The Design Of Gas Tritium Measurement System And The Research On The Related Factor

Tritium is a radionuclide with much more migration property. It has been an important strategic material during the development in nuclear industry. With benefiting human society development, various kinds of tritium are released to surface or air in the form of gas, liquid and solid. To ensure the safety of the staff working in the tritium environment and the resident near the nuclear device, it is necessary to test tritium samples in environment of nuclear devices, nuclear power plant, etc.Since1934, people recognized and had a research on tritium when obtained the fact proved the existence of tritium. From1940s, people carried on large-scale tritium production, the related engineering technique on tritium became popular. Some domestic nuclear units has been tracking the advanced technology in foreign countries to do our own research. The radiation protection technology aimed at tritium has been developing and improving. Basic standard in Ionizing Radiation Protection and Safety of Radiation Sources published by The National Standards of China mentioned tritium as low radionuclide, however, it does not mean the protection of tritium is easy. Because of its diffusivity, it is a challenge job on tritium’s radiation protection. Compared to detecting instruments and methods in foreign countries, the studies referred to the area of gas tritium measurement was deficient in domestic cities, also it lacks authoritative basic theories study and technical support, so we are in badly need of an effective instrument or method to measure tritium in the environment.The tritium’s characters like radiation, liquidity and specific storage system determine the difficulty of its collecting and measuring. To solve this problem, with the support of the project HB-01Gas Tritium Concentration Pollution Measuring Instrument teamed up by Chinese Academy of Engineering Physics and Chengdu University of Technology, the thesis analyzed the gas tritium radiation mechanization in the environment, optimally designed the gas tritium concentration measurement, and had a study on basic experiment to find out the best condition and measuring ability. At the same time, it had a serious study on the important factors. In the end, the characteristic equation between tritium concentration and the measurement count rate has been established in the base of proportional counter. It has provided basic data for domestic gas tritium measurement methods research. This thesis mainly completed the following several aspects.(1) The optimization design of gas tritium measuring systemThe detector is proportional counter which was made independently. The matched vacuum system does not only evacuate the detector, but also clean the detector after using. Built-out port can connect to P10cylinder, vacuum pump, the air, the clean gas cylinder(Ar). In order to reduce the circuit noise, optimize the pre-amplifier, simplify the multi-channel pulse amplitude analysis and the power. To show current measuring result and spectral features intuitively, independent developed tritium measuring software can be used to analyze the data, the combination of OLED and keys in the NIM plugin panel can also be used to do rough measurement.(2) Performance test of gas tritium measuring systemThe sample gas is the real gas tritium sample.200mL proportional counter is used to test the performance of the system. The thesis do the experiments about the stability, reproducibility, measuring time, the plateau curve, the background, detection efficiency and the detection limit. In the end the thesis analyzed and summarized the best measuring conditions and performance index.(3) The key parameters test of gas tritium measuring systemBecause of influence from the test system, sample gas and other factors, during the experiment process, there is a certain deviation between the actual measurement value and the theoretical value. On analyzing a single parameter’s influence, use reasonable mathematical fitting method, establish the characteristic equations about different detection efficiency, detectors in different specifications, different concentrations of samples under the some conditions.This thesis’s innovation points are the following three points:1) It is short of technology and methods in the area of gas tritium measurement in domestic country. The thesis designed a gas tritium concentration measurement system suitable for environmental monitoring.2) Do a lot of basic experiments using gas tritium samples. The thesis used the real results to verify the ability of the system and its best measuring conditions.3) Get several influencing factors, and establish the mathematical characteristic equations.The thesis started from the basic characteristic of the tritium, had a study on the basic theory of gas detectors detecting tritium, designed the gas tritium concentration measurement system. The thesis used gas tritium samples with known activity to do performance test. At the same time, do the character experiments for several influence factors, get a lot of valuable data. In the end, draw a equation between sample’s concentration and measurement count rate. The thesis provided an effective method for gas tritium concentration monitoring in the fields of our country’s decommissioning nuclear facilities, environmental monitoring, etc.