CN-122017925-A - Self-adaptive purging low background device and method for high-purity germanium gamma spectrometer

CN122017925ACN 122017925 ACN122017925 ACN 122017925ACN-122017925-A

Abstract

The invention discloses a self-adaptive purging low background device and method for a high-purity germanium gamma spectrometer, and relates to the technical field of radionuclide detection. The device comprises an air source module, a flow control module, an inner cover, a purification module, a sensing module and a main control module, wherein the method comprises the steps of S1, starting a self-adaptive purging low background system of the high-purity germanium gamma spectrometer, S2, obtaining monitoring data of the sensing module, S3, judging whether the pressure difference exceeds a pressure difference threshold value, S4, judging whether the humidity or radon gas concentration exceeds a corresponding threshold value, S5, obtaining nitrogen purging flow by using a box model, S6, realizing nitrogen purging flow control by using the flow control module, and S7, ending. According to the invention, on the premise of not changing the high-purity germanium gamma spectrometer body, the self-adaptive regulation and control under the low background condition is realized by introducing a first-order linear box body mass conservation model and dynamically calculating the nitrogen purging flow by utilizing real-time monitoring data by using the existing equipment.

Inventors

WEI XIN
LIU YINGNA
GAO XIAOFEI
LIU BAOYUAN
GONG JIRUI

Assignees

北京师范大学

Dates

Publication Date: 20260512
Application Date: 20260410

Claims (10)

