TWI661212B - Calibration and measurement method and system for piping radioactivity contamination - Google Patents

Abstract

The invention provides a method and system for calibrating and measuring radioactive contamination of a pipeline, which uses a calibration tube and a standard radio source to calculate the response efficiency of a radiation detector in advance. After that, the radiation detection rate was measured for the same geometric shape of the pipeline to be tested with a radiation detector. Finally, according to the ratio of the radiation counting rate and the reaction efficiency, the specific radioactivity of the pipeline to be tested can be calculated. In this way, the present invention can directly reflect the radioactive contamination inside the pipeline, so that the reaction result has higher accuracy and has overall representativeness.

Description

Method and system for calibrating and measuring radioactive pollution in pipelines

The invention relates to a method and system for calibrating and measuring radioactive contamination of a pipeline, in particular to a method for pre-calibrating the response efficiency of a radiation detector by using a standard radiation source, and thereafter using a self-propelled wall-climbing robot to carry the radiation detector. A method and system for calibrating and measuring radioactive contamination in a pipeline by directly entering the inside of the pipeline to directly measure the radioactivity in the pipeline.

Numerous pipes are distributed on the ceiling, walls and floors of nuclear power plants, such as waste liquid drain pipes, water supply pump pipes, reactor cavity drain pipes, safety injection pump outlet pipes, valve chamber drainage channels, and pump pool areas of fuel pools, etc. .

Affected by radioactive materials, there will be radioactive contamination inside the pipe fittings. Based on when the radioactive contamination reaches the level that needs to be decontaminated or eliminated, pipe replacement work is required. Therefore, the level of radioactive contamination inside the individual fittings will be measured during the maintenance of the nuclear power plant or before decommissioning.

There are various methods for the calibration and measurement of radioactive contamination of pipelines, such as smear sampling, gamma-spectrum analysis, scraping sampling with radiochemical analysis, and total acidity of sections. Etching (total acid etch) and the like.

However, the sampling object of the traditional measurement method is only part of the pipeline, so the measurement results are not representative of the whole. Although the gamma spectroscopy method can measure the radioactivity from the outside of the pipeline, due to the different shapes of various pipelines, it is difficult to correct the measurement results and it is impossible to measure the correct radioactivity.

Therefore, in order to overcome the shortcomings of the prior art, the present invention proposes a method and system for calibrating and measuring radioactive contamination in pipelines. First, the response efficiency of the radiation detector is calculated using a calibration tube and a standard radio source, and then a carrier The radiation detector is driven to move in the tube to be tested, so as to actually measure the specific radioactivity of the inner wall of the tube to be tested.

According to an embodiment of the present invention, a method for calibrating and measuring radioactive contamination of a pipeline is provided, which is used to measure the specific activity of the radioactivity inside the pipe to be measured. The method for calibrating and measuring radioactive contamination of a pipeline includes the following steps. A calibration tube is provided, and the inner wall of the calibration tube has the same diameter as the inner wall of the tube to be measured. Provide a standard radioactive source, the standard radioactive source has the standard radiation activity value of the nucleus. The laying of a standard shot originates from the inner wall of the calibration tube. Provide a radiation detector and a vehicle, and the vehicle is connected to the radiation detector. Place the radiation detector and the carrier in the calibration tube. Operate the radiation detector to measure the standard radiation activity value of the radiation nuclei, and measure the corrected count rate of this standard radiation activity value. The ratio of the corrected count rate to the standard radiation activity value is used to calculate the response efficiency of the radiation detector. Place the radiation detector and the carrier in the tube to be tested. Operate the vehicle to drive the radiation detector to move inside the tube under test. Operate the radiation detector to measure one of the radiation count rates in the tube under test. The ratio of the radiation counting rate to the reaction efficiency is used to calculate the specific activity of the tube to be measured.

In this embodiment, the vehicle is used to drive the radiation detector, which can be directly moved inside the pipeline to be measured, thereby measuring the radioactive specific activity on a large scale. Compared with the conventional measurement method of local sampling measurement or external correction after external measurement of the pipeline, the measurement results of this embodiment are not only more representative, but also because this embodiment is directly Internal measurement does not need to correct the measurement results, so it has higher accuracy.

