the response function curve. Take the union of the energy intervals corresponding to the responses of each curve being greater than 50% of the peak value, and use the upper and lower limits of the union as the lower and upper limits of the energy measurement of the test model; Judge whether the lower and upper limits of the energy measurement of the test model meet the requirements of the energy measurement range.

11. The design method of a spherical on-line neutron spectrometer according to claim 1, characterized in that, The steps of verifying whether the test model meets the requirements of the angular response range include: Select a reference source, calculate the counts of each detector of the test model when measuring the reference source through Monte Carlo modeling, obtain the neutron energy spectrum by inverse solution through the energy spectrum algorithm, and calculate the total neutron fluence; Randomly change the incident direction of the reference source n times within the 4π solid angle range to obtain n sets of the total neutron fluence; Calculate the average value and standard deviation of the results of n sets of the total neutron fluence, and divide the standard deviation by the average value as the calculation result of the angular response of the test model; Compare the calculation result of the angular response of the test model with the angular response range to judge whether it meets the requirements.

12. A neutron spectrometer designed by adopting the design method described in any one of the above claims 1-11, characterized in that, It includes a moderator and detectors; The moderator is a spherical structure made of polyethylene; A plurality of detectors are arranged at depths less than or equal to 3 cm and greater than or equal to 4 cm from the surface of the moderator, and the plurality of detectors at the same depth are symmetrically arranged.

13. The neutron spectrometer according to claim 13, characterized in that, The radius of the moderator is 15 cm; the set depths of the detectors include 2 cm, 4 cm, 7 cm, and 10 cm.

14. The neutron spectrometer according to claim 13, wherein The number of detectors arranged at depths of 2 cm and 4 cm is greater than the number of detectors arranged at depths of 7 cm and 10 cm.

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