A nuclear field nondestructive gamma measurement device based on a NaI detector and a measurement method

Abstract

The present application relates to a kind of nuclear field nondestructive gamma measurement device and method based on NaI detector, the method includes measuring and recording background signal reference value in shielding box, after sample measurement, net signal is obtained using background deduction algorithm, and the accurate processing of spectral data is realized through multiple smoothing and optimized energy resolution calculation.The present application does not need to destructively sample or chemical treatment to sample, by directly measuring gamma ray signal, the generation of secondary waste is avoided, with environmental protection advantage.The present application is especially suitable for the rapid nondestructive testing of nuclear power plant worker shoes and other samples, and the control precision is high, and the detection level of 2 minutes can reach 1e-2Bq / g.The measurement process of the present application is simple, and operation is flexible, suitable for laboratory and multiple scene uses on site.

Description

Technical Field

[0001] This invention relates to the field of nuclear measurement technology, and in particular to a non-destructive gamma measurement device and method based on a NaI detector in the nuclear field. Background Technology

[0002] Gamma-ray measurement technology is widely used in nuclear energy, environmental monitoring, and radiation protection. Traditional methods mainly include scintillation detectors, high-purity germanium detectors, and Geiger-Muller counters. These techniques have certain advantages in the detection of radionuclides, but they also have limitations.

[0003] Scintillation detectors utilize the flash effect of NaI(Tl) crystals for gamma-ray measurement, offering high sensitivity and a wide range of applications. However, their low energy resolution makes it difficult to accurately distinguish the characteristic energies of nuclides. High-purity germanium detectors, while possessing extremely high energy resolution, are complex, expensive, and require cryogenic operation, making them unsuitable for rapid on-site screening. Geiger-Muller counters are simple to operate and suitable for detecting high-intensity radiation sources, but their extremely low energy resolution makes them unsuitable for gamma-ray spectroscopy analysis.

[0004] Regarding the use of radionuclides in low-level contamination scenarios (such as on the shoes of nuclear power plant workers) 60 Traditional methods for non-destructive testing of low-activity nuclear contamination (Co < 0.1 Bq) all face limitations. For example, handheld radiation detectors lack sufficient sensitivity for low-activity measurements, and HPGe spectrometers require on-site sampling and transportation, a complex and time-consuming process. Furthermore, the limited sensitivity of existing detection equipment may lead to reduced accuracy and efficiency, making it difficult to meet the needs of rapid screening at nuclear power plants. Therefore, there is an urgent need for a new, efficient, sensitive, portable, and high-precision gamma-ray measurement technology to address the challenges of detecting low-activity nuclear contamination.

[0005] In view of the above problems, this invention is proposed. Summary of the Invention

[0006] This invention discloses a non-destructive gamma measurement device and method based on a NaI detector in the nuclear field, aiming to solve the technical problems existing in the prior art.

[0007] The present invention provides a nuclear-domain non-destructive gamma measurement method based on a NaI detector, comprising:

[0008] Without placing the sample to be measured, the NaI detector was placed in a shielded box, and the background signal reference value was measured and recorded.

[0009] The sample to be measured is placed in the measurement area of ​​the NaI detector, and the first measurement result of the sample is measured and recorded.

[0010] The second measurement result is obtained by subtracting the baseline from the first measurement result and the baseline signal reference value, using the following formula:

[0011]

[0012] in:

[0013] P smooth (E) is the smoothed spectrum;

[0014] N is the window size;

[0015] i is the index in the window;

[0016] P measured (E)=P signal (E)+P backgruond (E)

[0017] in:

[0018] P measured (E) is the measured total spectrum;

[0019] P signal (E) is the signal spectrum of the target source;

[0020] P backgruond (E) is the background spectrum;

[0021] The second measurement result is processed to obtain the final third measurement result, using the following formula:

[0022]

[0023] in:

[0024] P(E) is the count rate (spectral data) at energy E;

[0025] A is the peak height (maximum count), representing the signal strength;

[0026] E0 is the center energy of the peak (corresponding to the characteristic γ energy of the nuclide);

[0027] σ is the peak width, which is related to the energy resolution of the NaI detector.

[0028] As a preferred technical solution, before measuring and recording the first measurement result of the sample, the detection limit and detection time parameters of the NaI detector are calculated, and the NaI detector is set according to the parameters. The calculation formula is as follows:

[0029]

[0030] in:

[0031] Lmin It is the minimum detection limit;

[0032] K is a constant that depends on the sensitivity of the detector;

[0033] B represents background noise;

[0034] t is the detection time;

[0035] N signal and N background These are the counts of the signal and the background, respectively.

