Development of the technique for monitoring 85Kr in environmental air

The analysis of atmospheric 85Kr is needed for accurate concentration data which will become more imperative in order to asses the radiation dose to the population and to predict future trend as the nuclear power industry expands. The apparatus for separation of krypton from air consisting of all metal tube vacuum system with series of cryogenic absorption traps was constructed. One to three cubic meters of air sample is reduced to several milliliter of krypton. A low-background liquid scintillation counter equipped with an anti-coincidence plastic scintillation detector was developed. Rapid and accurate solubilizing method of krypton to toluene or xylene was established. Optimum counting condition for 85Kr measurement in liquid scintillation counting was determined by internal standard method and by absolute measurement techniques. A krypton sample removed from the air at Himeji city in autumn of 1972 was analyzed. The value of 85Kr concentration is 14.0+-0.3 pCi/m3 air which agrees well with foreign data. (auth.)