Solid-state radioactive source term measurement method

Abstract

This invention provides a method for measuring solid-state radioactive source terms. By using a gamma-ray detector with a narrow window to scan the inside of a pipeline in multiple directions, the distribution data of nuclide energy within the pipeline is obtained. Comparative analysis is then performed to determine the content of solid-state source terms in the pipeline. This method utilizes the difference in uniformity between gaseous and solid-state source terms within the pipeline. Scanning is performed axially, vertically along the same cross-section, and circumferentially along the same cross-section, simultaneously acquiring the contributions of both gaseous and solid-state source terms. Comparative analysis yields the contribution level of the solid-state source terms, which in turn determines the deposition level of graphite dust and evaluates the degree of damage to fuel elements. This method enables online measurement of deposited source terms in high-temperature gas-cooled reactor loop systems, significantly reducing the dose levels associated with frequent on-site source term measurements.

Description

Technical Field

[0001] The invention belongs to the field of radioactive material measurement, and in particular relates to a solid-state radioactive source term measurement method. Background Art

[0002] The pebble bed high temperature gas-cooled reactor uses spherical fuel elements. When the reactor is operating normally, the spherical fuel elements move slowly from top to bottom inside the core, and enter the fuel loading and unloading system after reaching the pressure vessel unloading pipe for fuel circulation and loading and unloading outside the core. During the circulation and loading and unloading process of the fuel balls, graphite dust and debris will be generated between the balls, between the balls and the components inside the core, between the balls and the inner wall of the metal pipe, and between the balls and the rotating parts of the conveying equipment. Some dust and debris will be deposited or adhered to the inner wall of the fuel loading and unloading system loop pipe. In order to ensure the stable operation of the fuel loading and unloading system and obtain the source term level inside the system, it is necessary to evaluate the dust and debris deposition.

[0003] In order not to affect the normal operation of the system, it is necessary to obtain the gamma radioactive information generated in the tube and released by penetrating the tube wall from the outside to achieve non-destructive testing. The gamma spectrometer can distinguish the energy of the gamma rays and the intensity level of the energy, so as to distinguish which nuclide the rays are produced by and the activity level of the nuclide, that is, to analyze the main radioactive nuclides in the tube. However, since the tube is full of coolant, a large amount of fission and activation gas will be generated during the operation of the reactor, and it will also circulate in the tube with the coolant, and the radioactive nuclides contained in these gases and the nuclides contained in the above-mentioned detached and deposited solids have many overlapping parts. This results in that although the measurement results contain nuclide information, it is impossible to distinguish whether they come from airborne source terms or solid deposition source terms, and thus it is impossible to evaluate the deposition level of graphite dust inside the pipeline.

[0004] Related literature discloses an online measurement system for the activity of radioactive nuclides γ, which can perform measurements without contacting or destroying the pressure boundary of the loop system. However, this system can only provide the nuclides of the liquid medium in the loop, and cannot meet the requirements of measuring gaseous source terms and solid source terms separately.

[0005] The relevant literature also discloses an online nuclide analysis detector for the primary water loop of a pressurized water reactor. Compared with the above-mentioned "Online Measurement System for the Activity of Radioactive Nuclides γ", an anti-Compton component is added, which further suppresses the Compton effect produced by higher energy nuclides, reduces the interference of the environmental background, improves the nuclide resolution capability, and improves the detector efficiency of the measurement pipeline. However, the above measures still cannot distinguish whether the measured nuclide energy comes from gas or solid, and thus cannot meet the needs of high-temperature gas-cooled reactors to distinguish between gaseous source terms and solid source terms, and then evaluate the degree of graphite ball damage. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0007] To this end, an embodiment of the present invention provides a solid-state radioactive source term measurement method.

[0008] The solid-state radioactive source term measurement method of the embodiment of the present invention uses a gamma-ray detector with a narrow window to scan the pipeline in multiple directions to obtain the distribution data of the nuclide energy in the pipeline, and obtains the content of the solid-state source term in the pipeline through comparative analysis. In some embodiments, the gamma-ray detector has a narrow window.

[0009] In some embodiments, the solid-state radioactive source term measurement method can obtain the distribution data of the nuclide energy in the pipeline by the following methods;

[0010] Using a gamma-ray detector to scan back and forth in the axial direction of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the axial direction of the pipeline;

[0011] On any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to scan back and forth in the up and down directions to obtain distribution data of nucleus energy in the pipeline in the up and down directions.

[0012] At any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to rotate and scan around the circumference of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the circumferential direction of the pipeline.

