CN113921151A

CN113921151A - Containment pressure relief and exhaust activity monitoring signal processing system

Info

Publication number: CN113921151A
Application number: CN202111060598.XA
Authority: CN
Inventors: 马天骥; 徐卫峰
Original assignee: 719th Research Institute of CSIC
Current assignee: 719th Research Institute of CSIC
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2022-01-11

Abstract

The invention relates to the technical field of nuclear radiation detection, and provides a containment pressure relief exhaust activity monitoring signal processing system which comprises 2 detectors, a data processing display unit and a lead shielding body, wherein the 2 detectors work in a differential mode, the main detector outputs gamma rays of gas to be detected and total count of environmental background, the compensation detector outputs the count of the environmental background, and effective measurement signals are output after background subtraction is carried out through a main channel. The invention provides a containment pressure relief exhaust activity monitoring signal processing system based on a high temperature resistant NaI detector and a digital energy spectrum type signal processing unit, which is simple in structure, excellent in technical performance and strong in environmental adaptability.

Description

Containment pressure relief and exhaust activity monitoring signal processing system

Technical Field

The invention relates to the technical field of nuclear radiation detection, in particular to a containment pressure relief and exhaust activity monitoring signal processing system.

Background

When a reactor of a nuclear power station has a serious accident and the reactor core cannot be cooled in time, the pressure in a containment vessel of the reactor can be increased sharply. In order to prevent the accident of damaging the containment vessel due to the excessive pressure in the reactor, the pressure in the reactor needs to be relieved and exhausted so as to reduce the pressure in the reactor. The containment pressure relief exhaust monitoring channel obtains the activity of radioactive gas discharged to the environment from a reactor in the containment pressure relief exhaust process by measuring the activity of gamma radioactive gas discharged in real time, and effective reference is made for environment assessment.

Because the safety shell pressure relief exhaust monitor is started in a serious accident state, the temperature of a pressure relief exhaust pipeline can reach 140 ℃ during working; meanwhile, the environmental background is high.

In conventional detection means, ionization chamber type detectors are commonly used for dose rate monitoring, and the measurement result is measured according to the total charge generated by a radioactive source in sensitive gas, and cannot record single radioactivity events. During activity monitoring, the radiation activity is reversely deduced by recording the number of counts of the radiation in the detector, so that the ionization chamber detector cannot be used for activity measurement; the G-M tube type detector has high sensitivity and large pulse amplitude, is not interfered by an external electromagnetic field, can record pulse events caused by rays in a sensitive area, but does not have nuclide resolution capability; the normal temperature semiconductor detector commonly used for the semiconductor detector has small sensitive volume, is commonly used for beta ray and alpha ray measurement, and is not used for gamma ray measurement because gamma rays (particularly middle and high energy gamma rays) are not easy to deposit energy in the semiconductor detector; the high-purity germanium detector needs to work under low temperature and cannot be used as a field instrument.

The scintillator detector has the characteristics of high equivalent atomic number, high detection efficiency, large sensitive volume, nuclide resolution capability and the like, and is commonly used in the fields of low radioactivity monitoring and low dose rate monitoring. NaI (Tl) is a commonly used scintillator detector, can realize the characteristics of high temperature resistance, high long-term operation stability and the like, and is widely used in laboratory measurement and nuclear power plant radiation monitoring systems. Radiation measurement can be realized at the temperature of 280 ℃ at most, and nuclide resolution and gamma total activity measurement can be realized.

However, due to the high detection efficiency of the NaI scintillator detector, under the background state of a high radiation environment of a serious accident, the NaI detector which is unreasonably designed is extremely easy to saturate and cannot be normally used.

Disclosure of Invention

The invention aims to overcome the technical defects and provide a containment pressure relief exhaust activity monitoring signal processing system which is used for solving the problem of gas activity concentration measurement in a high-temperature and high-radioactivity state.

