A nuclear emergency 131 I-Nucite Measurement Device and Remote Calibration Method

Abstract

Nuclear emergency 131 I Isotope measuring device and its remote calibration method, the method at least includes: in the standard environment: to 131 I Isotope at least two distance conditions of detection efficiency measurement, and establish 131 I Isotope and the detection efficiency relationship of the first reference isotope;In the remote calibration site and in the condition of energy calibration: measure the measured detection efficiency of one of the distance conditions of the first reference isotope with known activity, and determine 131 I Isotope measured detection efficiency in at least one distance condition;Compare 131 I Isotope measured detection efficiency with the corresponding detection efficiency is consistent or not.The present application completes the remote calibration of 131 I Isotope measuring device by using the reference isotope with long half-life and the detection efficiency relationship of the reference isotope and 131 I Isotope, without transporting high activity standard source to the site, solves the problem that 131 I Isotope is not easy to save due to short half-life.

Description

Technical Field

[0001] This invention belongs to the field of radioactivity measurement technology, and particularly relates to a nuclear emergency response method. 131 I-type nuclide measuring device and its remote calibration method. Background Technology

[0002] Nuclear safety is the lifeline for the sustainable and healthy development of the nuclear energy industry, and nuclear emergency response is the sum of actions taken to deal with nuclear accidents of all levels. Nuclear accidents or radioactive emergencies may cause radiation hazards to on-site emergency personnel and the public, and cause radioactive contamination of the surrounding environment, water sources, and food. Immediately after a nuclear or radioactive emergency, the emergency monitoring team should quickly conduct on-site contamination level investigations and dose monitoring (including internal and external radiation monitoring of exposed personnel, radioactive analysis of contaminated sites, and detection of radioactive contamination levels in drinking water and food), and promptly report the analysis results (generally within 24 hours) to facilitate rapid development of targeted emergency decisions and the implementation of correct nuclear emergency response measures. Rapid response is crucial for nuclear emergencies, and ensuring measurement accuracy is the foundation for correct decision-making. Accurate and consistent measurement values ​​in nuclear emergencies are conducive to rapid and accurate control of the accident source, reducing the severity of the accident, and minimizing losses. The main radionuclides in nuclear emergencies, besides... 3 H, 14 Apart from pure β or α nuclides such as C, more than 95% of nuclides, such as 131 I, 134 Cs、 137 Cs、 60 Co and other substances can be quantitatively measured by detecting gamma rays. This invention relates to a method for measuring gamma nuclides in nuclear emergency situations. 131 Remote calibration technology for I-meters is crucial for ensuring safety at nuclear emergency sites. 131 The accuracy of I nuclide measurements is extremely important.

[0003] The in-depth development and widespread application of nuclear energy and nuclear technology in my country have promoted the advancement of radiation protection and safety technologies. However, nuclear accidents and radioactive emergencies cannot be completely avoided. In the event of an accident, quickly identifying the type and dose of radionuclides in the bodies of contaminated individuals is crucial for rescue efforts and nuclear emergency response decisions. Historically, many nuclear power plant accidents have released large amounts of radioactive iodine into the environment. 131 I is one of the key nuclides with significant biological importance and harmful to the health of those who ingest it. In terms of medical emergency treatment for nuclear radiation accidents, it is found in the human thyroid gland. 131 Rapid and accurate measurement of thyroid hormone (I) is of great significance. Direct measurement of individual thyroid hormone is simple, easy to perform, and a mature and reliable method, compared to environmental monitoring-based methods. 131Compared to thyroid hormone (I) measurements, the uncertainty is much smaller, making it suitable for early and rapid screening and assessment of affected populations, providing technical support for emergency decision-making. Within a week of the Chernobyl accident, direct thyroid hormone measurements were performed on hundreds of thousands of people. Following the Fukushima nuclear accident in Japan, direct thyroid hormone measurements were also performed on children in surrounding areas. 131 I measure.

[0004] Therefore, in emergency response to nuclear accidents and radiological emergencies, the thyroid gland... 131 Accurate measurement of I activity is of paramount importance. Therefore, the methods used... 131 The accuracy of the I measuring instrument and the reliability of its calibration method are the fundamental guarantees for carrying out the above work.

[0005] Currently, in the human thyroid gland 131 The main way to quickly and accurately measure I is by using: 131 The I-meter directly measures the thyroid gland in the human body, and can directly obtain the contents of the thyroid gland. 131 The activity of I. This measurement method utilizes a thyroid analyzer based on the gamma detection principle. 131 The gamma rays emitted by I decay are accurately obtained after efficiency calibration, self-absorption correction, and distance correction. 131 I. Activity. For example, patent document CN215128840U provides a human thyroid gland measuring instrument, including a base, a measuring chair fixedly mounted on the base, and a multi-functional control frame; a detector and a data acquisition system are installed on the multi-functional control frame, and the detector is electrically connected to the data acquisition system; the detector is used to detect gamma radiation in the human thyroid gland and convert the detected photoelectric signal into a pulse signal; the data acquisition system is used to count the pulse signals. However, due to the emergency response to nuclear accidents and radioactive emergencies, in addition to 131 Besides I nuclides, there are generally also such as 134 Cs、 137 Cs、 60 Gamma-ray nuclides such as Co, whose decay releases gamma rays, can affect the measurement results of thyroid iodine analyzers based on gamma detection principles. However, it is difficult to transport heavy lead shielding to the nuclear emergency detection site, resulting in significant background radiation affecting the detector's accuracy. Consequently, calibration results obtained in the laboratory are no longer applicable at the nuclear emergency site. Furthermore, the presence of radioactive contamination makes complex measurement operations at the nuclear emergency site impractical. Therefore, remote calibration has become crucial for thyroid iodine analyzers. 131 The key to ensuring the measurement results of I-meters is... Conducting nuclear emergency response... 131 Research on remote calibration methods for I-type nuclide measuring instruments is of great significance.