1. The self-adaptive purging low background device for the high-purity germanium gamma spectrometer is characterized by comprising an air source module, a flow control module, an inner cover, a purification module, a sensing module and a main control module, wherein the inner cover is positioned in a lead chamber of the high-purity germanium gamma spectrometer, then the air source module, the flow control module, the inner cover and the purification module are sequentially connected to form an air flow path, the sensing module is positioned in the inner cover and the lead chamber and is used for receiving monitoring data, the main control module is respectively connected with the air source module, the flow control module and the sensing module and is used for receiving the monitoring data or sending control parameters, and the self-adaptive purging low background device is specifically: The air source module is used for enabling the nitrogen to stably enter the inlet of the flow control module according to the pressure value set by the main control module; The flow control module is respectively connected with the air source module, the inner cover and the main control module, and receives nitrogen from the air source module and inputs the nitrogen into the inner cover through an air inlet hole of the lead chamber of the high-purity germanium gamma spectrometer according to the output flow of the nitrogen received from the main control module; The inner cover is a cover arranged in a lead chamber of the high-purity germanium gamma spectrometer, and is made of transparent acrylic material and covers a sample area to form a local closed space; the purifying module is used for removing radon gas in the gas discharged from the vent hole of the lead chamber of the high-purity germanium gamma spectrometer, the inlet of the purifying module is connected with the vent hole of the lead chamber, and the gas is directly discharged into the air after the radon gas is removed; The sensing module is used for measuring the temperature and humidity, the radon gas concentration and the air pressure of the inner cover and the lead chamber, is connected with the main control module and sends monitoring data to the main control module; The main control module is respectively connected with the air source module, the sensing module and the flow control module and is used for receiving monitoring data from the sensing module and controlling the air source module and the flow control module to realize flow regulation by setting equipment parameters.
2. The self-adaptive purging low background device for the high-purity germanium gamma spectrometer according to claim 1, wherein the main control module comprises a control parameter sub-module, a data acquisition sub-module, a threshold judgment sub-module, a flow regulation sub-module and a data storage sub-module, and is specifically: The data acquisition submodule is used for receiving data acquired by all the sensors, and the data acquisition submodule sends the acquired data to the threshold judgment submodule, the flow regulation submodule and the data storage submodule; The threshold judging submodule is used for comparing the set threshold value with a set threshold value, giving out control parameters of corresponding equipment according to a comparison result, and sending the control parameters to the control parameter submodule; The flow regulating sub-module is used for obtaining nitrogen purging flow according to the temperature and humidity value, radon gas concentration, inner cover air pressure and lead chamber air pressure obtained by the data acquisition sub-module, and sending the nitrogen purging flow to the control parameter sub-module as the control parameter of the flow control module; the control parameter submodule is used for sending control parameters to corresponding equipment; the data storage submodule is used for storing corresponding data and parameters to the database according to the setting.
3. The self-adaptive purging low background device for the high-purity germanium gamma spectrometer of claim 1, wherein the sensing module comprises a temperature and humidity sensor, a radon on-line monitor, a first air pressure sensor and a second air pressure sensor, wherein the temperature and humidity sensor is arranged at the upper part of the inner cover and used for monitoring the temperature and humidity in the inner cover, a sampling port of the radon on-line monitor is arranged near an exhaust hole at the top of the inner cover and used for monitoring the concentration of radon gas in the inner cover, the second air pressure sensor is arranged in the inner cover and used for monitoring the air pressure of the inner cover, and the first air pressure sensor is arranged in a lead chamber and used for monitoring the air pressure in the lead chamber.
4. The self-adaptive purge low background device for a high purity germanium gamma spectrometer according to claim 2, wherein the main control module further comprises a linkage scheduling sub-module; the linkage scheduling sub-module automatically generates a background spectrum measurement task after triggering a daily or weekly background spectrum measurement plan, sends control parameters to the control parameter sub-module and the data storage sub-module according to the background spectrum measurement task, starts a purging or monitoring task, and generates an operation log.
5. The method for using the self-adaptive purging low background device for the high-purity germanium gamma spectrometer according to claim 1, which is characterized by comprising the following steps: s1, starting a self-adaptive purging low background device for a high-purity germanium gamma spectrometer; s2, acquiring monitoring data of a sensing module; acquiring temperature, humidity, radon gas concentration, inner cover air pressure and lead chamber air pressure which are obtained by monitoring by a sensing module; S3, judging whether the pressure difference exceeds a pressure difference threshold value; When the air pressure difference between the inner cover and the lead chamber is smaller than the air pressure difference threshold value, short-time current increasing is carried out for a preset time length to ensure that a positive pressure environment is maintained, and when the air pressure difference between the inner cover and the lead chamber exceeds or is equal to the air pressure difference threshold value, S4 is directly executed; S4, judging whether the humidity or radon concentration exceeds a corresponding threshold value; when the humidity or the radon gas concentration exceeds the corresponding threshold value, executing S5, and adjusting the nitrogen purging flow; s5, obtaining nitrogen purging flow by using a box model; s51, obtaining by using radon gas concentration box model A first minimum steady-state demand flow at a moment; first minimum steady-state demand flow at time Is calculated according to the formula: (6); wherein: Is that The first minimum steady-state demand flow at the moment is expressed as m 3 /h, Taking the target value of the radon concentration in the inner cover as a radon threshold value; Is that The rate of entry of radon at the moment in time, Is a fitting value of equivalent air exchange rate when radon concentration is not purged, Is the decay constant of radon, Is the effective volume of the inner cover, and is obtained according to the formula (6) First minimum steady-state demand flow at time Namely satisfy Is a minimum nitrogen flow rate; S52, obtaining by using the humidity box model The second minimum steady-state demand flow at the moment; Time second minimum steady-state demand flow The formula of (2) is: (15); wherein: Is that At the moment of time a second minimum steady-state demand flow, Is that Time temperature The actual absolute humidity target value in the lower inner cover, Is that The rate of entry of water vapor at the moment, Fitting values for equivalent ventilation rates when the actual absolute humidity is not purged are obtained according to formula (15) Time second minimum steady-state demand flow Namely satisfy Is a minimum nitrogen flow rate; S53, determining nitrogen purging flow; At the position of Time first minimum steady-state demand flow sum The selected flow rate of the second minimum steady-state demand flow rate at the moment is set as the higher one Moment nitrogen purge flow : S6, realizing nitrogen purging flow control through a flow control module; after the nitrogen purging flow is obtained, the main control module sends the nitrogen purging flow to the flow control module, and then the flow control module outputs nitrogen to the inner cover at the received nitrogen purging flow; And S7, finishing, wherein the main control module records temperature, humidity, pressure difference and radon concentration data according to a preset time interval, stores the data into a database, and when receiving a closing instruction, the main control module closes the nitrogen output of the flow control module to finish the control flow.
6. The method of claim 5, wherein S1, starting the self-adaptive purging low background device for the high-purity germanium gamma spectrometer specifically comprises: after receiving a starting instruction, initializing the self-adaptive purging low background device for the high-purity germanium gamma spectrometer according to received or pre-stored control parameters, detecting communication states among a main control module, a gas source module, a flow control module and a sensing module in the initializing process, reading temperature, humidity, inner cover air pressure and lead chamber air pressure output by the sensing module to judge whether the self-adaptive purging low background device for the high-purity germanium gamma spectrometer is in an allowed running state, prohibiting the main control module from entering a purging process and outputting alarm information when detecting that any module state does not meet preset running conditions, and entering the running state when all parameters meet the running conditions.
7. The method of claim 5, wherein S3, when the air pressure difference between the inner cover and the lead chamber exceeds a specified threshold, the short-time flow increasing is performed for a preset time length to ensure that a positive pressure environment is maintained, and the method is characterized in that: and when the air pressure difference between the inner cover and the lead chamber is smaller than a specified threshold value, short-time flow increase is carried out at a preset flow increase speed within a preset time length, and the flow control module restores the nitrogen purging flow to the nitrogen purging flow before the short-time flow increase after the short-time flow increase is carried out, and returns to S2.
8. The method of claim 5, wherein S51 is a method of using an adaptive purge low background device for a high purity germanium gamma spectrometer The relationship with humidity and air pressure is shown in formula (4): (4); In the formula, Is arranged in the inner cover The relative humidity at the moment in time is, Is arranged in the inner cover The air pressure at the moment in time, For the initial radon entry rate, For the initial relative humidity within the inner housing, For the initial air pressure within the inner housing, As a first parameter of the first set of parameters, For the second parameter, a least squares fit is used to obtain Fitting values of (a) ; In order to achieve natural ventilation strength generated when nitrogen is not blown, the radon attenuation method is utilized, and when nitrogen is not blown, the radon concentration in the inner cover is as follows The decay after the interval time satisfies the following conditions: (5); In the formula, In order for the time interval to be within, For interval time The radon concentration actually measured later; For the radon gas concentration actually measured at the beginning, according to the formula (5) Fitting values of (a) 。
9. The method of using an adaptive purge low background device for a high purity germanium gamma spectrometer of claim 5, wherein: in S52, the relative humidity obtained by the temperature and humidity monitor is Firstly, converting relative humidity into absolute humidity, and specifically: Saturated water vapor pressure adopts a magnus formula: (7); Actual water vapor pressure: (8) ; the conversion formula between the relative humidity conversion and the actual absolute humidity is: (9) ; wherein: for the current temperature monitored by the temperature and humidity sensor, Is the temperature The saturated water vapor pressure at the time of the process, For the relative humidity monitored by the temperature and humidity sensor, For the actual water vapor pressure to be the same, Is the actual absolute humidity; The relationship with temperature and air pressure is shown in formula (13): (13); In the formula, Is the rate of entry of water vapor at the initial moment, Is arranged in the inner cover The temperature at the moment of time is, For the temperature at the initial moment in the inner housing, Is arranged in the inner cover The air pressure at the moment in time, For the initial air pressure within the inner housing, As a third parameter, the first and second parameters, For the fourth parameter, the least square fitting is adopted to obtain Fitting values of (a) ; For equivalent ventilation rates when no purge is performed for actual absolute humidity, Fitting calculation by equation (14): (14); wherein: The absolute humidity of air in the inner cover at the initial moment; Time of day The absolute humidity of air in the inner cover; is the absolute humidity of the ambient air of the lead outdoor laboratory.
10. The method of using an adaptive purge low background device for a high purity germanium gamma spectrometer of claim 5, wherein: also comprises the step of automatic scheduling, The device repeatedly executes S1-S7 in a designated period, records radon concentration and humidity, and uploads the data to a database for long-term analysis to optimize the threshold.

