Dose-rate coefficients for external exposure to radionuclides uniformly distributed in soil to an infinite depth

Satoh, Daiki   ; Petoussi-Henss, N.*

Dose-rate coefficients, which convert the radioactivity concentration of a radionuclide into an external dose rate, are extremely important in dose assessment for radionuclides in the environment. The International Commission on Radiological Protection (ICRP) has developed and published dose-rate coefficients for 1252 nuclides of 97 elements distributed at various depths in soil. However, the ICRP data are not applicable to dose assessment in reclaimed soils containing naturally occurring radioactive materials (NORMs), which are a problem for long-term exposure of the public, because the dose contributions of series of nuclides produced by radioactive decay are not included and volume sources uniformly distributed in the soil are not addressed. In this study, the dose-rate coefficients have been newly developed for nuclides uniformly distributed to an effective infinite depth in soil based on the ICRP data and methods. In addition, the data were provided for thorium- and uranium-series nuclides in the NORM. The results were compared with those obtained for several nuclides in previous studies and found to agree within about 10%. From the results, we concluded that a systematic data set for uniform-volume sources was properly established.