Radon removal trap design and coefficient testing for the development of an effective radioxenon sampling, separation and measurement system

摘要

To monitor low-level radioxenon isotopes activity concentrations in the bulk gases, a radioxenon sampling, separation and measurement system has been developed. The xenon enrichment factor of this system is more than 105 after the separation of impurities, including N-2, O-2, CO2 and H2O, as well as radon and its progenies, such as Pb-214 and Bi-214. Since radon and its progenies interfere with radioxenon measurement, they have to be removed before radioxenon counting. To separate radon from xenon, different dynamic adsorption coefficients of xenon and radon are used to design small radon removal trap to retain radon after eluting xenon, and the ratio between radon and xenon dynamic adsorption coefficient gives the adsorbent weight relationship between the xenon adsorption trap and its related radon removal trap. To test the effectiveness of radon removal, the relative measuring method is used by measuring gamma-rays energies of radon progenies in canister filling with either the measuring sample prepared by the system or the original gas. The results show that the radon removal coefficient and the stable xenon recovery, which are two important parameters in the radioxenon system, are at the order of 10(-6) and 70% respectively. These meet the specifications proposed by the Comprehensive Nuclear Test-Ban Treaty Organization.