Detailed evaluation of natural gamma-radiation field due to uranium (238U) series.

概要

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Peak counting rates of a Ge (Li) detector for γ-rays of interest and exposure rates at 1 m above the ground have been calculated using the soil and air concentration profiles of naturally occurring radionuclides at Tsukuba (Yatabe City, Tsukuba District, Ibaraki Prefecture). Decrease in the peak counting rate for 609 keV 214Bi γ-ray above the ground, which was due to diffusion loss of 222Rn under the ground, was evaluated to be about 44% of the peak counting rate calculated assuming uniform distribution of 222Rn under the ground, and decrease in the exposure rate was evaluated to be about 13% of the total exposure rate calculated assuming uniform distribution. Field measurement of i-rays from sources in the soil and air was also made with the Ge (Li) detector at Tsukuba. The calculated peak counting rates where the diffusion loss of 222Rn was involved agreed with those observed in situ. During the observation the calculated peak counting rate for the 609 keV γ-ray from airborne 214Bi ranged 319% of that from uniformly distributed 214Bi source under ground, and the calculated exposure rate from the airborne 222Rn daughters ranged 19% of the total exposure rate.
一般社団法人日本原子力学会の論文