In order to achieve the purpose, the invention adopts the following technical scheme: a containment pressure relief exhaust activity monitoring signal processing system comprises 2 detectors, a data processing display unit and a lead shielding body, wherein the 2 detectors work in a differential mode, a main detector outputs gamma rays of gas to be detected and an environment background total count, a compensation detector outputs an environment background count, and an effective measurement signal is output after background deduction is carried out through a main channel. The 2 detectors are respectively connected with the 2 data processing units, the 2 data processing units respectively process signals of the 2 detectors, the detector is a NaI detector, the data processing and displaying unit is a nuclear pulse signal processing unit, the lead shielding body is 150mm thick, and a preamplifier of the detector is shielded.

In the technical scheme, the NaI crystal and the photomultiplier selected by the detector are both of the models resistant to the high temperature of 140 ℃, and the detector is provided with a spring at the bottom of the package to offset the influence of the expansion with heat and contraction with cold of the NaI crystal.

In the technical scheme, the preamplifier is 10m away from the pipeline to be tested, so that the electronic device is prevented from being damaged by high temperature. Because the radiation dose of the environment at the position where the measuring detector is arranged is high, a radioactive measurement reading person cannot directly approach to a measuring point to perform sampling measurement. Therefore, the control cabinet and the display reading meter are far away from the measuring pipeline as much as possible. Because the temperature and the radiation dose around the measuring point are high, electronic components such as a chip of the preamplifier are easily influenced by the temperature and the radiation, in order to avoid the influence of the environmental factors, the preamplifier is separated from the detector, and lead with the thickness of 150mm is adopted to shield the preamplifier, so that the influence of the radiation on a working chip is reduced.

In the technical scheme, the preamplifier of the detector adopts a charge sensitive preamplifier with stable output, larger conversion gain, high counting efficiency and good stability. The signal is transmitted from the photomultiplier to the preamplifier through the coaxial cable, the current pulse signal is coupled and integrated to convert the current pulse into a voltage signal, and the signal after the first stage of amplification is amplified through the second stage of voltage amplification to amplify the signal generated by the 200keV gamma photon to be above the threshold value of the main amplification. In order to reduce the attenuation in the signal transmission process, a transmitting follower is arranged behind the second stage amplification section of the preamplifier so as to improve the driving capability of the preamplifier on the signal. An 8065 chip with a large pulse width is used as a follower, so that the noise interference of a long cable is not easy to occur during transmission, and the test transmission distance can reach over 80 m.

In the above technical solution, the data processing and displaying unit provides the following functions: the system has the functions of detector coupling, data processing, energy spectrum analysis, measured value display, acousto-optic indication, touch screen control query, remote transmission interface, fault detection and the like.

The invention provides a containment pressure relief exhaust activity monitoring signal processing system based on a high-temperature resistant NaI detector and a digital energy spectrum type signal processing unit, which has the advantages of simple structure, excellent technical performance and strong environmental adaptability, and can effectively solve the problem of monitoring the concentration of gas activity in a high-temperature and high-radioactivity environment in an accident state.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention.

FIG. 2 is a schematic diagram of the signal transmission of the measurement probe of the present invention.

Fig. 3 is a schematic structural diagram of the detector of the present invention.

FIG. 4 is a block diagram of a data processing display unit according to the present invention.

Wherein: 1. the device comprises a measuring detector, 2 a compensation detector, 3 a measuring data processing and displaying unit, 4 a compensation data processing and displaying unit, 5 a lead shielding body, 6 a NaI crystal (Tl), 7 a PMT photomultiplier, 8 a preamplifier, 9 a main amplifier, 10 a NaI crystal, 11 a photomultiplier, 12 a spring, 13 a display module, 14 a measuring module, 15 an energy spectrum processing module and 16 a power supply module.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Fig. 1 shows an embodiment of the system of the present invention.

The NaI scintillator measurement detector 1 is arranged in a lead shielding body 5, and the activity of pressure relief gas in a pipeline is monitored through a collimation measurement hole which is over against a measurement pipeline. Meanwhile, another identical NaI scintillator compensation detector 2 is arranged in the lead shielding body 5 to perform compensation measurement on the environmental radioactivity. The measurement data processing and displaying unit 3 processes the nuclear pulse signal from the measurement probe 1; the compensation data processing display unit 4 processes the nuclear pulse signal from the compensation detector 2. The measurement data processing and displaying unit 3 acquires the measurement data of the compensation data processing and displaying unit 4, and outputs an effective measurement signal after background subtraction is carried out in a differential mode.