In addition, in this embodiment, the measurement operation is pre-calibrated with a standard radio source. Since the standard radiation activity value radiated by the standard radio source is known, the ratio of the measured correction count rate to the aforementioned standard radiation activity value is known. The accurate response efficiency of the radiation detector can be obtained, so that the subsequent measurement results have reliability.

In one embodiment, the aforementioned standard radiation source may be a radiation source such as cobalt-60, cesium-137, rubidium-152, or rubidium-241.

The foregoing method for calibrating and measuring radioactive contamination of pipelines may further include the following steps. Provide lighting unit and camera unit. The lighting unit and the camera unit are installed at the front end of the vehicle. The lighting unit is operated to illuminate the inner wall of the tube to be tested. Operate the camera unit to take an image of the inner wall of the tube under test. In this way, the present embodiment can simultaneously capture the image of the inside of the pipeline at the same time as the calibration and measurement of the radioactive pollution of the pipeline, as a reference basis for other maintenance work.

The aforementioned radiation detector may be cylindrical or disc-shaped. For example, in order to obtain a larger range of average measurement data, the use of a columnar radiation detector can reflect a longer range of radioactive pollution sources in the pipeline in the same unit time, thereby further increasing the overall representativeness of the measurement results. In addition, when the pipeline is bent at different angles, the disc-shaped radiation detector can smoothly pass through these bends with the carrier, and it will not be affected by geometric restrictions and cannot perform the reaction operation there.

In one embodiment, the method for calibrating and measuring radioactive contamination of the pipeline may further include the following steps. A plurality of casters are provided, and the aforementioned casters are mounted on a radiation detector. Adjust the position of each caster, make each caster abut against the inner wall of the tube to be tested or the calibration tube, and position the radiation detector at the center of the section of the tube to be tested or the calibration tube. Therefore, since the radiation detector is located at the geometric center position of the pipeline, the measurement results of the correction count rate and the radiation count rate are average values of the pipeline cross section, which has the overall representative significance.

According to another embodiment of the present invention, a calibration and measurement system for radioactive contamination of a pipeline is provided to measure the specific activity of the radioactivity inside the tube to be measured. The calibration and measurement system for radioactive contamination of a pipeline includes a calibration tube, a standard radioactive source, Radiation detectors, vehicles and processing units. The caliber of the inner wall of the calibration tube is the same as the inner wall of the tube to be measured. The standard radiation source is laid on the inner wall of the calibration tube, and the standard radiation source has the standard radiation activity value of the radiation nuclei. The radiation detector has a reaction efficiency when responding to radiation, and the radiation detector is used to measure the standard radiation activity value of the radiation nuclei to measure the corrected count rate, or to measure the radiation count rate in the tube to be measured. The carrier is connected to the radiation detector, and the carrier is for moving on the inner wall of the calibration tube or the tube under test. The processing unit calculates the reaction efficiency according to the ratio of the corrected count rate and the standard radiation activity value, and calculates the specific activity of the radioactivity according to the ratio of the radiation count rate and the reaction efficiency.

By means of the above-mentioned embodiments, the calibration and measurement system for radioactive contamination of pipelines can be applied to pipelines in nuclear power plants before maintenance or elimination of pollution reactions. Compared with the existing radioactive contamination reaction method, this embodiment has the advantages of easier operation and reduced error. In addition, since the radiation detector can move a long distance in the pipeline to be measured, the measurement results are representative of the whole, which can avoid the problem of miscalculating the degree of radiation pollution of the pipeline due to only partial measurement.

In one embodiment, the aforementioned standard radiation source may be a radiation source such as cobalt-60, cesium-137, rubidium-152, or rubidium-241.

In one embodiment, the calibration and measurement system for radioactive contamination of a pipeline may additionally include a lighting unit and a camera unit. The lighting unit is arranged at the front end of the carrier and is used to illuminate the inner wall of the tube to be tested. The camera unit is arranged at the front end of the carrier and is used to capture the image of the inner wall of the tube to be measured.

The aforementioned radiation detector may be cylindrical or disc-shaped.

The aforementioned calibration and measurement system for radioactive contamination of pipelines may further include a plurality of casters, which are arranged on the radiation detector and abut against the inner wall of the tube or calibration tube to be measured, so that the radiation detector is located on the tube or calibration The center of the section of the tube.

