A method for monitoring the concentration of Sr-90 in a radionuclide production line

Abstract

The application relates to a Sr-90 concentration monitoring method on a radionuclide production line, which is based on two same detectors A and B and a processing display unit, the two detectors A and B are symmetrically arranged on the two sides of a pipeline through which radioactive solution flows, the detector A and the detector B are in communication with the processing display unit, a light transmission hole matched with the shape and size of the window of the A detector is arranged at the corresponding position of the pipeline at the installation position of the A detector, the radioactive solution in the pipeline is detected by using the A detector, the contribution M1 of the A detector is obtained, the radioactive solution in the pipeline is detected by using the B detector, the contribution M2 of the B detector is obtained, and the moment when Sr-90 starts to be generated is determined according to M1 and M2. According to the change of the radiation dose rate value, the method disclosed in the application can judge the moment when Sr-90 is generated and the concentration change process, can exclude the interference of cesium radiation in the pipeline, and can accurately judge the moment when the Sr-90 concentration in the liquid increases.

Description

Technical Field

[0001] This invention belongs to the field of radiation monitoring, specifically relating to a method for monitoring Sr-90 concentration on a radioactive nuclide production line. Background Technology

[0002] As nuclear power reactors operate, the amount of spent radioactive fuel continuously increases. To extract radionuclides such as Sr-90 from spent fuel, a radionuclide production line needs to be constructed. On the Sr-90 production line, the feed liquid in the pipelines mainly contains calcium, strontium, small amounts of lanthanides, small amounts of barium, and small amounts of cesium. Its outflow order is cesium, calcium, strontium, barium, and lanthanum. After the feed liquid passes through an ion exchange column and is eluted, the ions are eluted sequentially from the ion exchange column.

[0003] A set of detectors needs to be installed after the ion exchange column to monitor the dose of beta and gamma radiation. Based on the change in dose rate, it is determined whether a large amount of Sr-90 appears in the feed solution in the pipeline. When no or a small amount of Sr-90 is detected, the feed solution in the pipeline flows into the waste liquid tank. When a large amount of Sr-90 is detected, the feed solution in the pipeline flows into the ion collection pipeline.

[0004] In the design of the monitoring system's detector structure, the installed detector needs to simultaneously monitor both beta and gamma radiation in the pipeline liquid. Cesium in the radioactive solution emits 662 keV gamma rays and 512 keV beta rays, while Sr-90 emits 546 keV beta rays. Throughout the entire production process, a certain amount of cesium is present. Cesium radiation within the pipeline interferes with the monitoring of Sr-90 concentration, reducing the accuracy of Sr-90 concentration monitoring in the liquid. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for monitoring Sr-90 concentration on a radioactive nuclide production line, based on... Dose rate measurement is used to monitor the Sr-90 concentration in the production of radionuclides. Based on the changes in radiation dose rate, the timing of Sr-90 generation and concentration changes in the production process can be determined. This method can eliminate interference from cesium radiation in pipelines and accurately determine the moment when the Sr-90 concentration in the liquid increases.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for monitoring Sr-90 concentration on a radioactive nuclide production line, the method being based on a Sr-90 concentration monitoring system on a radioactive nuclide production line. The system includes two identical A detectors and B detectors, and a processing and display unit. The two detectors are symmetrically arranged on both sides of a pipe through which the radioactive solution flows. Detectors A and B communicate with the processing and display unit. At the installation location of detector A, a light-transmitting hole matching the shape and size of the detector A window is opened at a corresponding position in the pipe. The method includes the following steps:

[0008] S1. Using detector A to detect the radioactive solution in the pipe, the combined effect of β and γ rays emitted from the radioactive solution on detector A is obtained. Contribution M1;

[0009] S2. Using detector B to detect the radioactive solution in the pipe, the gamma rays emitted from the radioactive solution are obtained from detector B. Contribute M2;

[0010] S3, according to detector A Contributing to the M1 and B detectors Contribution M2 determines the start time of Sr-90 generation.

[0011] Furthermore, step S3 includes the following sub-steps:

[0012] S31, the B detector Contribute M2 multiplied by the calibration factor N of the B detector for the gamma rays emitted by Cs-137. γ To obtain the gamma rays emitted by the solution being tested. Contribution

[0013] S32, using detector A Contribution M1 minus detector B Contribution M2 is used to obtain the contribution M3 of β rays to the detector;

[0014] S33. Multiply M3 by the calibration factor N for the Sr-90 β-rays of detector A. β To obtain β-ray pairs Contribution

[0015] S34, Processing display unit according to and The changes determine the starting point of Sr-90 generation.

