Modelling of constant and realistic chronic intake scenarios and their implications.

Chronic inhalation intake of radionuclides is possible for radiation workers in the nuclear industry. The International Commission on Radiological Protection (ICRP) provides organ retention fractions as well as daily urinary and fecal excretion for chronic intake of various radionuclides. In this study, organ retention fractions and daily urinary excretion for chronic intake were estimated for constant chronic intake (CCI) and realistic chronic intake (RCI) scenarios. CCI is a daily intake of 1 Bq, and RCI is an intake of 1.4 Bq for five working days followed by two days gap. Radiologically important radionuclides such as 239Pu, 60Co, 137Cs, 131I, and 3H having long, moderate, and short effective half-lives in the deposited organ or whole body were considered. The retention fractions and daily urinary excretion of all the radionuclides studied for RCI were found to converge with those for the CCI scenario at ~40 to 200 days except for daily urinary excretion of 131I.