[0006] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0007] In the existing technology, the human thyroid gland 131 The main way to quickly and accurately measure I is by using: 131 The I-meter directly measures the thyroid gland in the human body, and can directly obtain the contents of the thyroid gland. 131 The activity of I. This measurement method utilizes a thyroid analyzer based on the gamma detection principle. 131 The gamma rays emitted by I decay are accurately obtained after efficiency calibration, self-absorption correction, and distance correction. 131 I activity. However, due to the emergency response to nuclear accidents and radiological emergencies, in addition to 131 Besides I nuclides, there are generally also such as 134 Cs、 137 Cs、 60 Gamma-ray nuclides such as Co, whose decay releases gamma rays, can affect the measurement results of thyroid iodine analyzers based on gamma detection principles. However, it is difficult to carry heavy lead shielding to the nuclear emergency detection site, resulting in the detector's background being significantly affected by surrounding radiation. Consequently, calibration results obtained in the laboratory are no longer applicable at the nuclear emergency site. Furthermore, the presence of radioactive contamination makes complex measurement operations at the nuclear emergency site impractical. Therefore, how to calibrate thyroid iodine analyzers without using lead shielding remains an unsolved technical problem.

[0008] This invention aims to be based on 131 The relationship between the detection efficiency of nuclide I and other reference nuclides is calculated and accurately obtained by measuring the detection efficiency of the first reference nuclide at the remote calibration site. 131 The detection efficiency of I nuclides, thereby achieving 131 Remote calibration of the I-nuclide measuring instrument.

[0009] To address the shortcomings of existing technologies, this invention provides a nuclear emergency response method. 131 A remote calibration method for a radionuclide measuring device, characterized in that the method includes at least:

[0010] In a standard environment: For 131 I nuclides were used to measure detection efficiency under at least two distance conditions, and a system was established. 131 The relationship between the detection efficiency of nuclide I and the first reference nuclide;

[0011] At a remote calibration site and under energy calibration conditions: the measured detection efficiency of a first reference nuclide with known activity under one distance condition is measured, and the detection efficiency relationship is determined accordingly. 131 Measured detection efficiency of I nuclide under at least one distance condition;

[0012] Compare 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency?

[0013] In this invention, activities with different values ​​are obtained by using two significantly different distance conditions. 131 The detection efficiency of I nuclides has been improved, solving the problems of energy spectrum distortion and full-energy spectrum counting channel blockage caused by high activity. This invention is also based on... 131 Calculation of the detection efficiency relationship between I nuclide and reference nuclide in remote field 131 The measured detection efficiency of I nuclide can be obtained remotely in-situ without the need for lead shielding to create a standard environment. 131 The measured detection efficiency of I nuclide thus completes 131 Calibration of detection efficiency for I nuclides.

[0014] Preferably, the method further includes:

[0015] Energy calibration under standard conditions: Based on 131 Standard energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position:

[0016] E = A * X 2 +B*X+C, where E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants;

[0017] Energy calibration is performed at the remote calibration site: based on the reference peak position pair of the second reference nuclide. 131 Energy calibration is performed using the I-nuclide measurement device.

[0018] After energy calibration, the reference peak position of the nuclide can be obtained. At the remote calibration site, the measuring device can be calibrated according to the reference peak position, thereby improving the measurement accuracy of the measuring device.

[0019] Preferably, under standard conditions, when determining 131 Before describing the detection efficiency relationship between nuclide I and the first reference nuclide, background measurements are performed based on at least two distances and the background spectrum is preserved. 131The efficiency calibration of the I-nuclide measurement device is performed. The reason why the background spectrum is measured under two different distance conditions in this invention is that at close distance, the phantom is close to the probe surface and will block some of the ambient gamma rays, while at long distance, the phantom is far from the probe surface and will not block the ambient gamma rays from entering the detector. Therefore, the background of the measurement device will be different in the two modes.

[0020] The efficiency calibration method is as follows:

[0021] ε I Indicates the detection efficiency of a standard radioactive source; n I The total integral count rate of the background and nuclide source within the full-energy peak range of the characteristic gamma spectrum of a standard radioactive source; n b A represents the background integral count rate within the full-energy peak address range of the background energy spectrum; I P represents the activity of a standard radioactive source. I This indicates the proportion of gamma rays of a specific energy emitted by a radioactive source.

[0022] Preferably, determine 131 The relationship between the detection efficiency of nuclide I and the first reference nuclide is as follows:

[0023] ε I-131 =k*ε 第一参考核素

[0024] Where, ε I-131 and ε 第一参考核素 These represent the values ​​detected under the same distance conditions. 131 The detection efficiency of nuclide I and the first reference nuclide; k represents the correlation coefficient.

[0025] This invention calibrates the detection efficiency of the long-half-life nuclide Ba-133 during efficiency calibration. Leveraging its similar energy to I-131 and its long half-life, which allows for long-term preservation, the invention establishes a relationship between the detection efficiency of the measuring device for the two nuclides. After calibration, Ba-133 can be used instead of I-131 in routine efficiency monitoring tests, solving the problem of difficulty in monitoring the detection efficiency of the measuring device after efficiency calibration due to the short half-life and difficult preservation of I-131.

[0026] Preferably, the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position is used to... 131 Methods for energy calibration of I-nuclide measuring devices include:

[0027] At the remote calibration site, background measurements are performed based on at least two distances, and the background spectrum is saved.

[0028] The correctness of the energy calibration is determined based on a second reference nuclide in the environment;

[0029] If incorrect, recalibrate the energy until the measured peak position of the second reference nuclide after energy calibration matches the reference peak position during pre-energy calibration.

[0030] Preferably, in a remote calibration site, the method for determining the correctness of the energy calibration based on a second reference nuclide in the environment includes at least the following:

[0031] The peak position of at least one characteristic peak of at least one second reference nuclide is measured in advance as the reference peak position.

[0032] The measured peak position of the second reference nuclide was measured at the remote calibration site.

[0033] Compare the measured peak position with the corresponding reference peak position. If the measured peak position is consistent with the corresponding reference peak position, the energy calibration is considered correct.

[0034] In this invention, the correspondence between the characteristic peak energy of a nuclide and the reference peak position is obtained through energy calibration under a standard environment. This enables the measuring device to perform energy calibration at the remote calibration site, solving the problem that the nuclide measuring device cannot perform energy calibration at the remote calibration site.