The description of the further embodiment of the calibration and measurement system for radioactive contamination of pipelines in this embodiment and the effects thereof are as described in the previous embodiment of the method for calibration and measurement of radioactive contamination of pipelines, so they will not be repeated here.

In order to fully understand the purpose, features and effects of the present invention, the following specific embodiments are used in conjunction with the accompanying drawings to make a detailed description of the present invention, which will be described later:

The method 100 for calibrating and measuring radioactive contamination of a pipeline is used to measure the specific activity of a radioactive substance inside the tube T to be measured. Please refer to FIGS. 1 and 2. A method 100 for calibrating and measuring radioactive contamination of a pipeline includes the following steps. Step 101 is to provide a calibration tube 300, and the inner wall of the calibration tube 300 has the same diameter as the inner wall of the tube T to be measured. Referring to FIG. 3, step 102 is to provide a standard radioactive source 400 having a standard radioactivity value of a radionuclide (eg, different nuclear species such as alpha, beta, and gamma). The standard radiation source 400 can be made into different sizes according to measurement needs, and the standard radiation activity value of each standard radiation source 400 can be measured in advance using an instrument. The standard radiation activity value described here is established after measuring the radiation activity value in the calibration tube 300 and then tracing the national standard radiation activity standard based on this value. The nuclear species contained in the standard radioactive source 400 may be cobalt-60, cesium-137, rubidium-152, or rubidium-241, but may also be other radioactive species. The manufacturing method of the standard radiation source 400 and the measurement method of the standard radiation activity are background knowledge of those skilled in the art, so they are not described in detail here.

Continuing to refer to FIGS. 4A to 6, step 103 is laying a standard radiation source 400 on the inner wall of the calibration tube 300. In this embodiment, the standard radiation source 400 is a rollable sheet, so as to automatically adapt to pipes of different calibers. Step 104 is to provide a radiation detector 500 and a carrier 600, and the carrier 600 is connected to the radiation detector 500. As shown in FIG. 4A and FIG. 4B, the surface of the radiation detector 500 is provided with one or more detection windows 510 for receiving radiation from the environment in the measurement tube. The specifications of the radiation detector 500 may be changed according to measurement needs. For example, the radiation detector 500 illustrated in FIG. 4A is cylindrical and has a plurality of detection windows 510 on the surface, which can perform fast and wide-area measurement in a long straight pipeline. As shown in FIG. 4B, the disc-shaped radiation detector 500 can smoothly pass through the curved part of the pipeline, and is suitable for being applied to an irregularly shaped pipeline. However, the radiation detector 500 in FIG. 4A and FIG. 4B is only used to describe the embodiment, and its actual aspect is not used to limit the present invention.

Step 105 is placing the radiation detector 500 and the carrier 600 in the calibration tube 300. Step 106 is to operate the radiation detector 500 to measure the standard radiation activity value (becquerel per cm ² ) of the radiation nuclei of the standard radiation source 400, and measure the corrected count rate of the standard radiation activity value. Step 107 is to calculate the response efficiency of the radiation detector 500 by using the ratio of the corrected count rate (count per second, cps) to the standard radiation activity value.

In detail, the correction tube 300 has the same geometric shape as the tube T to be tested, so the measurement environment in the tube T to be tested can be simulated. Under the same measurement conditions (geometry), the radiation detector 500 has the same response efficiency when measuring the radiation source. Therefore, in step 106, the correction count rate measured by the radiation detector 500 in the calibration tube 300 is the same as The ratio of the known standard radiation activity values (that is, the reaction efficiency) will also be consistent with the test tube T under the same conditions. Therefore, when the reaction efficiency of the radiation detector 500 in the calibration tube 300 is known, the radiation detector 500 can be applied to the test tube T of the same shape.

In this embodiment, the reaction efficiency is defined as follows.

Here, as shown in FIG. 4A and FIG. 4B, since the radiation detector 500 measures the radioactivity of the environment in the tube through the detection window 510 on its surface, the radiation detector 500 according to different specifications, Its response efficiency will also vary depending on the form of the detection window 510.

