Research On ? Artificial Radioactive Aerosol Monitor In High Radon Environment

With the widespread use of artificial radioactive nuclide,the demand in monitoring artificial radioactive aerosol is increasing.High radon is along with the actual monitoring environment in most cases,especially in underground tunnel and nuclear facilities,it will seriously interfere results when monitoring the concentration of artificial radioactive aerosol.So the difficulty is taking out radon background,accurately and fleetly calculating concentration of artificial radioactive aerosol.it is of great significance and value to reserch on ? Artificial radioactive aerosol monitor in high radon environment.Aimed at monitoring Artificial radioactive aerosol monitor in high radon environment,we design dual channel measurement system and make reserch on nuclear signal acquisition circuit,the selection of sampling filter,measurement of vacuum,deduction algorithm of radon in each channel.The main research results of the paper:?1?Analynzing some measures of monitoring the concentration of artificial radioactive aerosol.Aimed at the demand of time and accuracy of the system,we choose dual channel measurement system to monitor artificial radioactive aerosol.?2?Based on the characteristics of monitoring the concentration of artificial radioactive aerosol,selecting the ULTRA-AS PIPS detector by ORTEC,designing charge sensitive preamplifier and power module.The SNR of preamplifier is about 10,which meets demand of the system.?3?Discussing on the time of dual channel measurement system and make a derivation in selecting sampling time,standing time and measuring time to give consideration of time response and ? spectrum.The sampling time is 30 minutes,standing time is 0,and the measuring time is 30 minutes.?4?Making a study on the influence to ? spectrum by barometric pressure.The research shows that:when the pressure decreasing from 110 Kpa to 10 Kpa,FWHM is decreased clearly;when pressure decreasing from 10 Kpa to 5Kpa,FWHM is hardly decreased.The attenuation to ? particle by air is not playing a decisive role.?5?Making a study on ? spectrum by sampling filter.The results show that in order to reduce the impact from peak tailing,we should use the filters' pore size as same as the size of biggest natural radioactive aerosols?0.5 ?m?,when high-flow system is applied,the filters' pore size are expected to reduce?0.3 ?m?.Hybrid fiber are better than PTFE filters and PES in reducing peak tailing with same pore size?0.45?m?.?6?Making a study on data-processing in two channels.Such as spectrum smoothing,peak searching and deduction arithmetic.In sampling channel,Radon background is deducted by fitting function;In vacuum channel Radon background is deducted by fixed fraction method.The test shows:in 500Bq/m3 radon environment,the theoretical minimum detectable limit of uranium is 1.92×10-3,the theoretical minimum detectable limit of plutonium is 3.35×10-4;in 5000Bq/m3 radon environment,the theoretical minimum detectable limit of uranium is 1.95×10-3,the theoretical minimum detectable limit of plutonium is 4.84×10^-4.