[0036] As a preferred technical solution, the detection time t is determined based on the content... 60 The accuracy of the control system for the work shoes of nuclear power plant workers in Co was determined.

[0037] As a preferred technical solution, the control accuracy is 1e-2Bq / g after 2 minutes of measurement.

[0038] As a preferred technical solution, the shielding box includes a shielding box body, the side wall of which has a through hole, and the top of the NaI detector is set as a cylinder, which contacts the outside of the shielding box through the through hole.

[0039] As a preferred technical solution, the nuclear electronics section of the NaI detector is equipped with a main amplifier circuit.

[0040] As a preferred technical solution, the main amplifier circuit includes a voltage amplifier, a first connector, and a second connector. The voltage amplifier is equipped with an operational amplifier U19, a feedback resistor R74, and an input resistor R68 for signal amplification. The first connector and the second connector are used to transmit the amplified signal to the outside.

[0041] As a preferred technical solution, the input resistor R68 is connected to the inverting input terminal of the operational amplifier U19, and the non-inverting input terminal of the operational amplifier U19 is grounded.

[0042] As a preferred technical solution, the size of the shielding box is 200mm×400mm×75mm.

[0043] As a preferred technical solution, the shielding box is equipped with a lead plate with a thickness of 4-7mm.

[0044] The technical solution adopted in this invention can achieve at least one of the following beneficial effects:

[0045] 1. This invention significantly improves detection efficiency by combining a NaI detector with a shielding box. Through background subtraction algorithms and multiple smoothing processes, accurate gamma-ray spectrum data can be obtained quickly, effectively reducing the minimum detection limit (L_min) and meeting the accuracy requirements for nuclear power plant workers' work shoes, thus achieving a dual improvement in measurement efficiency and accuracy. Furthermore, by employing an optimized energy resolution formula, characteristic gamma-ray energy peaks can be accurately identified, improving the ability to distinguish radionuclides.

[0046] 2. The measurement method of this invention eliminates the need for destructive sampling and sample preparation, directly measuring gamma rays through a NaI detector, thus avoiding physical damage or chemical treatment of the sample. Furthermore, it requires no other reagents or auxiliary materials, and the measurement process does not generate secondary waste, exhibiting strong environmental friendliness. This non-destructive measurement method significantly simplifies the process and is suitable for the rapid detection of various radioactive wastes, especially for rapid on-site screening at nuclear power plants.

[0047] 3. This invention features a miniaturized design, equipped with a compact shielding box and a highly efficient shielding structure with an internal lead plate, measuring 200mm × 400mm × 75mm, making it easy to carry and transport. Furthermore, the simplified operation process allows for completion of the measurement task simply by placing the sample in the shielding box, connecting it to the host computer, and initiating the measurement, significantly reducing operational complexity. This design is particularly suitable for use in laboratories, field settings, or other confined spaces, providing flexibility and convenience. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0049] Figure 1 This is a three-dimensional structural schematic diagram of a non-destructive gamma measurement device in the nuclear field based on a NaI detector according to the present invention;

[0050] Figure 2 This is a schematic diagram of the main amplifier circuit for the NaI detector of the present invention;

[0051] Figure 3 The graph shows the detection efficiency results of the simulation of the nuclear electronics part of the NaI detector using the Geant4 software of this invention.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1. Shielding box; 11. Shielding cover; 12. Shielding box body; 2. NaI detector; 3. Main amplifier circuit; 31. Voltage amplifier; 32. First connector; 33. Second connector. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0056] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0057] To address the problems existing in the prior art, embodiments of the present invention provide a non-destructive gamma measurement device for the nuclear field based on a NaI detector, particularly relating to an application scenario of full-material measurement of radioactive materials in work shoes worn by nuclear power plant workers, such as... Figure 1 As shown, the device includes a shielding box 1 and a NaI detector 2. The shielding box 1 provides radiation shielding, reducing interference from scattered gamma rays in the environment and ensuring accurate and reliable gamma ray measurements. The NaI detector 2 detects gamma rays and converts the ray signal into an electrical signal to achieve quantitative measurement of radiation intensity. The shielding box 1 has a shielding cover 11 and a shielding box body 12. During measurement, the shielding cover 11 is opened, and the NaI detector 2 is placed inside the shielding box body 12. To accommodate the external connection of the NaI detector 2, a through hole is provided on the side wall of the shielding box body 12 to allow the cylindrical top of the NaI detector 2 to protrude. To match the size requirements of the work shoes worn by nuclear power plant workers, the shielding box 1 is preferably 200mm × 400mm × 75mm. More preferably, to increase the radiation shielding effect, a lead plate with a thickness of 4-7mm is provided inside the shielding box 1.

