Thermoluminescent dosimeter (CaF2:Dy) measurement of the Hanford environs, 1971--1975

The average external dose rate measured at locations in the Hanford environs was 72 mrad/year, based on analysis of thermoluminescent dosimeter data collected from 1971 through 1975. The maximum dose observed, 84 mrad/year, occurred approximately 100 feet north of the Vernita rest stop on Hanford Site property. This location is free of pedestrian or vehicular traffic and the increased dose is attributed to the greater abundance of naturally occurring radionuclides, primarily 40K, at this location. The lowest dose measured, 62 mrad/year, occurred at Sunnyside. The dosimeter at this location is affixed to a wooden building and the shielding provided by the building is expected to account for the lower observed dose. The average dose received from naturally occurring radioactivity in the Hanford environs was estimated from the external dose measured by the thermoluminescent dosimeters and from information available in the literature. Terrestrial and cosmic ionizing radiation each contribute approximately 36 mrad/year. The neutron component of cosmic radiation contributes an additional 0.8 mrad/year or, utilizing a quality factor of 8, a dose equivalent of about 6 mrem/year. The combination of the terrestrial and cosmic ionizing doses and the neutron dose yields an overall estimate of 78 mrem/year due to external radiation. The dose received from internally deposited radionuclides was estimated from the literature to be 25 mrem/year. Therefore, the total radiation dose received from natural causes was estimated to be 103 mrem/year. For convenience, as estimate of 100 mrem/year is suggested