Update of K-40 and Ra-226 and Th-232 series gamma-to-dose conversion factors for soil

摘要

Over the last four decades, the dose conversion factors used to calculate external exposure to gamma radiation from soil from K-40 and the Ra-226 and Th-232 chains have been 0.62, 0.042 and 0.46 (nGy/h per Bq/kg), respectively. This work updates these gamma-to-dose conversion factors, taking into consideration the composition, depth and radius of the soil source, and importantly, updated branching ratios, with MCNPX simulations. The new conversion factors are 0.036, 0.357 and 0.482 (nGy/h per Bq/kg) for K-40 and the Ra-226 and Th-232 chains, respectively. (C) 2014 Elsevier Ltd. All rights reserved.