Research Of Standardization Of²²²Rn/²²⁰Rn Reference Level Determination In²²⁰Rn Chamber

The research of the standard method for metrology of220Rn and its progeny isone fundamental study of metrology technique of thorium utilization project innuclear energy. The standard measuring methods (devices) for metrology of220Rn isthe base of calibration and test for other220Rn measuring methods to guarantee themonitoring quality of220Rn measuring devices which are used for the nationalresearch and production, and field measurement. So the research of thestandardization of determination method of222Rn/220Rn reference levels in220Rnchamber is very necessary.This paper mainly focused on the three parts of research as following:1. The exsiting gas-through and static time-delay method by using singlescintillation cell for measuring222Rn/220Rn concentrations was perfected andoptimized, and the standardization research was carried on. The already establishedmeasuring device for the gas-through and static time-delay method by using singlescintillation cell was simplified, and it makes the experiment device and operationmore simple and convenient. The measuring procedures were optimized by different222Rn/220Rn levels, and it can minimize the error caused by statistical fluctuations. Thereal sampling flow rates were simulated and the error caused by flow rates can becontrolled strictly. Scintillation cells were calibrated and the calibration factors ofscintillation cells for measuring222Rn/220Rn were obtained. Moreover, the specificerror analysis of every measuring elements of the standardization method was carriedon. The determination devices of gas-through and static time-delay method by usingsingle scintillation cell for the reference levels of222Rn/220Rn in the220Rn chambercould meet the requirement of220Rn concentrations being determined in the range of（100-105）Bq·m-3.2. In order to realizing the stable and continuous monitor of222Rn/220Rn concentrations in220Rn chamber, the existing RAD7222Rn/220Rn measuring devicewas improved. The interference of sampling flow rates to220Rn measurement wascalibrated and the question of accurate measurement of220Rn was also resolved. Thecomparison between RAD7and the gas-through and static time-delay method byusing single scintillation cell was carried on. The accuracy and reliability of twomethods are defined and verified each other.3. Operating procedures of the standard methods for metrology of220Rn wereformulated and technical specification of calibration (or graduation) for220Rnmeasuring devices was drafted. It can meet the need of test, calibration and quantitytransmission of the standardization method, and moreover the quality assurancesystem of222Rn/220Rn metrology has taken shape initially.