[0035] Preferably, the method includes:

[0036] conduct 131 The detection efficiency measurement of I nuclides includes at least two distance conditions, including at least a first distance condition and a second distance condition, wherein the first distance condition is for measuring low activity. 131 The distance for nuclide I is 0–5 cm; the second distance condition is for measuring high activity. 131 The distance between I nuclides is 100–300 cm.

[0037] Unlike existing technologies, the data in this invention are measured and calculated under at least two distance conditions.

[0038] Preferably, the first reference nuclide is Ba-133, and the second reference nuclide is one or both of Ba-133 and K-40.

[0039] Ba-133 and I-131 nuclides have similar energies and long half-lives, giving them the advantage of long-term preservation. Using Ba-133 instead of I-131 will not affect the accuracy of the measurement results. K-40 nuclide is naturally occurring and always present. Energy and spectral shape calibration can be performed by comparing the peak positions of naturally occurring K-40 and a nuclide being calibrated (such as I-131). Using K-40 as a second reference nuclide helps to correct specific energy peaks to the correct positions, achieving spectral shape calibration and thus ensuring the accuracy of efficiency calibration.

[0040] This invention also provides nuclear emergency response. 131 I nuclide measuring device, including at least 131 I. Radionuclide measuring instrument body and efficiency calibration module 131 The I-nuclide measuring instrument body is connected to the efficiency calibration module.

[0041] Calibration module: used to record the measured detection efficiency when measuring the measured detection efficiency of a first reference nuclide with known activity under one of the distance conditions, and to determine based on the detection efficiency relationship. 131 Measured detection efficiency of I nuclide under at least one distance condition; comparison 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency?

[0042] The present invention 131 The I-nuclide measurement device can automatically store and calculate data, saving calculation time and reducing calibration complexity, making the device easy to operate and providing accurate measurement results.

[0043] Preferably, the device further includes an energy calibration module, which is connected to the storage module 7. Under standard conditions, the energy calibration module is based on... 131 Standard energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position: E = A * X 2 +B*X+C, where E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants; at the remote calibration site, the energy calibration module calibrates the source based on the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position. 131 Energy calibration is performed using the I-nuclide measurement device.

[0044] The energy calibration module of this invention can quickly calculate and obtain the corresponding relationship according to a preset formula, simplifying the energy calibration process.

[0045] Preferably, the device further includes 131 The instrument consists of the main body of the I-type radionuclide analyzer, a height-adjustable phantom support, the phantom, a standard radioactive source, and a calibration platform.

[0046] The calibration source is placed in the nuclide placement slot reserved in the phantom.

[0047] The mold body is placed in a specific orientation at the corresponding position on the height-adjustable mold body support.

[0048] The height-adjustable phantom support is movable in a movable manner so that the standard radiation source is aligned with the... 131 The distance between the probes of the I-nuclide measuring instrument can achieve at least two distance conditions, among which,

[0049] The calibration platform is equipped with features for indicating the relationship between the standard radioactive source and... 131 The distance indicator marks for at least two distances between the probe centers of the I-nuclide measuring instrument.

[0050] By setting an indicator mark for the detection distance, operators can accurately control the detection distance and ensure the accuracy of the measurement results. At the same time, when using this measuring instrument for actual measurement, it is also divided into high-activity long-distance measurement and low-activity short-distance measurement under the same conditions as during calibration, thereby improving the accuracy of the actual measurement results. Attached Figure Description

[0051] Figure 1 This invention is a preferred method for nuclear emergency response. 131 A schematic diagram of the modular structure of the I-nuclide measurement device;

[0052] Figure 2 This invention is a preferred method for nuclear emergency response. 131 A schematic diagram of the structure of the I-nuclide measuring device under the first distance condition;

[0053] Figure 3 This invention is a preferred method for nuclear emergency response. 131 A schematic diagram of the structure of the I-nuclide measuring device under the second distance condition.

[0054] List of reference numerals

[0055] 1: Detector source; 2: Phantom; 3: Energy calibration module; 4: Efficiency calibration module; 5: Measuring instrument body; 6: Phantom support; 7: Storage module; 8: Calibration platform. Detailed Implementation

[0056] The following is a detailed explanation with reference to the accompanying drawings.

[0057] 131 I is a radioactive isotope of element iodine, an artificial radionuclide produced by nuclear fission, with a half-life of 8.0252 days. It does not normally exist in nature. 131 I's. 131I decays by emitting beta rays with a maximum energy of 606.30 keV and gamma rays with a main energy of 364.49 keV. 131 I is highly volatile and belongs to a class of highly toxic radionuclides; it can be found in the air. 131 Once inhaled, I will continuously accumulate in the thyroid gland. 131 The beta rays released from the decay of I-rays continue to interact with the thyroid gland through ionizing radiation, causing internal radiation damage to the thyroid gland. This can eventually lead to thyroid dysfunction caused by internal radiation exposure, increasing the risk of thyroid cancer in those exposed.

[0058] 131 I is used in the hospital's nuclear medicine department as a drug for the diagnosis and treatment of thyroid diseases, and it is also one of the main nuclides used in occupational internal radiation health monitoring and nuclear emergency monitoring in the event of a radiation accident. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) 131 I is an unsealed radiopharmaceutical, and the nuclear medicine department is an unsealed workplace with easily volatile components. 131 I was inhaled by the radiation worker, causing the worker to suffer 131 For internal radiation exposure, occupational internal radiation health monitoring is required for workers. On the other hand, patients who receive treatment still have a certain amount of radioactive iodine remaining in their bodies upon discharge. According to relevant national regulations, this portion of the body's internal radiation... 131 I activity should be below 400 MBq. To reduce the external radiation dose to the public from nuclear medicine drugs carried by discharged patients, the source of radiation exposure should be controlled at the time of patient discharge. 131 The activity of I is within the safe limits; historically, many nuclear power plant accidents have released large amounts of radioactive iodine into the environment, including radioactive... 131 I is one of the key nuclides with significant biological importance and harmful to the health of those who ingest it. Currently, it is found in the human thyroid gland. 131 Research on the measurement of I activity mainly focuses on the three aspects mentioned above. Therefore, the human thyroid gland involved in the above fields... 131 Accurate measurement of I activity is crucial, but in these cases... 131 I has a relatively wide activity range, and is usually taken as... 131 I in the body 131 The activity of I radionuclide is several orders of magnitude higher than that required for occupational health monitoring and nuclear emergency response monitoring, and currently there is no suitable device that simultaneously meets the requirements of these measurement ranges. Therefore, it is necessary to provide a remote calibration method for a radionuclide measuring instrument that can simultaneously meet these requirements. 131 Occupational health monitoring, nuclear emergency response 131 I activity measurement and acceptance 131 Patients receiving I-drug therapy had their blood levels at discharge. 131 The need for I activity monitoring.