Fig. 2 shows an embodiment of the present invention for measuring the signal transmission of a detector.

The preamplifier 8 adopts an external design for components, so that the preamplifier 8 is 10m away from the position of the pipeline to be detected where the detection element NaI crystal (Tl)6 and the PMT photomultiplier 7 are positioned, and the electronic device is prevented from being damaged under the high-temperature condition.

Because the radiation dose of the environment where the detecting elements NaI crystal (Tl)6, the PMT photomultiplier tube 7 and the preamplifier 8 are arranged is high, a radioactive measurement reading person cannot directly approach a measuring point to perform sampling measurement. Therefore, the control cabinet and the display reading meter are far away from the measuring pipeline as much as possible. In order to avoid signal attenuation and noise distortion through a long-distance cable, a two-stage amplification structure is adopted. The distance between the preamplifier 8 and the main amplifier 9 is 80 m.

The preamplifier 8 adopts a charge sensitive preamplifier with stable output, larger conversion gain, high counting efficiency and good stability. The signal is transmitted from the photoelectric booster tube to the preamplifier 8 through the coaxial cable, the current pulse signal is coupled and integrated to convert the current pulse into a voltage signal, and the signal amplified by the first stage is amplified by the second stage voltage to amplify the signal generated by the 200keV gamma photon to be above the threshold of the main amplifier 9. In order to reduce the attenuation in the signal transmission process, a radiation level follower is adopted after the second stage amplification section of the preamplifier 8 to improve the driving capability of the preamplifier on the signal. An 8065 chip with a large pulse width is used as a follower, so that the noise interference of a cable is not easy to generate during transmission, and the transmission distance can reach more than 80 m.

Fig. 3 shows an embodiment of the detector structure according to the present invention.

The NaI crystal 10 and the photomultiplier 11 selected by the detector are both of the type which can resist the high temperature of 140 ℃. The bottom of the package is provided with a spring 12 which counteracts the effects of expansion and contraction of the NaI crystal 10.

Fig. 4 shows an embodiment of the data processing and displaying unit according to the present invention.

The data processing and displaying unit comprises a display module 13, a measuring module 14, an energy spectrum processing module 15 and a power supply module 16.

The main functions realized by the display module 13 include internal communication, analog input, data storage, acousto-optic control and failure alarm, display control, external communication, real-time clock and the like; the main functions realized by the measurement module 14 include internal communication, measurement and judgment, analog quantity output, alarm output and the like; the main functions of the energy spectrum processing module 15 include internal communication, spectrum processing and the like; the main functions implemented by the power module 16 are internal communication, high voltage generation and control, analog voltage sampling conversion, digital voltage sampling conversion, and the like.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.

The above examples only show one embodiment of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The utility model provides a containment release exhaust activity monitoring signal processing system, includes detector, data processing display element, lead shield, characterized by: the detector comprises 2 detectors, wherein the 2 detectors work in a differential mode, a main detector outputs gamma rays of gas to be detected and total count of environmental background, a compensation detector outputs the count of the environmental background, the 2 detectors are respectively connected with 2 data processing units, the 2 data processing units respectively process signals of the 2 detectors, the detector is a NaI detector, the data processing and displaying unit is a nuclear pulse signal processing unit, a lead shielding body is 150mm thick, and a preamplifier of the detector is shielded.

2. The containment pressure relief vent activity monitoring signal processing system of claim 1, wherein: the NaI crystal and the photomultiplier of the detector are both of 140 ℃ high temperature resistant types, and the detector is provided with a spring at the bottom of the package.

3. The containment pressure relief vent activity monitoring signal processing system of claim 1, wherein: the preamplifier of the detector adopts a charge sensitive preamplifier, and the preamplifier comprises a secondary amplifier; an emitter follower is added behind a preamplifier to improve the driving capability of the circuit, and the preamplifier is far from the pipeline to be tested by 10 m.