Research On ? Radiation Monitoring Instrument For Gaseous Radioactive Waste Processing System

There has a huge amount of radioactive exhaust gas during nuclear power plant and spent fuel reprocessing plant operating. As usually, this radioactive gas is collected and processed by Waste Gas Processing System before emissions into the atmosphere. In order to protect environment and people, it is necessary to build an online monitoring instrument for the system controlling which can provide the information about radioactive gas emission.However, nowadays none of monitoring instrument for this system existed in large of pressurized water reactor nuclear power plants. These are not any widely-used monitoring devices used for this system although AP1000 nuclear power technology requesting radioactive measurement to this system.According to the radioactivity monitoring requirements for exhaust air with the hydrogen waste gas from the waste gas processing system of the nuclear power plant, a kind of on-line monitoring project is designed to efficiently solve the problem about radiation monitoring of 85Kr and 133Xe in waste gas containing hydrogen. The detection efficiency and the influences of the environmental gamma background for the monitor have been calculated by Geant4 Monte Carlo soft kit. Thereby, important theoretical references and basis are provided for the equipment development and production. The calculation results show that plastic scintillator with the size of ?20×0.5mm which is based on the on-line monitoring system satisfied the radioactivity monitoring requirements for exhaust air with the hydrogen waste gas from the waste gas processing system of AP1000 nuclear power plant. If the gamma environmental background is smaller than 10?Gy/h, the lead shielding is not needed to add. Two High-speed op-amp(THS4631) was used in the pre-amplifier of this radiation monitor. Noise level and pulse amplitude can meet the requirement for measurement energy range from 50keV to 3MeV and LED self checking instrument was added. Eventually, monitor instrument calibration factor was measured by experimented. The result between MC simulation and experiment result is less than 5%.