[0059] This invention provides a nuclear emergency response system. 131 The device for measuring I nuclides and its remote calibration method can also provide a remote automatic calibration method. 131 I-Nucleotide Measurement Apparatus and Calibration Method Thereof

[0060] In this invention, a standard environment refers to a laboratory environment or an environment that meets lead shielding requirements.

[0061] The first reference nuclide in this invention is preferably Ba-133, but is not limited to Ba-133. In the embodiments, Ba-133 is used as the first reference nuclide for illustrative purposes.

[0062] The second reference nuclide includes at least Ba-133 and K-40. In this example, K-40 is used as the second reference nuclide for illustration.

[0063] like Figure 1 As shown, a nuclear emergency 131 I nuclide measuring device, including at least 131 I. The main body of the radionuclide measuring instrument 5 and the efficiency calibration module 4. 131 The I-nuclide measuring instrument is connected to the efficiency calibration module 4. The connection methods of this invention include wired and wireless connections.

[0064] Preferably, if the measuring instrument body 5 does not include the storage module 7, the present invention may further include the storage module 7 to store any data information required by the measuring device. The storage module 7 can be connected to the efficiency calibration module 4 and the energy calibration module 3 respectively. The storage module 7 is connected to the measuring instrument body 5.

[0065] Storage module 7: Used to store detection efficiency measurements obtained under at least two distance conditions in a standard environment and 131 Relationship between the detection efficiency of the I nuclide and the first reference nuclide.

[0066] Calibration module: used to record the measured detection efficiency when measuring the measured detection efficiency of a first reference nuclide with known activity under one of the distance conditions, and to determine based on the detection efficiency relationship. 131 Measured detection efficiency of I nuclide under at least one distance condition; comparison 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency?

[0067] Preferably, nuclear emergency 131 The I-nuclide measurement device also includes an energy calibration module 3. Under standard conditions, the energy calibration module 3 is based on... 131 Standard energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position:

[0068] E = A * X 2 +B*X+C,

[0069] E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants;

[0070] At the remote calibration site, the energy calibration module 3, based on the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position, performs calibration... 131 Energy calibration is performed using the I-nuclide measurement device.

[0071] The efficiency calibration module 4 and the energy calibration module 3 in this invention can both be one or more of a processor, CPU, dedicated integrated chip, and server.

[0072] Preferably, the efficiency calibration module 4 and the energy calibration module 3 can be integrated into a dedicated integrated chip, processor, or server to simultaneously perform the functions of the efficiency calibration module 4 and the energy calibration module 3.

[0073] The storage module 7 in this invention includes, but is not limited to, one or more of the following: a chip with storage function, a magnetic medium, a hard disk, and a server.

[0074] Preferably, such as Figure 2 and Figure 3 As shown, nuclear emergency 131 The I-nuclide measuring device also includes 131 The apparatus comprises a radionuclide measuring instrument, a height-adjustable phantom support 6, a phantom 2, a standard radioactive source, and a calibration platform 8. The calibration source is placed in a pre-reserved radionuclide placement slot in the phantom 2. The phantom 2 is positioned in a specific orientation at a corresponding location on the height-adjustable phantom support 6. The height-adjustable phantom support 6 is movable so that the standard radioactive source is aligned with the phantom 2. 131 The distance between the probes of the I-type nuclide measuring instrument can achieve at least two distance conditions.

[0075] The calibration platform 8 is equipped with a feature for indicating the standard radioactive source and... 131 The distance indicator marks for at least two distances between the centers of the probes of the isotope measuring instrument. The distance indicator marks can be graphic, image, numerical, 3D marks, or a combination thereof. 3D marks include, for example, scratches, grooves, raised areas, three-dimensional marks, three-dimensional graphics, etc.

[0076] Nuclear emergency response of the present invention 131 The remote calibration method for the I-nuclide measurement device is described below. This invention will separately describe the operation method under standard conditions and the operation method under remote calibration site conditions.

[0077] Methods implemented in standard environments include:

[0078] S1: Yes131 I nuclides were used to measure the detection efficiency under at least two distance conditions;

[0079] S2: Perform pre-energy calibration to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position;

[0080] S3: Perform the first background measurement based on at least two distances and save the background spectrum;

[0081] S4: Perform the first efficiency calibration;

[0082] S5: Establish 131 Relationship between the detection efficiency of the I nuclide and the first reference nuclide.

[0083] Methods implemented in remote calibration sites include:

[0084] S6: The correspondence between the characteristic peak energy and the reference peak position of the second reference nuclide 131 Energy calibration is performed using the I-nuclide measurement device;

[0085] S7: Perform a second background measurement based on at least two distances and save the background spectrum;

[0086] S8: Perform a second efficiency calibration; measure the measured detection efficiency of a first reference nuclide with known activity under one distance condition, and determine the efficiency based on the aforementioned detection efficiency relationship. 131 Measured detection efficiency of I nuclide under at least one distance condition; comparison 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency?

[0087] S9: In 131 If the measured detection efficiency of the I nuclide is consistent with the corresponding detection efficiency, the remote calibration step is completed.

[0088] This invention provides a detailed description of each of the above steps.

[0089] S1: Measurement under at least two distance conditions 131 Measurement of detection efficiency of I nuclides.

