CN114236591A - Dose rate measurement value-based method for adjusting size of collimation hole and distance of detector - Google Patents
Dose rate measurement value-based method for adjusting size of collimation hole and distance of detector Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000002699 waste material Substances 0.000 claims abstract description 62
- 239000010813 municipal solid waste Substances 0.000 claims abstract description 13
- 230000000694 effects Effects 0.000 claims abstract description 11
- 230000002285 radioactive effect Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 abstract description 19
- 238000009659 non-destructive testing Methods 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 239000002901 radioactive waste Substances 0.000 description 3
- 229910052732 germanium Inorganic materials 0.000 description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 2
- 238000000342 Monte Carlo simulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000000941 radioactive substance Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/167—Measuring radioactive content of objects, e.g. contamination
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/17—Circuit arrangements not adapted to a particular type of detector
- G01T1/178—Circuit arrangements not adapted to a particular type of detector for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water
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Abstract
The invention relates to a method for adjusting the size of a collimation hole and the distance of a detector based on a dose rate measuring value, which comprises the following steps: (S1) transferring the waste bin to a measuring turntable and positioning; (S2) detecting the gamma dose rate of the surface of the trash can by a gamma dose rate monitor; (S3) adjusting the size of the collimator aperture in the detecting device and the distance between the detector in the detecting device and the waste bin according to the gamma dose rate measurement result; (S4) after the adjustment is completed, the detecting device performs normal measurement on the trash can. The method is suitable for a passive gamma nondestructive detection method, prejudges the gamma dose rate level on the surface of the waste barrel in a short time, and automatically selects the optimal collimator aperture and the distance between the detector and the waste barrel by combining a Monte Carlo program simulation database on the basis, thereby avoiding the 'blockage' caused by overhigh waste activity in the barrel and creating good conditions for accurate measurement and analysis of equipment.
Description
Technical Field
The invention belongs to the radioactive substance detection technology, and particularly relates to a method for adjusting the size of a collimation hole and the distance of a detector based on a dose rate measuring value in the nondestructive detection process of a radioactive waste barrel.
Background
According to the national standard requirements, radioactive waste generated by nuclear facilities is collected, pretreated, treated and prepared to form a waste barrel in a sealed package, and the waste barrel is transported to a disposal site for disposal after being stored. The waste generation unit needs to fill the information of the total activity of the waste, the main radionuclide and the activity concentration thereof in the waste bucket file. Since the waste bin is not usually sampled and analyzed after being produced, only nondestructive testing can be used to measure the waste bin to obtain nuclide and activity information. The gamma nondestructive detection technology is the most widely used method at present, the size of a collimation hole at the front end of a detector and the distance between the detector and a waste barrel are two very important design parameters during detection, the Monte Carlo method is usually used for calculating the detection efficiency of the gamma nondestructive detection technology for the waste barrel, and the size of the collimation hole and the distance between the detector and the barrel need to be determined during modeling to complete calculation, so the two values are very important for gamma nondestructive detection equipment for the waste barrel, an efficiency scale function in equipment software needs to be adjusted after the parameters are changed, otherwise, a measurement result is wrong, and the two parameters are usually fixed. However, the apparatus with fixed parameters has a great disadvantage that the detection capability of the detector device for radioactive rays is determined, and when the radioactivity of the measured waste bin is low, the detection efficiency needs to be increased, so that the measurement time can be shortened, otherwise, sufficient counts may not be detected within the specified measurement time, and when the radioactivity of the measured waste bin is high, the detection efficiency needs to be reduced, otherwise, the counting rate of the detector is likely to exceed the detection capability of the detector, so that the detector is blocked, and the measurement result cannot be obtained.
Chinese patent application 201811444789.4 discloses a self-adaptive adjusting method for collimator aperture and detector position, which is characterized in that after a detecting device reaches a preset position, a transmission source device is opened to perform pre-transmission measurement, then the transmission source device is closed to perform pre-transmission measurement, the distance between a detector and a waste bucket in the detecting device is adjusted according to pre-transmission measurement and pre-transmission measurement parameters, and the collimator aperture is adjusted at the same time.
For the waste barrel loaded with the radioactive wastes with medium and high levels, due to the high radioactivity level of the waste barrel, the adoption of the active gamma nondestructive detection method can be greatly interfered, and only the passive gamma nondestructive detection method can be adopted. The method disclosed in the above patent application 201811444789.4 is suitable for active gamma nondestructive testing, in the current passive gamma nondestructive testing process, the size of the collimating hole at the front end of the detector and the distance between the detector and the waste barrel do not change, when the activity of the nuclide in the barrel is large, the detector may work in a high-load state, even "jam" in extreme cases, and the final nuclide activity measurement result has a large error.
Disclosure of Invention
The invention aims to provide an automatic adjusting method of the size of a collimation hole and the distance of a detector, which is suitable for a passive gamma nondestructive testing process.