Please continue to refer to FIG. 7. Step 108 is to place the radiation detector 500 and the carrier 600 in the tube T to be tested. Step 109 is to operate the carrier 600 to drive the radiation detector 500 within the tube T to be measured. Step 110 is to operate the radiation detector 500 to measure a radiation count rate in the tube T to be measured. Step 111 is to use the ratio of the radiation counting rate and the reaction efficiency to calculate the specific radioactivity of the tube T to be tested.

As described above, on the premise that the response efficiency of the radiation detector 500 is known, the radiation detector 500 can be used to test the radiation count rate of the tube T to be tested. It should be noted that the radiation count rate is the detection result of the radiation detector 500, but the result will be affected by the response efficiency of the radiation detector 500, so the radiation count rate is not equal to the actual specific activity of radioactivity.

The specific activity of the test tube T is defined as follows.

Summarizing this embodiment, the method 100 for calibrating and measuring radioactive contamination of a pipeline is to pre-calibrate the response efficiency of the radiation detector 500 using a calibration tube 300 with the same geometric shape as the target to be measured, and then perform calibration After the reaction efficiency is adjusted to the actual measured radiological count rate, the actual radioactive specific activity can be estimated.

The following table shows the actual measurement results of the column-shaped and disc-shaped radiation detector 500 in this embodiment, and the comparison between the measurement results and the standard radiation value of the tube T to be measured. Radiation Detector (Columnar) Standard value (Bq) Measured value (Bq) difference(%) Cesium-137 153972 184711 20 Cobalt-60 160064 155670 -3 Radiation Detector (Disc) Standard value (Bq) Measured value (Bq) difference(%) Cesium-137 153972 212889 38 Cobalt-60 160064 214500 34

As can be seen from the table above, compared with the existing measurement methods, this embodiment has a higher accuracy rate, and because the radiation detector 500 is actually measured in the pipeline, the measurement results are more representative and can effectively avoid local Problems with measurement errors.

Please refer to FIG. 4A, FIG. 4B, FIG. 6 and FIG. 7 together. In order to ensure that the radiation detector 500 keeps stable running in the tube T or the calibration tube 300, a plurality of casters 520 may be additionally provided in this embodiment, and Mounted on radiation detector 500. By adjusting the position of each caster 520, the caster 520 can be pressed against the inner wall of the tube T to be measured or the calibration tube 300. In a preferred embodiment, the radiation detector 500 is located at the center of the section of the tube T or the calibration tube 300 to be measured, so as to obtain a more accurate calibration count rate and radiation count rate.

In other embodiments, the method 100 for calibrating and measuring radioactive contamination of a pipeline may further provide an illumination unit 610 and a camera unit 620. The lighting unit 610 and the camera unit 620 are both disposed at the front end of the carrier 600. The lighting unit 610 can be operated to illuminate the inner wall of the tube T to be tested, and the camera unit 620 is used to capture an image of the inner wall of the tube T to be tested. Therefore, in this embodiment, the inner wall of the tube T to be measured can be observed while measuring the specific activity of the radioactivity, as a reference for other maintenance work.

Please refer to FIG. 8 with reference to FIGS. 1 to 7. Another embodiment of the present invention is a calibration and measurement system 200 for radioactive contamination of pipelines, which is used to measure the specific activity of a radioactive substance inside the tube T to be measured. The pipeline radioactive pollution correction and measurement system 200 includes a calibration tube 300, a standard radiation source 400, a radiation detector 500, a carrier 600, and a processing unit 700. The caliber of the inner wall of the calibration tube 300 is the same as the inner wall of the tube T to be measured. The standard radiation source 400 is laid on the inner wall of the calibration tube 300, and the standard radiation source 400 has a standard radiation activity value of a radiation nucleus. The radiation detector 500 has a response efficiency when responding to radiation, and the radiation detector 500 is provided for measuring a standard radiation activity value of a radiation nucleus, thereby measuring a corrected count rate, or measuring a radiation count rate in the tube T to be measured. The carrier 600 is connected to the radiation detector 500, and the carrier 600 is for moving on the inner wall of the calibration tube 300 or the tube T to be measured. The processing unit 700 calculates the reaction efficiency according to the ratio of the corrected count rate and the standard radiation activity value, and calculates the specific activity of the radioactivity according to the ratio of the radiation count rate and the reaction efficiency.