Description

Self-adaptive purging low background device and method for high-purity germanium gamma spectrometer Technical Field The invention relates to the technical field of radionuclide detection, in particular to a self-adaptive purging low background device and method for a high-purity germanium gamma spectrometer. Background Soil erosion and deposition processes are one of the most important landform evolution and environmental processes in the earth surface system, and directly affect the stability of the land ecological system, the utilization of water and soil resources and the sustainable development of human society. How to accurately reconstruct erosion and deposition rate on the scale of centuries is a core problem of environmental science and soil and water conservation research. 210 Pb (half-life 22.3 a) has become an important radioactive tracer for soil erosion and deposition in the near hundred years scale due to its suitable time window, well-defined source mechanism and stable atmospheric settling characteristics as a natural radionuclide in 238 U decay system. 210Pbex The annual method is one of the most mature means in current environmental deposition research. The basic principle is that 210Pbex inputs are continuously obtained from surface sediment, and the activity decays exponentially as the burying time increases. By establishing a distribution of the activity of the deposition profile 210Pbex over depth or cumulative mass, the deposition age and rate can be inverted. 210 The half-life of Pb covers just about hundred years of human activity and climate change scale, providing critical time information between 137 Cs and 14 C. High purity germanium HPGe gamma spectrometers are widely used for analysis of environmental nuclides 210Pb、137 Cs and the like with their excellent energy resolution. However, in practical applications, the low-energy measurement sensitivity of 210 Pb at 46.5keV is extremely susceptible to strong interference and self-absorption by radon 222 Rn and its daughter. Therefore, in order to accurately measure 210 Pb content, a practical method is needed to suppress radon background. In order to reduce radon interference, the common modification method comprises (1) physical sealing, namely adding a plastic film or a metal cover outside the probe to limit air exchange, wherein the sealing effect is limited and is unfavorable for sample replacement. (2) Environmental-level purification, such as whole nitrogen purification of a low-background laboratory and a deep underground laboratory, but has extremely high cost, and is not suitable for popularization of general universities and scientific research institutions. In addition, the humidity of the environment where the instrument is located is an important factor influencing the stability of the instrument, but most of existing systems rely on manual monitoring of the humidity, and the degree of automation is low. The existing high-purity germanium gamma spectrometer basically adopts quantitative nitrogen input, and has the defects of high gas consumption, poor long-term operation economy, lack of dynamic adjustment, inability of flexible control according to actual humidity and radon gas level and the like. Therefore, the prior art has the following defects of lack of real-time monitoring and feedback of humidity, radon concentration and pressure difference, fixed purging flow, incapability of being adjusted according to needs, overlarge nitrogen consumption, incapability of long-term operation, lack of linkage with database scheduling and incapability of intelligent optimization by combining long-term background data. Disclosure of Invention In order to solve the defects in the prior art, the invention aims to provide a self-adaptive purging low-background device and a self-adaptive purging low-background method for a high-purity germanium gamma spectrometer, which realize self-adaptive adjustment of nitrogen purging through multi-sensor fusion and intelligent control, reduce gas consumption and improve the operation efficiency and reliability of a laboratory while keeping a long-term low background. The invention provides a self-adaptive purging low background device for a high-purity germanium gamma spectrometer, which comprises a gas source module, a flow control module, an inner cover, a purification module, a sensing module and a main control module, wherein the inner cover is positioned in a lead chamber of the high-purity germanium gamma spectrometer and then is sequentially connected with the gas source module, the flow control module, the inner cover and the purification module to form a gas flow path, the sensing module is positioned in the inner cover and the lead chamber and is used for receiving monitoring data, the main control module is respectively connected with the gas source module, the flow control module and the sensing module and is used for receiving the monitoring data or sending control parameters, and