[0058] In some preferred embodiments, the nuclear electronics section of the NaI detector 2 includes a voltage divider, a high-voltage generation circuit, a preamplifier circuit, a pole-zero cancellation circuit, a main amplifier circuit, and an FPGA digital circuit. Through integration, it achieves a complete functional integration from gamma-ray signal detection to digital signal processing. The voltage divider and high-voltage generation circuit ensure stable operation of the NaI detector 2; the preamplifier and pole-zero cancellation circuit improve signal accuracy and signal-to-noise ratio; the main amplifier enhances signal amplitude to accommodate subsequent processing; and the FPGA digital circuit enables efficient data acquisition and processing, improving the real-time performance, reliability, and integration of the NaI detector 2, and significantly optimizing measurement performance.

[0059] In some preferred embodiments, the main amplifier circuit 3 includes a voltage amplifier 31, a first connector 32, and a second connector 33, such as Figure 2 As shown, voltage amplifier 31 includes operational amplifier U19, which forms a fixed gain of 8 through feedback resistor R74 and input resistor R68. The input signal is connected to the inverting input terminal of operational amplifier U19 through input resistor R68, and the non-inverting input terminal of operational amplifier U19 is grounded. High-precision resistor R74 is used for feedback, and load matching resistor R69 is connected to the output terminal of operational amplifier U19 to ensure output impedance matching and avoid signal reflection. The main amplifier circuit 3 uses a ±5V dual power supply, and power supply decoupling capacitors C136 and C138 are used to filter out power supply noise. The final amplified signal is output through the AMP_OUT port and transmitted to other locations or external devices through first connector 32 or second connector 33. First connector 32 is a 2-pin connector for transmitting the amplified signal externally; second connector 33 is an SMA connector for connecting to external devices or test equipment to transmit the amplified signal externally.

[0060] In some preferred embodiments, the nuclear electronics section of the NaI detector 2 was simulated using LTspice software for some circuits, and Geant4 software was used to simulate important parameters such as detection efficiency. Figure 3 As shown, the Geant4 software simulates the detection efficiency of the nuclear electronics section of the NaI detector 2 in this embodiment of the invention, in order to optimize the nuclear electronics section of the NaI detector 2.

[0061] The present invention also provides a measurement method based on the above-mentioned non-destructive gamma measurement device in the nuclear field, comprising:

[0062] S1: Conduct baseline measurements;

[0063] S11: Place the NaI detector 2 in the shielding box 1, and ensure that no sample to be measured is placed in the shielding box 1, while ensuring that there is no interference from any radioactive material in the surrounding area.

[0064] S12: Turn on the power to NaI detector 2 and perform initialization settings;

[0065] S13: Perform the measurement without placing the sample to be measured, and record the measurement time and environmental conditions, including temperature and humidity, for later correction of the detection data;

[0066] S14: After the measurement is completed, turn off NaI detector 2 and record the obtained background signal reference value;

[0067] S2: Perform sample measurement;

[0068] S21: Place the sample to be measured in the measurement area of ​​NaI detector 2 and place them together in shielding box 1. Adjust the position and distance between the sample to be measured and NaI detector 2 to ensure that the detection efficiency is approximately the same for each measurement.

[0069] S22: Set the measurement time and parameters according to the experimental requirements and sample properties; with... 60 Taking the work shoes of nuclear power plant workers as an example, a measurement of 1e-2 Bq / g can be achieved in 2 minutes. This accuracy is sufficient to de-control the work shoes. At this point, the detection limit and detection time of the NaI detector 2 can be calculated using the following formulas:

[0070]

[0071] in:

[0072] L min It is the minimum detection limit

[0073] K is a constant that depends on the sensitivity of the detector.

[0074] B is background noise.

[0075] t is the detection time

[0076] N signal and N background These are the counts of the signal and the background, respectively.

