The radioactive gas 85Kr (beta emitter, Emax: 687 keV, half-life: 10.76 years) is derived from anthropogenic sources such as nuclear weapons tests, nuclear-fuel reprocessing and nuclear reactors. The determination of 85Kr in air is carried out owing to two major purposes of the environmental radioactivity monitoring and the detection of nuclear activities of neighboring countries. To measure low-level 85Kr radioactivity in the atmosphere, a Budesamt für Strahlenschutz - Institute of Atmospheric Radioactivity (BfS-IAR) system is the only commercialized system developed by the Budesamt für Strahlenschutz (Germany). However, the system requires a lot of manpower because all stages to get data should be performed manually although reliable data with a high level of accuracy were obtained by using the system. For this reason, automation of the system is significant and should be rapidly carried out to get continuous data without manpower. The analysis system consists of steps of air sampling, first concentration, second concentration, separation/purification and determination of radioactivity. At the sampling step, air including Kr flow into and adsorbed in an adsorption module cooled with liquid N2 after removal of moisture and CO2. In this study, the sampling step was automated by using a membrane module, a heat exchanger, an automatic air-flow distribution system, a thermostat bath and newly designed modules. Our new automated sampling system for a 85Kr analysis was well operated. Used materials and equipments for automated sampling system were analyzed with FT-IR, SEM, GC, etc. In our presentation, we will talk about the analysis results and next plan for the automation of other steps for the 85Kr separation system. In addition, the distribution of temperature in the adsorption module was analyzed with an ANSYS software to design new adsorption modules. Numerical simulations of air flow with various temperatures into the adsorption module was presented. The developed air sampling system was well operated automatically, and demonstrated high sequestration efficiency of moisture and CO2 in the air sample. We expect our study will be a stepping stone to develop the automated 85Kr analysis system for the radioactive noble gas monitoring.

Development of automated air sampling system including CO2 and moisture separation process for analysis of radioactive 85Kr

2019 Spring National Meeting

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