[0090] The detection efficiency obtained under different distance conditions is stored in storage module 7.

[0091] like Figure 2 As shown, the first distance condition is for measuring low activity. 131 The distance for I nuclides is 0–5 cm, moving in 1 cm increments. Measurements of low activity... 131 The preferred first distance condition for nuclide I is 0 cm.

[0092] like Figure 3 As shown, the second distance condition is for measuring high activity.131 The distance between I nuclides is 100–300 cm, moving in 10 cm increments. Measurements of high activity... 131 The preferred second distance condition for nuclide I is 100 cm.

[0093] The distance measurement of this invention is not limited to the example; many more distances can be measured.

[0094] In existing technologies, nuclides are generally not calibrated across their full range. Calibration is typically performed using a radioactive source of moderate activity, and the efficiency of the measuring instrument is assumed to be linear. This calibration efficiency result is then used as the result for the entire measurement range, leading to poor accuracy when the measuring device ultimately uses the calibration efficiency result.

[0095] Since the primary measurement target of the thyroid measuring instrument is iodine isotopes, which have low gamma-ray energy, the detection distance and obstruction from objects significantly affect the detection efficiency. Under certain obstruction conditions, the distance between the standard detection source in phantom 2 and the probe of the measuring instrument will significantly and directly affect the instrument's detection efficiency in the calibration results. To ensure the quality of the calibration results, the detection distance must be controlled with precision down to the centimeter level. Therefore, this invention performs calibration at different distances. A different distance threshold is pre-set, and the calibration distance is automatically determined by judging the initial measurement count. When measuring at the first distance, i.e., the smaller distance, efficiency calibration is calculated using the count of the characteristic peak energy spectrum. When measuring at the second distance, i.e., the larger distance, efficiency calibration is calculated using the count of the full energy spectrum (the integrated count from channel 0 to the highest channel address), which solves the problem of energy spectrum distortion and counting channel blockage caused by high activity.

[0096] The activity of this invention refers to the number of atoms that decay per second in a radioactive element or isotope. The SI unit of radioactivity is the becquerel (Bq), which is one atom decays per second. One gram of radium has a radioactivity of 3.7 × 10⁻⁶. 10 Bq.

[0097] Low activity and high activity are each a range; the low activity range is: (10–7.4 × 10⁻⁶). 5 Bq; High activity range: (3.7 × 10⁻⁶) 5 ~7.4×10 8 )Bq.

[0098] For example, based on the distance indicator mark on the calibration platform 8, the support holding the phantom 2 is moved to a first position at a first distance (0 cm) from the probe to measure low activity. 131 The detection efficiency of nuclide I was measured. The support containing phantom 2 was moved to a second position, 100 cm away from the probe, and the high activity was measured. 131 Detection efficiency of I nuclides.

[0099] S2: Perform pre-energy calibration to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position.

[0100] The peak position of at least one characteristic peak of at least one second reference nuclide is measured in advance as a reference peak position. Preferably, the present invention can also perform energy calibration using nuclides such as I-125, Am-241, I-133, Cs137, Co-60 and K-40.

[0101] Energy calibration involves using gamma-ray sources with known energies to measure the peak positions at corresponding energies, and then plotting a curve showing the relationship between energy and peak position (channel address). With this curve, by measuring the gamma-ray energy peak position (channel address) of an unknown nuclide in a sample, the gamma-ray energy can be determined, thus identifying the nuclide species. After standard energy calibration, the correspondence between the characteristic peak energy and peak position (channel address) of a nuclide is obtained, thus establishing a nuclide database. Here, the peak position (channel address) obtained through energy calibration under standard conditions is referred to as the reference peak position.

[0102] During actual measurements, the energy spectrum of gamma rays emitted by the target nuclide will appear at the corresponding peak position (channel address), thus enabling automatic identification of the nuclide species. Only then can the detection efficiency be calculated to determine the nuclide activity. As shown in Tables 1 and 2, after energy calibration of the following nuclides, the iodine analyzer obtains the correspondence between the characteristic peak energy (information about the nuclide itself) and the reference peak position (the peak position displayed in the energy spectrum).

[0103] Table 1: Correspondence between characteristic peak energies and reference peak positions for various nuclides

[0104] Nuclide Characteristic peak energy (kev) Peak location (road) Road surface area (road) - peak width I-131 364.49 236 206-266 I-131 636.989 400 365-425 I-133 529.872 335 60 Cs-137 661.6 415 120 K-40 1460 900 110

[0105] Table 2: Basic characteristic information of each nuclide

[0106]

[0107] Specifically, the energy calibration module 3 is based on 131 Standard energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position:

[0108] E = A * X 2 +B*X+C, where E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants.

[0109] For example, when measuring the I-131 nuclide with known characteristic peak energies, the energies corresponding to its two peaks are known, namely 364.5 keV and 636.98 keV. Then, the energies corresponding to these peaks and their corresponding channel addresses are substituted into E = A*X. 2Adding B*X and C yields two equations. Furthermore, by measuring the k-40 nuclide with a known characteristic peak energy (1460 keV), we can substitute this peak energy and its corresponding channel address into E = A*X. 2 Adding B*X and C yields an equation. These three equations provide the specific values ​​of A, B, and C. In your subsequent energy calibration, based on the correspondence between the characteristic peak energy of the nuclide and the reference peak position, E = A*X... 2 By adding B*X+C, the channel address represented by the horizontal axis of the energy spectrum can be substituted and converted into energy for intuitive display.

[0110] S3: Perform the first background measurement based on at least two distances and save the background spectrum.

[0111] After pre-energy calibration in a standard environment, the first background measurement is performed.

[0112] Background measurements must be performed to ensure that there are no radioactive sources within the detector's range. The instrument's background primarily consists of unshielded ambient gamma rays and cosmic rays acting on the detector probe, resulting in the measured values. This background does not contribute to the standard detector source or the sample being tested. In actual measurements, the net count after deducting the instrument background should be used as the count result for activity calculation.

[0113] Preferably, two measurements are performed during the background measurement. At least the first distance for the low range and the second distance for the high range are measured separately.

