Calculation of the Inventory and Near-Field Release Rates of Radioactivity from Neutron-Activated Metal Parts Discharged from the High Flux Isotope Reactor and Emplaced in Solid Waste Storage Area 6 at Oak Ridge National Laboratory

摘要

Emplacement of contaminated reactor components involves disposal in lined and unlined auger holes in soil above the water table. The radionuclide inventory of disposed components was calculated. Information on the composition and weight of the components, as well as reasonable assumptions for the neutron flux fueling use, the time of neutron exposure, and radioactive decay after discharge, were employed in the inventory calculation. Near-field release rates of sup 152 Eu, sup 154 Eu, and sup 155 Eu from control plates and cylinders were calculated for 50 years after emplacement. Release rates of the europium isotopes were uncertain. Two release-rate-limiting models were considered and a range of reasonable values were assumed for the time-to-failure of the auger-hole linear and aluminum cladding and europium solubility in SWSA-6 groundwater. The bounding europium radionuclide near-field release rates peaked at about 1.3 Ci/year total for /sup 152,154,155/Eu in 1987 for the lower bound, and at about 420 Ci/year in 1992 for the upper bound. The near-field release rates of sup 55 Fe, sup 59 Ni, sup 60 Co, and sup 63 Ni from stainless steel and cobalt alloy components, as well as of sup 10 Be, sup 41 Ca, and sup 55 Fe from beryllium reflectors, were calculated for the next 100 years, assuming bulk waste corrosion was the release-rate-limiting step. Under the most conservative assumptions for the reflectors, the current (1986) total radionuclide release rate was calculated to be about 1.2 x 10 sup -4 Ci/year, decreasing by 1992 to a steady release of about 1.5 x 10 sup -5 Ci/year due primarily to sup 41 Ca. 50 refs., 13 figs., 8 tabs. (ERA citation 12:049424)