Methodologies for calculating the radiation dose to man from environmental releases of tritium

Numerous methods have been recommended for calculating the radiation dose to man from releases of tritium to the environment by nuclear facilities. This study analyzes four different methodologies that vary considerably in modeling detail. The first approach considered is a direct specific activity calculation, which assumes that the concentration of hydrogen in tissue is identical to that in atmospheric water vapor. Other methods considered are those recommended by the National Council on Radiation Protection and Measurements (NCRP), the computer program AIRDOS-EPA sponsored by the Environmental Protection Agency, and the Nuclear Regulatory Commission. With each model, doses are calculated using identical input data so that the resulting dose estimates can be compared. Our analysis leads to the conclusion that the incorporation of certain site-specific data is important in tritium dose models. Increased complexity of models alone, however, does not necessarily result in a more accurate estimate of dose. A compromise between model realism and simplicity is proposed with a modified NCRP methodology outlined in this article. This study might serve as a guide for evaluating other models for assessing radionuclde releases to the environment. It is possible that simpler approaches will still respond to the information needs, such as the specific activity calculation reviewed here, would be adequate for estimating dose from radioactive discharges