[0016] Furthermore, in step S33, the calibration factor N for the β-rays of Sr-90 by detector A. β Take detector A at 85Calibration factor in the Kr standard radiation field.

[0017] Furthermore, in step S34, the display unit processes and displays the changes in the form of curve graphs. and The changes.

[0018] Furthermore, in step S34 when Maintaining a low dose rate with minimal variation, and The value increases significantly with the increase of Sr-90 concentration in the solution, which confirms that Sr-90 has begun to be produced.

[0019] Furthermore, detector B is positioned outside the pipe through which the radioactive solution flows.

[0020] Furthermore, detector A is surrounded by a layer of polytetrafluoroethylene material.

[0021] Furthermore, the thickness of the polytetrafluoroethylene material in front of the detection window of detector A is less than 0.5 mm.

[0022] Furthermore, detectors A and B showed consistent responses to gamma rays.

[0023] Furthermore, each of detectors A and B is provided with a sealed outer casing.

[0024] The beneficial technical effect of this invention is that it employs a monitoring system containing dual detectors to monitor β radiation on the production line. The contribution is measured, and the timing and concentration change of Sr-90 generation are determined based on the changes in radiation dose rate. Attached Figure Description

[0025] Figure 1 This is the monitoring system upon which the Sr-90 concentration monitoring method on a radionuclide production line, as shown in Embodiment 1 of the present invention, is based. Detailed Implementation

[0026] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0027] Example 1

[0028] This invention provides a method for monitoring Sr-90 concentration on a radionuclide production line, such as... Figure 1As shown, the method is based on a Sr-90 concentration monitoring system on a radioactive nuclide production line. The system includes two detectors, A and B, and a processing and display unit. The two detectors are symmetrically arranged on both sides of the pipe through which the radioactive solution flows. Detector A is used to measure the dose rate contributed by all beta rays and gamma rays emitted in the solution. In order to avoid the pipe absorbing beta rays, a light-transmitting hole matching the shape and size of the detector window is opened at the corresponding position of the pipe where detector A is installed.

[0029] Detector B has the exact same structure as detector A; both measure directional dose rate. Because the pipe through which the radioactive solution flows has a wall thickness greater than 2 mm, it can absorb all the beta rays emitted by Cs-137 and Sr-90, allowing only gamma rays to be incident on the sensitive volume of the B detector. The B detector is used to measure the dose rate of gamma rays emitted by the radioactive solution in the pipe.

[0030] The signals measured by detectors A and B are transmitted to the processing and display unit. After analysis and processing, the contribution of beta rays in the radioactive solution inside the pipe can be displayed in real time. Numerical value, gamma-ray contribution Numerical value.

[0031] The responses of detectors A and B to gamma rays are basically the same, meaning that the dose rate values ​​measured in the same gamma radiation field are basically equal.

[0032] To prevent radioactive solutions from entering the detector, detector A is surrounded by a layer of polytetrafluoroethylene (PTFE) material, with the thickness of the PTFE material in front of the detector window being less than 0.5 mm.

[0033] To prevent radioactive solutions from spilling into the environment, both detector A and detector B are enclosed in a sealed shell.

[0034] The method includes the following steps:

[0035] S1. Detector A is used to detect the radioactive solution being tested in the pipe. The combined effect of β and γ rays emitted from the radioactive solution on detector A is obtained. Contribution M1;

[0036] S2. Using detector B to detect the radioactive solution in the pipe, the gamma rays emitted from the radioactive solution are obtained from the detector B. Contribute M2;

[0037] S3, according to detector A Contributing to the M1 and B detectors Contribution M2 determines the start time of Sr-90 generation. Step S3 includes the following sub-steps:

[0038] S31. The processing and display unit multiplies M2 by the calibration factor N of the B detector for the gamma rays emitted by Cs-137. γ To accurately obtain the gamma rays emitted by the solution being tested. Contribution value

[0039] S32. The processing and display unit subtracts M2 from M1 to obtain the contribution M3 of β-rays to the detector;

[0040] S33. The processing and display unit multiplies M3 by the calibration factor N for Sr-90 β-rays of detector A. β To accurately obtain the β-ray pair Contribution

[0041] Because the β energy range emitted by Sr-90 is similar to... 85 The β energies emitted by Kr are similar; therefore, the calibration factor N for the β rays emitted by detector A from Sr-90 is... β Detector A can be taken at 85 Calibration factor in the Kr standard radiation field.

