OVERVIEW OF THE FERNALD DOSIMETRY RECONSTRUCTION PROJECT AND SOURCE-TERM ESTIMATES FOR 1951-1988

The Feed Materials Production Center, northwest of Cincinnati, process ed uranium concentrates and uranium compounds recycled from other stag es of nuclear weapons production, as well as some uranium ore and thor ium. Particulate releases were primarily uranium (natural, depleted, a nd slightly enriched). In addition, two large silos containing radium- bearing residues were emission sources of radon and its decay products . The Fernald Dosimetry Reconstruction Project was undertaken to help the Centers for Disease Control and Prevention to evaluate the impact of the Feed Materials Production Center on the public from radionuclid es released to the environment from 1951 through 1988. At this point i n the study, the project has estimated the quantities of radioactive m aterials released to air, surface water, and in groundwater; developed the methodology to describe the environmental transport of the materi als; developed mathematical models to calculate the resulting radiatio n doses; and evaluated environmental monitoring data to verify that th e estimates of releases and transport are reasonable. Thorough review of historical records and extensive interaction with former and curren t employees and residents have been the foundation for reconstructing routine operations, documenting accidents, and evaluating unmonitored emission sources. The largest releases of uranium to air and water occ urred in the 1950's and 1960's. Radon releases from the silos remained elevated through most of the 1970's. The quantity of uranium released to surface water was much less than that released to air. Best estima tes of releases are reported as median values, with associated uncerta inties calculated as an integral part of the estimates. Screening calc ulations showed that atmospheric pathways dominate the total dose from Feed Materials Production Center releases. Accordingly, the local met eorology, effluent particle size and chemical form, and wet and dry de position, were particularly important in this study. The final goal of the project is the calculation of radiation doses to people living in the study domain, which is represented by a circle with radius of 10 km centered on the Feed Materials Production Center production area.