The technical scheme of the invention is as follows: a method for adjusting the size of a collimation hole and the distance of a detector based on a dose rate measuring value comprises the following steps:
(S1) transferring the waste bin to a measuring turntable and positioning;
(S2) detecting the gamma dose rate of the surface of the trash can by a gamma dose rate monitor;
(S3) adjusting the size of the collimator aperture in the detecting device and the distance between the detector in the detecting device and the waste bin according to the gamma dose rate measurement result;
(S4) after the adjustment is completed, the detecting device performs normal measurement on the trash can.
Further, in the method for adjusting the size of the collimation hole and the detector distance based on the dose rate measurement value, the time for measuring the gamma dose rate on the surface of the trash can in the step (S2) is generally 5-60S (the time required for the detector to obtain stable data), a gamma dose rate measurement value X is obtained, and which interval in the monte carlo program simulation database the X is in is determined.
Further, the Monte Carlo program simulation database divides the gamma dose rate measurements into three intervals (0, X)1],(X1，X2],(X2，Xmax]Wherein X is1＜X2＜Xmax,XmaxThe upper limit value of the gamma dosage rate on the surface of the waste bucket can be detected by the device.
Further, in the method for adjusting the size of the collimation hole and the distance between the detector and the waste bin based on the dose rate measurement value as described above, in step (S3), the sizes of the apertures of the collimation hole and the distances between the corresponding detectors and the waste bin are set, and the sizes of the collimation hole and the distances between the detectors and the waste bin are adjusted according to the specific interval position in the monte carlo program simulation database where the gamma dose rate measurement value X is located.
Further, in the step (S3), three collimation hole aperture sizes D are set1＜D2＜D3And the distance L between the three detectors and the waste bin1＜L2＜L3(ii) a When the gamma dose rate measurement X is at (0, X)1]In the interval, the aperture of the collimating hole is adjusted to D3While the distance between the detector and the waste bin is adjusted to L1(ii) a When the dose rate measurement X is at (X)1，X2]In the interval, the aperture of the collimating hole is adjusted to D2While the distance between the detector and the waste bin is adjusted to L2(ii) a When the dose rate measurement X is at (X)2，Xmax]In the interval, the aperture of the collimating hole is adjusted to D1While the distance between the detector and the waste bin is adjusted to L3。
Further, the method for adjusting the collimation aperture size and the detector distance based on the dose rate measurement value as described above, in step (S4), in step (S4), 600S and 1800S (the shortest distance for the detector to obtain effective count) are performedTime) is normally measured, the corresponding Monte Carlo program of the state is called to simulate the efficiency scale function Eff (D) in the databasen，Ln) And calculating the activity of the radioactive nuclide of the waste in the waste bucket.
The invention has the following beneficial effects: the invention provides an automatic adjusting method of a collimation hole size and a detector distance based on a dose rate measuring value, which is suitable for a passive gamma nondestructive detection method, and is used for prejudging the gamma dose rate level on the surface of a waste barrel in a short time.
Drawings
Fig. 1 is a flowchart of a method for adjusting the size of a collimation hole and the detector distance based on a dose rate measurement value according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the present invention provides an automatic adjusting method of collimation hole size and detector distance suitable for passive gamma nondestructive testing process, comprising the following steps:
(S1) the trash can is transferred to the measuring turntable by the transfer means and is precisely positioned, at which time the measurement can be started;
(S2) detecting the gamma dose rate on the surface of the waste barrel through a gamma dose rate monitor;
(S3) according to the gamma dose rate measurement result, adjusting the aperture size of a collimator in a detection device, and simultaneously adjusting the distance between a detector and a waste barrel, wherein the detection device is internally provided with the collimator and a high-purity germanium detector;
(S4) after the adjustment is completed, the detecting device performs normal measurement on the trash can.
The method can be applied to a passive gamma nondestructive testing process, firstly, the activity of the waste in the waste barrel is judged by adopting a mode of measuring the gamma dose rate on the surface of the waste barrel, then, a Monte Carlo program simulation database is used for automatically adjusting the aperture of the collimator and the distance between the detector and the waste barrel to the optimal position, and then, normal measurement is carried out. The purpose is to make the detector work under normal load state, avoid causing "stifled because the rubbish activity is too high in the bucket. The Monte Carlo program simulation database is a database which adopts Monte Carlo program simulation and has different collimation hole sizes and detection efficiency of detector distance.
In a specific embodiment, in step (S2), the gamma dose rate on the surface of the trash can is measured for 5-60S, and a gamma dose rate measurement value X is obtained, and how to adjust the size of the collimation hole and the detector distance is determined by determining which interval of the monte carlo program simulation database X is located.
Specifically, the Monte Carlo program simulation database may divide the dose rate measurements into the following three intervals (0, X)1],(X1，X2],(X2，Xmax]Wherein X is1＜X2＜Xmax,XmaxThe upper limit value of the gamma dosage rate on the surface of the waste bucket can be detected by the device.