[0013] The solid-state radioactive source term measurement method of the embodiment of the present invention utilizes the difference between uniform and uneven distribution of gaseous source terms and solid source terms in the pipe to scan the pipe in the axial direction of the pipe, in the up-down direction on the same cross section, and in the circumferential direction on the same cross section, and simultaneously obtains the contribution of gaseous source terms and solid source terms, and obtains the contribution level of the solid source terms through comparative analysis, and then analyzes and obtains the deposition level of graphite dust and evaluates the degree of damage to the fuel element. The solid-state radioactive source term measurement method of the embodiment of the present invention can realize the online measurement of the deposition source terms of the high-temperature gas-cooled reactor loop-related system, and can greatly reduce the dose level of the staff who frequently enter the site to carry out source term measurement work. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of measurement in the axial direction of a pipeline in an embodiment of the present invention;

[0015] Figure 2 It is a schematic diagram of measurement in the cross-sectional direction of a pipeline in an embodiment of the present invention.

[0016] Figure numbers: 1. Pipeline; 2. Solid source term; 3. Gaseous source term; 4. Gamma-ray detector. DETAILED DESCRIPTION

[0017] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0018] Reference below Figure 1-2 The solid-state radioactive source term measurement method proposed in an embodiment of the present invention is described in detail.

[0019] The solid-state radioactive source term measurement method of the embodiment of the present invention uses a gamma-ray detector with a narrow window to scan the pipeline in multiple directions to obtain the distribution data of the nuclide energy in the pipeline, and obtains the content of the solid source term in the pipeline through comparative analysis.

[0020] Since the gaseous source term can be treated as uniformly distributed in space, while the solid source term is non-uniform, the contribution level of the solid source term can be obtained by comparing and analyzing the results measured by the gamma-ray detector, and then the nuclide level of the solid source term can be obtained.

[0021] In some extreme cases, the solid source term in the pipeline is also uniform. If the single measurement result is the sum of gaseous and solid contributions, it is impossible to determine the proportion of the two contributions. This situation can be distinguished by time, that is, multiple measurements are performed within a reasonable time period.

[0022] The concentration of the gas source term can be considered uniform in a short period of time, but the uniform solid source term will change due to the friction caused by the internal movement of the graphite fuel ball or the purge effect of the airflow. Since the previous uniform state will be broken, the position with the lowest activity level is the position where the solid source term contributes the least. The contribution level of the gas source term is obtained based on this result, and the contribution level of the gas source term is subtracted from the sum of the measured nuclide energies as the deduction base to obtain the nuclide energy of the solid source term.

[0023] In some embodiments, the distribution data of the nuclide energy in the pipeline can be obtained by the following method:

[0024] Using a gamma-ray detector to scan back and forth in the axial direction of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the axial direction of the pipeline;

[0025] On any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to scan back and forth in the up and down directions to obtain distribution data of nucleus energy in the pipeline in the up and down directions.

[0026] At any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to rotate and scan around the circumference of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the circumferential direction of the pipeline.

[0027] The solid-state radioactive source term measurement method of the embodiment of the present invention utilizes the difference between uniform and uneven distribution of gaseous source terms and solid source terms in the pipe to scan the pipe in the axial direction of the pipe, in the up-down direction on the same cross section, and in the circumferential direction on the same cross section, and simultaneously obtains the contribution of gaseous source terms and solid source terms, and obtains the contribution level of the solid source terms through comparative analysis, and then analyzes and obtains the deposition level of graphite dust and evaluates the degree of damage to the fuel element. The solid-state radioactive source term measurement method of the embodiment of the present invention can realize the online measurement of the deposition source terms of the high-temperature gas-cooled reactor loop-related system, and can greatly reduce the dose level of the staff who frequently enter the site to carry out source term measurement work.

[0028] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0032] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0033] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A solid-state radioactive source term measurement method, characterized in that: The pipeline is scanned by using a gamma-ray detector to obtain the distribution data of the nuclide energy in the pipeline, and the content of the solid source term in the pipeline is obtained through comparative analysis; The distribution data of nuclide energy in the pipeline is obtained by the following methods; Using a gamma-ray detector to scan back and forth in the axial direction of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the axial direction of the pipeline; On any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to reciprocate and scan in the up-down direction to obtain distribution data of the nucleus energy in the pipeline in the up-down direction; At any cross section perpendicular to the axial direction of the pipeline, a gamma-ray detector is used to rotate and scan around the circumference of the pipeline to obtain distribution data of the nuclide energy in the pipeline in the circumferential direction of the pipeline; By utilizing the difference between uniform and uneven distribution of gaseous source terms and solid source terms in the pipe, the pipe is scanned in the axial direction, in the up and down directions on the same section, and in the circumferential direction on the same section. The contributions of the gaseous source terms and solid source terms are obtained at the same time, and the contribution level of the solid source term is obtained through comparative analysis.

2. A solid-state radioactive source term measurement method according to claim 1, characterized in that: The gamma ray detector has a narrow window.

3. A solid-state radioactive source term measurement method according to claim 1, characterized in that: The pipeline is scanned in multiple directions by using a gamma-ray detector.

Images