[0114] Background measurements were performed at the first distance range, with phantom 2 maintained at 0 cm distance from the probe tip of the measuring instrument, for 10 minutes. Background measurements were then performed at the second distance range, with phantom 2 maintained at 100 cm distance from the probe tip of the measuring instrument, for 10 minutes. The background data was saved and stored in storage module 7 for use in efficiency calibration calculations.

[0115] The reason for measuring the background spectrum under two different distance conditions in this invention is that at close distances, the phantom 2 is close to the probe surface and will block some ambient gamma rays; at long distances, the phantom 2 is far from the probe surface and will not block ambient gamma rays from entering the detector. Therefore, the background of the measuring instrument will be somewhat different in the two modes. The shape of the background spectrum obtained under the two distances is the same, but the total integral count will be slightly different.

[0116] Methods for obtaining background data: Background data is used as subtracted data during standard detection source or sample measurement. Before calculation, the background must be measured, and the net count after background subtraction is used for relevant calculations. The background subtraction must correspond to the gamma peak count region involved in the actual sample measurement. For background measured at the second interval, the gamma count selected during actual sample or standard detection source measurement is the full energy spectrum (0 to the highest channel address). In this case, the background data should use the full energy spectrum of the background energy spectrum for calculation. For background measured at the first interval, the gamma count selected during actual sample or standard detection source measurement is a specific gamma-ray energy peak (counts within a certain range to the left and right of the channel address where the energy peak is located). In this case, the background data should use the counts within the channel address range where the gamma-ray energy peak is located for calculation.

[0117] S4: Perform the first efficiency calibration.

[0118] The purpose of efficiency calibration is to determine the relationship between detection efficiency and gamma-ray energy. Detection efficiency is further divided into full-spectrum detection efficiency and full-energy peak detection efficiency. Full-spectrum detection efficiency is generally used when the measuring instrument has poor energy resolution of the spectrum, and the integrated count of all channels from 0 to the highest channel (1023) is used as the measurement result for calculation. Full-energy peak detection efficiency is calculated by integrating the count of a certain gamma-ray energy peak of the measured object. The number of gamma rays of a certain energy (or all energies) emitted per unit time by the measured radioactive source (sample) is called the emissivity (N). The net number of gamma rays of that energy recorded by the measuring instrument per unit time (n) (after deducting the corresponding background number) is (n... b The count rate is the full-energy peak (or full spectrum). The ratio of the two is the gamma-ray detection efficiency (ε) for that energy (or all energies).

[0119] The calculation formula is as follows:

[0120]

[0121] In this invention, during efficiency calibration, the phantom 2 is first positioned at a distance from the probe of the distance measuring instrument, and the measurement is performed for 10 minutes. After the measurement is completed, the data is saved as a nuclide measurement file and stored in the storage module 7, and the energy spectrum is analyzed.

[0122] Because of pre-calibration of energy, the known peak energy of nuclides appears at the corresponding channel addresses. The 364.49 keV peak energy of nuclide I-131 appears at channel 236. The net count rate (measured by the count rate n when active) within its peak energy range (channels 206 to 236) is taken. I The background count rate n when there is no source b (Calculated from the difference). The activity of the radioactive source is known as A. IThe net number emissivity of gamma rays of this energy emitted per unit time by the measured radioactive source is also a known quantity, denoted as A. I *P I Among them, P I This refers to the branching ratio of gamma rays of that energy, which is the proportion of gamma rays of that energy emitted by the radioactive source among various energy gamma rays.

[0123] The formula for calculating the detection efficiency using the 364.46 keV energy peak of the I-131 nuclide is as follows:

[0124]

[0125] n I The total integral count rate of the background and nuclide source within the full-energy peak range of the characteristic gamma spectrum of a standard radioactive source; n b A represents the background integral count rate within the full-energy peak address range of the background energy spectrum; I P represents the activity of a standard radioactive source. I This indicates the proportion of gamma rays of a specific energy emitted by a radioactive source.

[0126] Similarly, the detection efficiency of other γ nuclides is determined according to the efficiency calibration formula, thereby achieving efficiency calibration of the measuring device.

[0127] During efficiency calibration, the sodium iodide probe of the measuring device may exhibit peak position drift in the energy spectrum. Therefore, energy calibration module 3 is used to correct the peak positions during calibration. This invention primarily utilizes the naturally occurring K-40 nuclide and the nuclide being calibrated (e.g., I-131) to correct the peak positions and calibrate the spectrum shape. The measuring device, having undergone pre-energy calibration, has known energy spectrum addresses for these energies, which are stored in a database. During measurement, the calibration module automatically identifies the peak positions. K-40 is always present in the energy spectrum, and the nuclide being calibrated is known (e.g., I-131). When the measuring instrument calibrates, it identifies two or more energy peaks, and energy calibration module 3 automatically identifies the nuclides corresponding to these peak positions.

[0128] The energy calibration module 3 compares the energy peak address of the nuclide in the storage module 7 to calculate the required energy gain adjustment. By adjusting the energy gain, the energy calibration module 3 corrects the specific energy peak to the correct position, achieving spectral shape calibration and thus ensuring the accuracy of efficiency calibration.

[0129] S5: Establishment of Detection Efficiency Module 131 Relationship between the detection efficiency of the I nuclide and the first reference nuclide.

[0130] Because I-131 nuclide has a short half-life of only 8.0252 days, the standard detector source 1 for I-131 will decay to almost nothing after a period of time (10 half-lives). Obtaining an I-131 nuclide source is inconvenient when monitoring the efficiency of the measuring instrument after calibration. Therefore, during instrument calibration, this invention uses Ba-133 nuclide (half-life 10.551 years, gamma-ray energy 356 keV), which has a similar energy to I-131 nuclide but a longer half-life, for measurement, and simultaneously performs efficiency calibration to establish the efficiency relationship between the measuring instrument and I-131 nuclide and Ba-133 nuclide. The first reference nuclide in this case is Ba-133 nuclide. The first reference nuclide of this invention is not limited to Ba-133 nuclide; it can also be other nuclides with similar properties to Ba-133 nuclide.

