Abstract
Abstract. Eight sites in the Fukushima contaminated area were
surveyed for long-term changes in D-shuttle dose equivalent rate above the
soil surface during 2015–2017. D-shuttle readings in most cases decreased
faster than if due to radioactive decay only. More rapid decrease can be
explained by natural attenuation processes, such as erosion of the topsoil,
the vertical migration of radionuclides in the soil and the deposition of
cleaner sediments transported by surface runoff. According to the time
dependencies of D-shuttle dose rate readings integral rate constants of the
natural attenuation were estimated using the exponential trend-line.
Estimated rate constants of natural attenuation ranged from 7.3×10-3 to 0.48 yr−1, while the correspondent a
half-dose rate decrease was 1.4–95 years.
Funder
Japan Society for the Promotion of Science
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