Accordingly, in step (S3), three collimation hole aperture sizes D are set1＜D2＜D3And the corresponding distances L between the three detectors and the waste bin1＜L2＜L3。
When the gamma dose rate measurement X is at (0, X)1]In the interval, the aperture of the collimating hole is adjusted to D3While the distance between the detector and the waste bin is adjusted to L1(ii) a When the dose rate measurement X is at (X)1，X2]In the interval, the aperture of the collimating hole is adjusted to D2While the distance between the detector and the waste bin is adjusted to L2(ii) a When the dose rate measurement X is at (X)2，Xmax]In the interval, the aperture of the collimating hole is adjusted to D1While the distance between the detector and the waste bin is adjusted to L3。
Further, in step (S4), after the normal measurement of 600 + 1800S is completed, the efficiency scale function Eff (D) in the database corresponding to this state is calledn，Ln) And calculating the activity of the radioactive nuclide of the waste in the waste bucket.
The invention uses the gamma dose rate measured value on the surface of the waste barrel to automatically adjust the size of the collimation hole and the distance between the detector and the waste barrel so as to achieve the purpose of adjusting the detection efficiency, and simultaneously selects the corresponding efficiency scale function to ensure the accuracy of the measurement, thereby providing an optimized solution for gamma nondestructive testing and greatly improving the applicable measurement range of the equipment.
With D1、D2、D3Respectively 1cm, 3cm, 6cm, L1、L2、L3Respectively of 0.1m, 1m and 3m, the detector is a high-purity germanium crystal with the diameter of 80mm and the height of 31mm, and the measured average density is 0.3g/cm3The calculated X is taken as an example of gamma rays emitted in the waste bin with an energy of 1.33MeV1、X2、XmaxRespectively at 0.1mGy/h, 4.3mGy/h, 78Gy/h, Eff (6cm, 0.1m), Eff (3cm, 1m), Eff (1cm, 3m) respectively at 1.03E-5, 4.70E-7, 4.58E-12.
When the gamma dose rate measurement value X is in a (0, 0.1 mGy/h) interval, the aperture of the collimation hole is adjusted to be 6cm, the distance between the detector and the waste barrel is adjusted to be 0.1m, and the numerical value of the efficiency scale function called in the calculation is 1.03E-5, when the dose rate measurement value X is in a (0.1mGy/h, 4.3 mGy/h) interval, the aperture of the collimation hole is adjusted to be 3cm, the distance between the detector and the waste barrel is adjusted to be 1m, and the numerical value of the efficiency scale function called in the calculation is 4.70E-7, when the dose rate measurement value X is in a (4.3mGy/h, 78 Gy/h) interval, the aperture of the collimation hole is adjusted to be 1cm, the distance between the detector and the waste barrel is adjusted to be 3m, and the numerical value of the efficiency scale function called in the calculation is 4.58E-12.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (6)
1. A method for adjusting the size of a collimation hole and the distance of a detector based on a dose rate measuring value comprises the following steps:
(S1) transferring the waste bin to a measuring turntable and positioning;
(S2) detecting the gamma dose rate of the surface of the trash can by a gamma dose rate monitor;
(S3) adjusting the size of the collimator aperture in the detecting device and the distance between the detector in the detecting device and the waste bin according to the gamma dose rate measurement result;
(S4) after the adjustment is completed, the detecting device performs normal measurement on the trash can.
2. The dose rate measurement based collimation aperture size and detector distance adjustment method of claim 1, wherein the time for measuring the gamma dose rate on the surface of the trash can in step (S2) can be set to be generally 5-60S, obtaining the gamma dose rate measurement value X, and determining which interval X is in the monte carlo program simulation database.
3. The dose rate value based collimation aperture size and detector distance adjustment method of claim 2, wherein the monte carlo program simulation database divides the gamma dose rate measurement into three intervals (0,X1],(X1，X2],(X2，Xmax]wherein X is1＜X2＜Xmax,XmaxThe upper limit value of the gamma dosage rate on the surface of the waste bucket can be detected by the device.
4. The dose rate measurement based collimation aperture size and detector distance adjustment method of claim 2, wherein in step (S3), a plurality of collimation aperture sizes and corresponding distances between a plurality of detectors and the trash can are set, and the collimation aperture size and the detector distance are adjusted according to the specific interval position in the monte carlo program simulation database where the gamma dose rate measurement X is located.
5. Dose rate value based collimation aperture size and detector distance adjustment method as claimed in claim 3, wherein in step (S3), three collimation aperture sizes D are set1＜D2＜D3And the distance L between the three detectors and the waste bin1＜L2＜L3(ii) a When the gamma dose rate measurement X is at (0, X)1]In the interval, the aperture of the collimating hole is adjusted to D3While the distance between the detector and the waste bin is adjusted to L1(ii) a When the dose rate measurement X is at (X)1，X2]In the interval, the aperture of the collimating hole is adjusted to D2While the distance between the detector and the waste bin is adjusted to L2(ii) a When the dose rate measurement X is at (X)2，Xmax]In the interval, the aperture of the collimating hole is adjusted to D1While the distance between the detector and the waste bin is adjusted to L3。
6. The method as claimed in claim 1, wherein in step (S4), after the 600-1800S normal measurement is completed, the method calls the corresponding Monte Carlo program to simulate the efficiency scale function Eff (D) in the databasen，Ln) And calculating the activity of the radioactive nuclide of the waste in the waste bucket.
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