Research On Radioactive Aerosol Measurement Technology Based On Energy Screening Method

Radioactive aerosol is the main cause of human exposure,which can be divided into natural radioactive background and artificial radioactive aerosol.Transuranic nuclides has a long half-life and is highly toxic,once inhaled,which will damage the health of the workers in the nuclear facilities.Therefore,it is an urgent demand of the rapid and accurate measurement of artificial radioactive aerosols for radiation protection.In this paper,the optimization of the parameters of artificial alpha radioactive aerosol was studied by using the energy discrimination method.We used Canberra iSolo which is designed to measure radioactive aerosols,its performance of radon thorium background compensation was tested,and found that it does not meet the requirements of the rapid measurement as their company preached.Therefore,uses it was just used as a function of alpha spectrometer in this paper.The compensation coefficient K is the key parameter in the energy discrimination method,in this study,the factors affecting the K value were simulated and analyzed.Various kinds of sampling filters were tested,including self-absorption,extraction resistance and filtration efficiency.Finally,PTFE membrane produced by CNNC(China Institute for Radiation Protection)was chosen.The decay law of nuclides on the membrane was calculated,then time dependence of the compensation coefficient K was analyzed.Found out that:the value of K was found to increase with the increase of sampling time;the K value will be significantly reduced while wait for a period of time after the end of the sample;the measurement time is not the longer the better,it's depends on the sampling time.Monte Carlo program MCNPX was used to simulate the effect of the air layer,it is found that the vacuum pumping has a significant improvement in the reduction of the energy spectrum,and it doesn't deed a high degree of vacuum,the pressure of 10KPa will achieve the requirementsUnder the condition of laboratory,the reasonable selection of the sampling filter and the time distribution were carried out.The results show that the detection limit can reach 0.079 Bq/m3,and the error of the measured aerosol activity is less than 20%when using energy discrimination method.The purpose of rapid dose estimation after the completion of the operation is realized.