[0131] Sure 131 The relationship between the detection efficiency of nuclide I and the first reference nuclide is as follows:

[0132] ε I-131 =k*ε 第一参考核素

[0133] Where, ε I-131 and ε 第一参考核素 These represent the values ​​detected under the same distance conditions. 131 The detection efficiency of nuclide I and the first reference nuclide; k represents the correlation coefficient.

[0134] Existing efficiency detection methods do not establish a detection efficiency relationship between Ba-133 and I-131 nuclides, making routine efficiency monitoring measurements impossible to perform at any time. These measurements can only be conducted when a standard I-131 detector source with suitable activity is available. The efficiency calibration method of this invention enables real-time monitoring and testing of the instrument's detection efficiency, thereby ensuring the accuracy of the instrument's calibration efficiency at all times.

[0135] Specifically, the present invention establishes [the following conditions] under the first distance condition and the second distance condition respectively. 131 Relationship between the detection efficiency of the I nuclide and the first reference nuclide.

[0136] A measurement was performed when the distance between the Ba-133 nuclide source and the measuring instrument probe was the first distance (0 cm), and the relationship ε was obtained. I-131s =k1*ε Ba-133s .

[0137] ε I-131s This represents the detection efficiency of the I-131 nuclide under the first distance condition. ε Ba-133sThis represents the detection efficiency of Ba-133 nuclide under the first distance condition. k1 represents the correlation coefficient. The efficiency calibration module 4 records or sends the detection efficiency relationship under the first distance condition to the storage module 7 for storage.

[0138] A measurement was performed when the distance between the Ba-133 nuclide source and the measuring instrument probe was the second distance (100cm), and the relationship ε was obtained. I-131l =k2*ε Ba-133l .

[0139] ε I-131l This indicates the detection efficiency of the I-131 nuclide under the second distance condition. ε Ba-133l This indicates the detection efficiency of Ba-133 nuclide under the second distance condition. k2 represents the correlation coefficient. The efficiency calibration module 4 records or sends the detection efficiency relationship under the second distance condition to the storage module 7 for storage.

[0140] This invention leverages the long-term preservation capability of the first reference nuclide to establish a relationship between the detection efficiency of the measuring instrument for two nuclides. After calibration, this allows for ongoing monitoring and testing of the measuring instrument's detection efficiency during routine use. This invention addresses the difficulty in monitoring and testing the measuring instrument's detection efficiency after efficiency calibration due to the short half-life and difficulty in preserving the I-131 nuclide.

[0141] S6: The correspondence between the characteristic peak energy and the reference peak position of the second reference nuclide 131 Energy calibration is performed using the I-nuclide measurement device.

[0142] At the remote calibration site, the correctness of the energy calibration is determined based on a second reference nuclide in the environment.

[0143] Specifically, the measured peak position of the second reference nuclide is measured at the remote calibration site. The measured peak position is compared with the corresponding reference peak position. If the measured peak position matches the corresponding reference peak position, the energy calibration is considered correct. If not, the on-site energy calibration is performed again until the measured peak position of the reference nuclide after energy calibration matches the reference peak position during the pre-energy calibration.

[0144] At this point, the second reference nuclide can be either K-40 or Ba-133.

[0145] At the remote calibration site, the second reference nuclide is subjected to on-site energy spectrum measurements under both the first and second distance conditions. For example, the peak positions of the characteristic peaks at 1460.82 keV for K-40 and / or 356.01 keV for Ba-133 are used as the measured peak positions. It is then determined whether the measured peak positions match the corresponding reference peak positions obtained under standard conditions. If they match, no energy spectrum correction is required. If they do not match, energy spectrum correction is necessary.

[0146] During energy spectrum correction, the gain and shift of the energy calibration curve are calculated using the measured peak position and the reference peak position, and the energy spectrum is corrected to the original, more accurate gain and shift.

[0147] The method for performing energy calibration on-site is as follows:

[0148] For the collected energy spectra (K-40 and Ba-133 nuclides), the peak position of the characteristic peak at 1460.82 kev for K-40 nuclide is identified as P1460; and the peak position of the characteristic peak at 356.01 kev for Ba-133 nuclide is identified as P356. Based on these two peak positions, the gain G1 and offset O1 of the energy calibration curve are calculated using the following formula.

[0149]

[0150] During on-site energy spectrum measurements, the energy spectrum is corrected to the fixed (under standard conditions) energy calibration curve parameters G0 and offset O0 based on gain G1 and offset O1. The new energy spectrum address is calculated according to the following formula:

[0151]

[0152] ch old Indicates the old energy spectrum address; ch new This indicates the new energy spectrum address.

[0153] S7: Perform a second background measurement based on at least two distance conditions and save the background spectrum.

[0154] Preferably, two measurements are performed during the background measurement. At least the first distance for the low range and the second distance for the high range are measured separately.

[0155] Background measurements were performed at the first distance range, with phantom 2 maintained at a 2cm distance from the probe tip of the measuring instrument, for 10 minutes. Background measurements were then performed at the second distance range, with phantom 2 maintained at a 100cm distance from the probe tip of the measuring instrument, for 10 minutes. The background data was saved and stored in storage module 7 for use in efficiency calibration calculations.

[0156] S8: Perform a second efficiency calibration.

[0157] The measured detection efficiency of a first reference nuclide with known activity is determined under one distance condition. Preferably, the measured detection efficiency of the first reference nuclide with known activity is determined under a first distance condition. For example, the measured detection efficiency of Ba-133 nuclide with known activity is determined under a first distance condition. The efficiency calibration module 4 calculates the efficiency based on the detection efficiency relationship under the first distance condition. 131 Measured detection efficiency of I nuclide under the first distance condition.

[0158] Efficiency calibration module 4 comparison 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency?

[0159] If the measured detection efficiency matches the corresponding detection efficiency, then efficiency calibration is not required. The measuring device is functioning normally and can be used directly.

