Research And Design Of In-situ Gamma Spectrometer System In Water Area

Timely and accurate monitoring of radioactive levels in waters is an effective and necessary nuclear safety measure.In-situ gamma spectrometer technology is an emerging online monitoring method for radioactive pollution in waters,which can effectively solve the problems of long sampling period and cumbersome operation in traditional laboratory analysis methods.However,the design of in-situ gamma spectrometer systems in water areas faces a series of problems and challenges.First of all,the background of the water environment is complex,and the superposition of natural nuclides and target nuclides puts forward higher requirements for the energy resolution of the system.Secondly,the content of radionuclides in water is low,so efficient gamma energy spectroscopy measurement methods and high-sensitivity detectors are required.In addition,since the in-situ gamma spectrometer needs to be mounted on a mobile platform such as an autonomous underwater vehicle to achieve rapid mobile monitoring of a large area of water,the stability of the spectrometer system will inevitably be affected by changes in the ambient temperature of the water area.In view of the above problems,this paper uses Monte Carlo simulation,digital peak finding,spectrum stabilization and other technical routes to carry out the research and design of the in-situ gamma spectrometer system in water areas:1)Through Monte Carlo simulation calculations,the detection efficiency,background energy spectrum（including the scintillator’s own radioactivity）,minimum detectable activity concentration and other indicators,and make a comparative analysis.Finally,the gamma spectrometer probe is designed with a new Ce Br₃ detector with high sensitivity and high resolution.The simulation experiment results provide an important theoretical reference for the probe design of the in-situ gamma spectrometer system in water areas.2)The hardware and software design of the in-situ gamma spectrometer system in water areas has been completed.In terms of system hardware,the selection and circuit design of the gamma spectrometer system probe,signal acquisition circuit board,digital multi-channel analysis board and other modules have been mainly completed.In terms of software,the embedded software of the lower computer based on FPGA is designed to realize the functions of data acquisition and reception,signal processing,communication and so on.In addition,the host computer software is designed to realize the functions of spectral line display,data processing and file storage.3)Carried out the research on digital core signal processing algorithm and its realization on FPGA.A pre-denoising algorithm is designed using FIR filter to preserve the original signal shape and remove high-frequency noise;The optimized cascade structure is used to solve the baseline drift problem of the trapezoidal algorithm;A stacked pulse identification algorithm is designed by combining amplitude criterion and width criterion;A dynamic baseline estimation algorithm and a peak extraction algorithm are designed by using the simple average method;And aiming at the real-time problems of traditional spectrum stabilization methods,a spectrum stabilization method based on digital nuclear signal processing is designed.This method adjusts the amplitude of each pulse signal in real time to achieve fast and timely compensation of system gain.Finally,through temperature experiments The feasibility and reliability of this method are verified.4)Based on the above work,a system prototype and an experimental platform were built,and the main performance indicators of the system,such as energy linearity,energy resolution,temperature adaptability and system stability,were tested.Experimental results verify the effectiveness and feasibility of the whole system.The research results of this paper provide specific and feasible technical routes and solutions for related system design,and provide useful reference and reference for research and development in related fields.