The details of the calibration reaction efficiency and the calculation of the counting rate in this embodiment are as described in the aforementioned method 100 for the calibration and measurement of radioactive contamination of pipelines, so the description will not be repeated here.

In addition to receiving the measurement data of the radiation detector 500 and calculating the specific activity of the radioactivity based on it, the processing unit 700 can also be used as a controller of the radioactive pollution correction and measurement system 200 of the pipeline. For example, the processing unit 700 may control the vehicle 600 to move through a cable or a wireless network, turn on the lighting unit 610 and the camera unit 620, or adjust the positions of the casters 520 to adapt to the change in the diameter of the pipeline.

It is worth mentioning that on the premise that the geometric shape information of the tube T to be tested is known, the response efficiency of the radiation detector 500 can be pre-calibrated in advance for use in field measurement. Thereby, this embodiment can realize a highly mobile radioactive contamination reaction operation, and can immediately know the reaction result.

In an embodiment, the aforementioned standard radiation source 400 may be a radiation source such as cobalt-60, cesium-137, rubidium-152, or rubidium-241. The aforementioned calibration and measurement system for radioactive contamination of pipelines 200 may additionally include a lighting unit 610 and a camera unit 620. The lighting unit 610 is disposed at the front end of the carrier 600 and is used to illuminate the inner wall of the tube T to be measured. The camera unit 620 is disposed at the front end of the carrier 600 and is used to capture an image of the inner wall of the tube T to be measured. The aforementioned radiation detector 500 may be cylindrical or disc-shaped. The aforementioned pipeline radioactive pollution correction and measurement system 200 may further include a plurality of casters 520, which are provided on the radiation detector 500 and abut against the inner wall of the tube T or the calibration tube 300 to make the radiation detector 500 is located at the center of the section of the tube T to be tested or the calibration tube 300.

The implementation details and effects of the further examples of this embodiment are similar to those of the method 100 for correcting and measuring radioactive contamination of pipelines, and therefore will not be repeated here.

In addition, in the aforementioned method 100 for calibrating and measuring radioactive contamination of a pipeline, and the system 200 for calibrating and measuring radioactive contamination of a pipeline, the radiation detector 500 can also be used to test radioactive contamination species in the pipeline. Referring to FIG. 9, the radiation detector 500 may also carry the cesium iodide crystal structure P. The cesium iodide crystal can detect the gamma ray spectrum inside the pipeline to identify radioactively contaminated key nuclear species such as cesium-137 or cobalt-60. .

The present invention has been disclosed in the foregoing with a preferred embodiment, but those skilled in the art should understand that this embodiment is only for describing the present invention, and should not be interpreted as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to this embodiment should be included in the scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the scope of the patent application.

100‧‧‧ Calibration and measurement method for radioactive contamination of pipeline

101 ~ 111‧‧‧ steps

200‧‧‧ Calibration and measurement system for radioactive pollution in pipelines

300‧‧‧ Calibration tube

400‧‧‧standard source

500‧‧‧ radiation detector

510‧‧‧detection window

520‧‧‧casters

600‧‧‧ Vehicle

610‧‧‧lighting unit

620‧‧‧ camera unit

700‧‧‧ processing unit

P‧‧‧Cesium iodide crystal structure

T‧‧‧ tube to be tested

FIG. 1 is a flowchart of steps of a method for calibrating and measuring radioactive contamination of a pipeline according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a tube to be tested and a calibration tube for a method of calibrating and measuring radioactive contamination of a pipeline according to the present invention; Schematic diagram of the standard radio source of the method for calibrating and measuring the radioactive contamination of the pipeline according to the present invention; FIG. 4A is a schematic diagram of the cylindrical radiation detector for the method of calibrating and measuring the radioactive contamination of the pipeline according to the present invention; Schematic diagram of a disc-shaped radiation detector for calibration and measurement of radioactive contamination; Figure 5 is a schematic diagram of a carrier for calibration and measurement of radioactive contamination of a pipeline according to the present invention; Figure 6 is calibration and measurement of radiocontamination of a pipeline shown in Figure 1 Schematic diagram of reaction efficiency correction of the method; Fig. 7 is a schematic diagram of the radiological counting rate measurement of the radioactive pollution correction and measurement method of Fig. 1; Fig. 8 is a structure of a radioactive pollution correction and measurement system of the pipeline according to another embodiment of the present invention. Block diagram; and FIG. 9 is a schematic diagram of a cesium iodide crystal structure carried by a radiation detector of the present invention.