[0077] S23: Perform measurements on the sample to be measured and record relevant data such as measurement time, sample information, and environmental conditions;

[0078] S24: After the measurement is completed, turn off NaI detector 2 and record the first measurement result;

[0079] S3: Process the above data to obtain the corrected third measurement result;

[0080] S31: Based on the baseline signal value and the first measurement result of the sample in steps S1 and S2, perform background subtraction on the first measurement result of the sample to obtain the pure sample signal, i.e., the second measurement result. The background subtraction is performed using the following formula:

[0081]

[0082] Among them, P smooth (E) is the smoothed spectrum, N is the window size, and i is the index in the window.

[0083] P measured (E)=P signal (E)+P backgruond (E)

[0084] Among them, P measured (E) is the measured total spectrum, P signal (E) is the signal spectrum of the target source, P backgruond (E) is the background spectrum.

[0085] S32: Perform data analysis and processing on the sample signal after background subtraction, including steps such as nuclide peak identification and fitting, and net count calculation. The algorithm is as follows:

[0086]

[0087] in:

[0088] P(E) is the count rate (spectral data) at energy E.

[0089] A is the peak height (maximum count), representing the signal strength.

[0090] E0 is the center energy of the peak (corresponding to the characteristic γ energy of the nuclide).

[0091] σ is the peak width, which is related to the energy resolution of the detector.

[0092] S33: Based on the above data processing results, after drawing charts and comparing data, the final third measurement result is obtained.

[0093] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A non-destructive nuclear gamma measurement method based on a NaI detector, characterized in that, include: Without placing the sample to be measured, the NaI detector was placed in a shielded box, and the background signal reference value was measured and recorded. The sample to be measured is placed in the measurement area of ​​the NaI detector, and the first measurement result of the sample is measured and recorded. The second measurement result is obtained by subtracting the baseline from the first measurement result and the baseline signal reference value, using the following formula: in: P smooth (E) is the smoothed spectrum; N is the window size; i is the index in the window; P measured (E)=P signal (E)+P backgruond (AND) in: P measured (E) is the measured total spectrum; P signal (E) is the signal spectrum of the target source; P backgruond (E) is the background spectrum; The second measurement result is processed to obtain the final third measurement result, using the following formula: in: P(E) is the count rate at energy E; A is the peak height, representing the signal strength; E0 is the central energy of the peak; σ is the peak width, which is related to the energy resolution of the NaI detector.

2. The non-destructive gamma measurement method in the nuclear field according to claim 1, characterized in that, Before measuring and recording the first measurement result of the sample, the detection limit and detection time parameters of the NaI detector are calculated, and the NaI detector is set according to the parameters. The calculation formula is as follows: in: L min It is the minimum detection limit; K is a constant that depends on the sensitivity of the detector; B represents background noise; t is the detection time; N signal and N background These are the counts of the signal and the background, respectively.

3. The non-destructive gamma measurement method in the nuclear field according to claim 2, characterized in that, The detection time t is based on the following: 60 The accuracy of the control system for the work shoes of nuclear power plant workers in Co was determined.

4. The non-destructive gamma measurement method in the nuclear field according to claim 3, characterized in that, The control accuracy is such that the measurement reaches 1e-2Bq / g within 2 minutes.

5. The non-destructive gamma measurement method in the nuclear field according to claim 1, characterized in that, The shielding box has a shielding box body, and the side wall of the shielding box body has a through hole. The top of the NaI detector is set as a cylinder, and the cylinder contacts the outside of the shielding box through the through hole.

6. The non-destructive gamma measurement method in the nuclear field according to claim 5, characterized in that, The nuclear electronics section of the NaI detector includes a main amplifier circuit.

7. The non-destructive gamma measurement method in the nuclear field according to claim 6, characterized in that, The main amplifier circuit includes a voltage amplifier, a first connector, and a second connector. The voltage amplifier is equipped with an operational amplifier U19, a feedback resistor R74, and an input resistor R68 for signal amplification. The first connector and the second connector are used to transmit the amplified signal to the outside.

8. The non-destructive gamma measurement method in the nuclear field according to claim 7, characterized in that, The input resistor R68 is connected to the inverting input terminal of the operational amplifier U19, and the non-inverting input terminal of the operational amplifier U19 is grounded.

9. The non-destructive gamma measurement method in the nuclear field according to any one of claims 1-8, characterized in that, The shielding box measures 200mm × 400mm × 75mm.

10. The non-destructive gamma measurement method in the nuclear field according to claim 9, characterized in that, The shielding box is equipped with a lead plate inside, and the lead plate is 4-7mm thick.

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