<SESSION>ATMOSPHERIC TRITIUM IN THREE DIFFERENT CHEMICAL FORMS IN FUKUOKA

概要

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A portable tritium samploing system was developed for the stepwise collections of tritiated water vapor (HTO), tritiated hydrogen (HT) and tritiated hydrocarbons (CH_3T) in the atmosphere. According to the system, the collection efficiencies of HTO, HT and CH_3T were all estimated to be nearly 100%. Tritium concentrations of HTO, HT and CH_3T in the atmosphere in Fukuoka were measured from 1984 to the present. Atmospheric HTO concentration varies within range from 0.15 to 1.64 pCi/m^3-air or from 22 to 86 pCi/1-H_2O. HTO concentrations expressed in pCi/m^3 show the trend that they are higher in summer and lower in winter. This trend is similar to the variation of atmospheric absolute humidity expressed in g/m^3-air. On the other hand, HT and CH_3T concentrations generally show no seasonal variations with the almost constant values of 0.78-1.90 pCi/m^3 and 0.21-0.86 pCi/m^3,respectively. Annual averaged concentrations of atmospheric tritium expressed in pCi/m^3 are about 0.55,1.14 and 0.38 for HTO, HT and CH_3T, respectively. On the other hand, the specific activities written in tritium unit (TU) are about 16,10^6 and 4x10^4 for HTO, HT and CH_3T, respectively. These facts obviously indicate that not only HTO but also HT should be considered to estimate the radiation effect of tritium ot human being, and that the origins of tritium involved in these species are quite different.
核融合科学研究所の論文