[0160] If the measured detection efficiency differs from the corresponding detection efficiency, recalibration is required. The efficiency calibration module 4 calculates the efficiency based on the determined detection efficiency relationships under the first and second distance conditions. 131 The real-time detection efficiency of I nuclide under the first and second distance conditions is measured and updated to complete the remote efficiency calibration.

[0161] S9: In 131 The measured detection efficiency of nuclide I is consistent with the corresponding detection efficiency, thus completing the remote calibration step.

[0162] Thus, this invention completes the remote calibration of the measuring device at the remote calibration site by measuring the Ba-133 nuclide and related calculations, without the need to transport the high-activity standard detector to the site.

[0163] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention. These solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A nuclear emergency response 131 The remote calibration method for a radionuclide measuring device is characterized by... The method includes at least: In a standard environment: right 131 I nuclides were used to measure detection efficiency under at least two distance conditions, and Establish 131 The detection efficiency relationship between nuclide I and the first reference nuclide was determined. 131 The relationship between the detection efficiency of nuclide I and the first reference nuclide is as follows: e I-131 =k*e 第一参考核素 , Where, ε I-131 and ε 第一参考核素 These represent the values ​​detected under the same distance conditions. 131 Detection efficiency of nuclide I and the first reference nuclide; k represents the correlation coefficient; In the case of remote calibration without lead shielding and under energy calibration conditions: The measured detection efficiency of a first reference nuclide with known activity under one distance condition is determined, and the detection efficiency relationship is used to determine... 131 Measured detection efficiency of I nuclide under at least one distance condition; Compare 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency? 2. Nuclear emergency response as described in claim 1 131 The remote calibration method for a radionuclide measuring device is characterized by... The method further includes: Pre-energy calibration under standard conditions: Based on 131 Standard energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position: E=A*X 2 +B*X+C, E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants; Energy calibration is performed at the remote calibration site: based on the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position. 131 Energy calibration is performed on the I-nuclide measurement device.

3. Nuclear emergency response as described in claim 2 131 The remote calibration method for a radionuclide measuring device is characterized by... In a standard environment, in determining 131 Before describing the detection efficiency relationship between nuclide I and the first reference nuclide, background measurements are performed based on at least two distances and the background spectrum is preserved. 131 The efficiency calibration of the I-nuclide measurement device is performed, among which... The efficiency calibration method is as follows: ε I Indicates the detection efficiency for a standard radioactive source; n I The total integral count rate of the background and nuclide source within the full-energy peak range of the characteristic gamma spectrum of a standard radioactive source; n b This represents the background integral count rate within the full-energy peak address range of the background energy spectrum; A I P represents the activity of a standard radioactive source. I This indicates the proportion of gamma rays of a specific energy emitted by a radioactive source.

4. Nuclear emergency response as described in claim 3 131 The remote calibration method for a radionuclide measuring device is characterized by... Based on the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position, 131 Methods for energy calibration of I-nuclide measuring devices include: At the remote calibration site, background measurements are performed based on at least two distances, and the background spectrum is saved. The correctness of the energy calibration is determined based on a second reference nuclide in the environment; If incorrect, recalibrate the energy until the measured peak position of the second reference nuclide after energy calibration matches the reference peak position during pre-energy calibration.

5. Nuclear emergency response as described in claim 4 131 The remote calibration method for a radionuclide measuring device is characterized by... In remote calibration sites, methods for determining the correctness of energy calibration based on a second reference nuclide in the environment include at least the following: The peak position of at least one characteristic peak of at least one second reference nuclide is measured in advance as the reference peak position. The measured peak position of the second reference nuclide was measured at the remote calibration site. Compare the measured peak position with the corresponding reference peak position. If the measured peak position is consistent with the corresponding reference peak position, the energy calibration is considered correct.

6. Nuclear emergency response as described in claim 5 131 The remote calibration method for a radionuclide measuring device is characterized by... The method includes: conduct 131 The detection efficiency measurement of I nuclides requires at least two distance conditions, including at least a first distance condition and a second distance condition. The first distance condition is for measuring low activity. 131 The distance between I nuclides is 0–5 cm; The second distance condition is for measuring high activity. 131 The distance between I nuclides is 100–300 cm.

7. Adopting the nuclear emergency response method as described in any one of claims 1 to 6 131 The remote calibration method for the I-nuclide measurement device is used for calibration. 131 I-nuclide measuring device, characterized in that, At least including 131 I-type radionuclide measuring instrument body and efficiency calibration module, 131 The I-nuclide measuring instrument body is connected to the efficiency calibration module. Efficiency calibration module: used to record the measured detection efficiency when measuring the measured detection efficiency of a first reference nuclide with known activity under one of the distance conditions, and to determine the efficiency based on the measured detection efficiency relationship. 131 Measured detection efficiency of I nuclide under at least one distance condition; Compare 131 Does the measured detection efficiency of I nuclide match the corresponding detection efficiency? 8. As described in claim 7 131 I-nuclide measuring device, characterized in that, It also includes an energy calibration module. Under standard conditions, the energy calibration module is based on 131 Energy calibration is performed on at least three energy points of the I nuclide and the second reference nuclide to establish the correspondence between the characteristic peak energy of the nuclide and the reference peak position: E=A*X 2 +B*X+C, E represents the energy of the nuclide source, X represents the channel address, and A, B, and C represent constants; At the remote calibration site, the energy calibration module performs calibration based on the correspondence between the characteristic peak energy of the second reference nuclide and the reference peak position. 131 Energy calibration is performed on the I-nuclide measurement device.

9. As described in claim 7 or 8 131 I-nuclide measuring device, characterized in that, It also includes a height-adjustable phantom support, a phantom, a standard radiation source, and a calibration platform. The standard radioactive source is placed in the nuclide placement slot reserved in the phantom. The mold body is placed in a specific orientation at the corresponding position on the height-adjustable mold body support. The height-adjustable phantom support is movable so that the standard radiation source is positioned relative to the... 131 The distance between the probes of the I-nuclide measuring instrument can achieve at least two distance conditions, among which, The calibration platform is equipped with features for indicating the relationship between the standard radioactive source and... 131 Distance indication marks for at least two distances between the probe centers of the I-nuclide measuring instrument body.

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