Claims (10)

A method for calibrating and measuring radioactive contamination of a pipeline is used to measure a radioactive specific activity inside a tube to be measured. The method for calibrating and measuring radioactive contamination of a pipeline includes the following steps: A calibration tube is provided in the calibration tube. The wall has the same diameter as the inner wall of the tube to be tested; a standard radio source is provided, which has a standard radiation activity value of a nucleus; the standard radio source is laid on the inner wall of the calibration tube; a Radiation detector and a vehicle, and the vehicle is connected to the radiation detector; placing the radiation detector and the vehicle in the calibration tube; operating the radiation detector to measure the standard of the radiation nuclei The radiation activity value, and a corrected count rate of one of the standard radiation activity values is measured; a ratio of the corrected count rate to the standard radiation activity value is used to calculate a response efficiency of the radiation detector; The radiation detector and the vehicle are in the tube to be tested; the vehicle is operated to move the radiation detector in the tube to be tested; the radiation detector is operated to measure one of the tubes under test Radiation count rate ; And using the ratio of the radiation counting rate to the reaction efficiency to calculate the specific radioactivity of the tube to be tested. The method for calibrating and measuring radioactive contamination of pipelines as described in claim 1, wherein the standard radioactive source is cobalt-60, cesium-137, thorium-152 or thorium-241. The method for calibrating and measuring radioactive contamination of a pipeline according to claim 1, further comprising: providing a lighting unit and a camera unit; installing the lighting unit and the camera unit at the front end of the vehicle; operating the lighting unit to illuminate The inner wall of the tube under test; and operating the camera unit to capture an image of the inner wall of the tube under test. The method for calibrating and measuring radioactive contamination of a pipeline as described in claim 1, wherein the radiation detector is cylindrical or disc-shaped. The method for calibrating and measuring radioactive contamination of a pipeline as described in claim 1, further comprising: providing a plurality of casters and installing the casters on the radiation detector; and adjusting the positions of the casters so that each of the casters abuts against each other On the inner wall of the tube to be tested or the calibration tube, and to position the radiation detector at the center of the section of the tube to be tested or the calibration tube. A calibration and measurement system for radioactive contamination of a pipeline is used to measure a specific activity of radioactivity inside a tube to be measured. The calibration and measurement system for radioactive contamination of a pipeline includes: a calibration tube, an inner wall of the calibration tube and the The diameter of the inner wall of the tube to be measured is the same; a standard radiation source is laid on the inner wall of the calibration tube, and the standard radiation source has a standard radiation activity value of a radiation nuclei; a radiation detector with reactive radiation Response time, the radiation detector is used to measure the standard radiation activity value of the radiation nucleus and measure a corrected count rate, or measure a radiation count rate in the tube to be tested; a carrier, connected to the A radiation detector, and the carrier is movable on the inner wall of the calibration tube or the tube under test; and a processing unit, which calculates the reaction efficiency based on the ratio of the calibration count rate to the standard radiation activity value, The specific activity of the radioactivity is calculated based on the ratio of the radiological counting rate to the reaction efficiency. The calibration and measurement system for radioactive contamination of pipelines as described in claim 6, wherein the standard radiation source is cobalt-60, cesium-137, thorium-152 or thorium-241. The calibration and measurement system for radioactive contamination of pipelines according to claim 6, further comprising: a lighting unit provided at the front end of the vehicle, the lighting unit being used to illuminate the inner wall of the tube to be tested; and a camera unit, The camera unit is arranged at the front end of the vehicle, and the camera unit is used to capture the image of the inner wall of the tube to be tested. The calibration and measurement system for radioactive contamination of pipelines according to claim 6, wherein the radiation detector is cylindrical or disc-shaped. The correction and measurement system for pipeline radioactive pollution as described in claim 6, further comprising: a plurality of casters provided on the radiation detector, each of which casts against the inner wall of the tube to be tested or the calibration tube to The radiation detector is positioned at the center of the section of the tube to be tested or the calibration tube.