大地からのγ線に対する雪の遮蔽効果

概要

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The effect of snow cover on the exposure rate from terrestrial gamma radiation was evaluated by a computer simulation based on the Adjoint Monte Carlo Method. Snow was assumed to cover the smooth-flat interface of infinite half space, where uranium and thorium series, and potassium were distributed uniformly. Snow shielding factors were defined as the quotients of the terrestrial gamma exposure rates with snow cover by those without snow cover, and were presented for three variant snow densities as well as for snow cover expressed in the unit of g/cm2. The snow shielding factors have little dependence on radioactive sources: uranium, thorium series or potassium. The present snow shielding factors were, at maximum, about 40% higher than those reported by Sievert and Hultqvist, which have been often cited so far. It was found, however, that their calculation has a mistake of underestimating the contribution of scattered radiation.
日本保健物理学会の論文