[0042] S34. The processing and display unit displays the changes in the form of graphs. and Changes; when Maintaining a low dose rate with minimal variation, and The value increases significantly with the increase of Sr-90 concentration in the solution, which confirms that Sr-90 has begun to be produced.

[0043] According to the process flow, the initial solution in the pipeline mainly contains Cs-137, which emits both beta and gamma rays. Both detectors will record radiation dose rate values; therefore, at this point, the curve will show... and The values ​​are all relatively large;

[0044] As Cs-137 in the solution decreases, calcium in the solution increases. Since calcium is not radioactive, the increase in calcium does not detect [the presence of radioactive substances]. and The values ​​will decrease significantly;

[0045] As calcium in the solution decreases, Sr-90 in the solution increases. Since Sr-90 is only β-radioactive, the detected levels are lower during the increase of Sr-90. Maintaining a low dose rate with little variation, but The value increases significantly with the increase of Sr-90 concentration in the solution. This change process can determine the generation process of Sr-90, that is, the process by which the radioactive solution flows into the collection pipe.

[0046] As can be seen from the above embodiments, the Sr-90 concentration monitoring method on a radioactive nuclide production line disclosed in this invention can eliminate the interference of cesium radiation in the pipeline, accurately determine the Sr-90 generation time and concentration change process in the production process state machine based on the change of radiation dose rate, and promptly allow the radioactive solution to flow into the ion collection pipeline.

[0047] The method described in this invention is not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solution of this invention also fall within the scope of technical innovation of this invention.

Claims

1. A method for monitoring Sr-90 concentration on a radioactive nuclide production line, the method being based on a Sr-90 concentration monitoring system on a radioactive nuclide production line, the system comprising two identical A detectors and B detectors, and a processing and display unit, the two detectors being symmetrically arranged on both sides of a pipe through which the radioactive solution flows, the A detectors and B detectors communicating with the processing and display unit, and a light-transmitting hole matching the shape and size of the A detector window being opened at a corresponding position in the pipe at the A detector installation location, the method comprising the following steps: S1. Using detector A to detect the radioactive solution in the pipe, the combined effect of β and γ rays emitted from the radioactive solution on detector A is obtained. Contribution M1; S2. Using detector B to detect the radioactive solution in the pipe, the gamma rays emitted from the radioactive solution are obtained from detector B. Contribute M2; S3, according to detector A Contributing to the M1 and B detectors Contribution M2 determines the start time of Sr-90 generation.

2. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 1, characterized in that, Step S3 includes the following sub-steps: S31, the B detector Contribute M2 multiplied by the calibration factor N of the B detector for the gamma rays emitted by Cs-137. γ To obtain the gamma rays emitted by the solution being tested. Contribution S32, using detector A Contribution M1 minus detector B Contributing M2, we obtain the contribution M3 of β rays to the detector; S33. Multiply M3 by the calibration factor N for the Sr-90 β-rays of detector A. β To obtain β-ray pairs Contribution S34, Processing display unit according to and The changes determine the starting point of Sr-90 generation.

3. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 2, characterized in that: The calibration factor N of the A detector to the β ray of Sr-90 in step S33 β Taking the calibration factor of the A detector in the Kr standard radiation field 85 Kr standard radiation field.

4. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 2, characterized in that: In step S34, the display unit processes and displays the changes in the form of curve graphs. and The changes.

5. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 2, characterized in that: In step S34 when Maintaining a low dose rate with minimal variation, and The value increases significantly with the increase of Sr-90 concentration in the solution, which confirms that Sr-90 has begun to be produced.

6. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 1, characterized in that: Detector B is positioned outside the pipe through which the radioactive solution flows.

7. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 1, characterized in that: Detector A is surrounded by a layer of polytetrafluoroethylene material.

8. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 7, characterized in that: The thickness of the polytetrafluoroethylene material in front of the detection window of detector A is less than 0.5 mm.

9. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 1, characterized in that: Detector A and Detector B respond identically to gamma rays.

10. The method for monitoring Sr-90 concentration on a radioactive nuclide production line as described in claim 1, characterized in that: Each of detectors, A and B, is equipped with a sealed outer casing.

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