Hanford Site Retrospective on Historical Annual Radioactive Air Emissions Doses

Radioactive air emissions are regulated by both the US Environmental Protection Agency (US EPA) and the State of Washington. Both agencies have adopted an annual dose limit of 0.1 mSv y-1 (10 mrem y-1) effective dose equivalent to a maximally exposed individual (MEI) member of the public. Compliance to the US EPA standard is determined by calculating the highest dose from radioactive air emissions due to point source emissions to a member of the public at a residence, school, business or office. Under the Washington State requirements radionuclide emissions and doses to members of the public include not only point sources but also radon and diffuse/fugitive doses. This retrospective review summarizes the annual Hanford Site radionuclide air emissions reports for the past 35 years beginning in calendar year 1990 through 2024, and it compares the results of the federal versus the state reported doses to the MEI. Additional considerations include the dose model version, location of the reported MEI, maximum emission unit contributor to dose, and the percent contribution of the predominate emitted isotopes. The comparison of the results from the two reporting methods shows low doses, in comparison to the limits, to members of the public and that the more expansive state doses are typically 2.4 times more than that of the federal requirement. This variation appears to be independent of the CAP88 dose model used. Finally, the annual radioactive air emissions dose to the MEI from the Hanford Site over the 35-year period to a member of the public is on average about 1% of the 0.1 mSv y-1 state limit.