Research On The Method Of High Accuracy Metrogy Value Transfer Of Radon Concentration

Radon is currently the only natural radioactive inert gas in nature,The impact of radon and its progeny on people has attracted more and more attention,its related research involves radon pollution,environmental science tracking,medical care,radiation protection monitoring and other fields,and related research in these fields must be based on accurate and reliable radon measurement,in order to ensure the accuracy and reliability of the measurement results,the relevant radon measurement instruments used in the measurement process need to be regularly subjected to metrological verification,calibration or testing,the value of the unit of measurement reproduced by the national standard is transmitted to the work measuring instrument by the measurement standards of various levels by means of metrogy value transmission to ensure the accuracy and consistency of the measured object’s value.The source of the relevant radon measurement value is the radon activity standard,and its level of uncertainty will directly affect the accuracy of subsequent metrogy value transfer.Based on the condensate radon absolute measurement device established by the China Institute of Metrology（NIM）,this paper studies the principle and method of preparing a high-accuracy standard radon source,and prepares a standard radon gas source that can be used for the metrogy value transfer of radon acticity with an expanded uncertainty of 0.8%（k=2）;established a supporting standard device for the measurement of radon volume activity,and the process of metrogy value transferring radon volume activity based on radon absolute measurement device and radon volume activity measurement value transmission standard device was improved.Measured the environmental background value in the vacuum sealed chamber,and the inherent background value after filling with high purity nitrogen;the effective volume transmission of the vacuum-sealed cabin was accurately traced,the expanded uncertainty of its effective volume is 0.46%（k=2）,and the reference value of radon volume activity in the cabin was obtained based on the basic principle of calculating the standard radon volume activity;the reference instrument used in the general radon standard device（standard radon chamber）was verified and calibrated with high accuracy,and repeated experiments and linear research experiments on the calibrated instruments are performed at different concentrations,ensuring the metrogy value of the standard radon gas source can be reliably transmitted to the radon measuring instrument;due to differences in altitudes across China,there will be a certain pressure difference,in order to be able to measure radon volume activity more accurately,it is necessary to consider the effect of pressure effects on different types of radon measurement instruments,therefore,different types of radon measuring instruments are calibrated at different pressure points by adjusting the pressure in the cabin;on this basis,the development of a multi-purpose vacuum-sealed cabin with controllable environmental parameters was carried out,sort out related operating procedures and test the basic performance of the cabin,in the early stage,it is mainly used for high-accuracy transmission of radon volume activity metrogy value,later on the basis of this,it can be used for the calibration technology research of ²²⁰Rn,²²²Rn,⁸⁵Kr,³H and other gas nuclides.