Study On Energy Discrimination Method In Artificial α Radioactive Aerosol Monitoring

The production and operation of nuclear industry system may lead to Uranium,Plutonium and fission products diffusing into air and forming radioactive aerosol.Uranium, Plutonium and other toxic radionuclide with long half-time period are mainlyalpha-emitting radioisotopes, once inhaled, they will do serious harm to human health.Therefore, monitoring artificial α radioactive aerosol is a significant part of radiationprotection in nuclear industry workplace.This paper focuses on study of energy discrimination method of artificial αradioactive aerosol monitoring. It is the fluctuation and accuracy of compensationcoefficient K that strongly influence the performance of monitoring device. In this paper,the factors influencing compensation coefficient K are discussed, and the modificationof compensation coefficient K and fast measurement of thorium daughters α radioactiveaerosol are also raised. In addition, this article establishes the relationships betweenminimum detectable limit and compensation coefficient K, filter paper absorptioncoefficient, detection efficiency, sample flow, measurement time and the concentrationof natural radon daughters α radioactive aerosol. Moreover, a circuit system, includingsemiconductor detector circuit, charge sensitive amplifier, main amplifier as well as thequick data acquisition and processing system which is completely composed ofhardware, is designed based on energy discrimination method, which can measureartificial α radioactive aerosol rapidly through the collection and analysis of pulse signalgenerated by incoming particle.Verified by experiments under laboratory conditions, the experiment results of fastthorium daughters α aerosol measurement are correspond to theoretical results, and thetheoretical derivation about the factors affecting minimum detectable limit is proved tobe valid, both of which can provide basis of theory and practice for optimizing design ofradioactive aerosol monitor. When the circuit system is applied to the radioactiveaerosol monitoring devices, the minimum concentration that can be detected by thisdevice is0.0819Bq/m~3(sample measurement for30min.), which is lower than derivedair concentration of plutonium aerosol(DAC=0.2Bq/m~3). Therefore, the device can timely show whether the concentration of aerosol in the workplace exceeds limit, so asto realize the rapid detection under accident situation.