Research On Absolute Measurement Method Of Radon Progeny Concentration Based On Triple Coincidence Liquid Scintillation Counter

Radon progeny is one of the key parameters in the radiation dose evaluation in the field of radiation protection.This research aims at the accurate measurement of the four short-lived radon progeny nuclides of ²¹⁸Po,²¹⁴Pb,²¹⁴Bi and ²¹⁴Po in the radon chamber during the verification or calibration of the radon progeny measurement instrument.The radon progeny concentration based on the liquid scintillation triple coincidence device has been studied.In this study,based on the nuclide decay law and the filter sampling method of radon progeny,the mathematical model and formula for absolute measurement of radon progeny based on the liquid scintillation triple coincidence method were deduced,and the calculation software was written to calculate radon progeny concentration.Based on the triple coincidence measurement principle,the triple coincidence measurement device was developed,and the triple coincidence software was compiled,which realized the signal acquisition,data truncation,offline analysis of radon progeny liquid scintillation samples.Subsequently,using the developed liquid scintillation triple coincidence device,the experiments of the radon progeny filter membrane sampling,the liquid scintillation source preparation of the dissolved filter membrane,the radon progeny detection efficiency verification,the segmented calculation of the radon progeny concentration and the Monte Carlo uncertainty evaluation were carried out.The experimental results show that:?1?The detection efficiencies of ²¹⁸Po,²¹⁴Pb,²¹⁴Bi and ²¹⁴Po in the triple coincidence liquid scintillation counter were determined to be 100%,97.55%,99.35%and 100%respectively.?2?The live time correction method is more suitable for the dead time correction of the short half-life mixed nuclides measurement process.If the total measurement time should not be less than 1800 seconds and the number of segments is not less than 3 segments,a variety of segmentation methods can obtain consistent results.?3?The relative uncertainty of the typical measurement result of the radon progeny equilibrium equivalent radon concentration in radon chamber based on the Monte Carlo method is 1.6%.?4?The absolute measurement method of radon progeny concentration established in this study was compared with Thomas-three-segments method,Lavia-three-segments method,nine-segments method,?/?energy spectrum method,LSC-three-segments method and Kerr method.The consistency of the comparison results is judged by the chi-square test,and the calculated chi-square value is less than 1,indicating that the comparison results are consistent within the uncertainty range,and the methods are equivalent.This research has achieved three innovative results:?1?Established an absolute measurement method of radon progeny concentration based on the liquid scintillation triple coincidence measurement technology.?2?The off-line data processing method is studied,and the influencing factors such as the total measurement time,the segment duration and the number of segments in the multi-segment measurement method are studied,and the multi-segment measurement method for the concentration of radon progeny with triple coincidence liquid scintillation counter was established.?3?The Monte Carlo method is applied to the uncertainty evaluation of the radon progeny concentration measurement results,and solves the uncertainty transfer calculation problem of the non-analytical model.This study provides a foundation for improving the accuracy of radon progeny concentration measurement standard.