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The Hanford Environmental Dose Reconstruction (HEDR) Project is developing environmental transport and dose models to estimate the doses to individuals and populations from exposure to radionuclides released from Hanford nuclear facilities since 1944. The validity of these models will be assessed in part by comparing model predictions with environmental measurements of radionuclides. One potentially important set of environmental radionuclide measurements is those made on vegetation samples that, beginning in 1945, were collected on and around the Hanford Site. However, from October 1945 through mid-1948, the available technology permitted the vegetation samples to be measured only for total radioactivity rather than for specific radionuclides. At that time, the factors needed to convert total radioactivities to concentrations ({mu}Ci/kg) of iodine-131, the predominant radionuclide that was released into the air from Hanford stacks in the mid-1940s, were not well known or accurately quantified. A search of historical Hanford records by HEDR Project staff uncovered the original background-corrected radiation measurements, made using a Geiger-Mueller (GM) detector system, for vegetation samples that were collected from October 1945 through early August 1946. HEDR Project staff have developed a model that can be used to convert these radiation measurements to iodine-131 concentrations ({mu}Ci/kg). It is anticipated that this equation will be used to obtain more accurate concentrations of iodine-131 for vegetation for the purpose of validating vegetation iodine-131 concentrations that will be estimated by HEDR Project air-pathway transport models. |
