Determination of trace radionuclides in depleted uranium recovered from irradiated target element reprocessing

NUCL 42

Donna M. Beals, Steven P. LaMont, James R. Cadieux, Chuck R. Shick, and Greg Hall. Savannah River Technology Center, Westinghouse Savannah River Company, Building 735-A, Aiken, SC 29808

Savannah River Site depleted uranium (DU) required the radioactivity level of 241Am, 238Pu through 242Pu, 237Np, 226Ra, 137Cs, 129I, 99Tc and 90Sr to be determined prior to off-site waste shipment. Methods were developed to measure these radionuclides with detection limits on the order of a few tens of pCi/g of DU. After chemical separation, 241Am, 226Ra, 137Cs and 129I were determined by gamma spectroscopy in an ultra low-level counting facility. Strontium-90 was measured by gas flow proportional counting, 99Tc by liquid scintillation counting, and 237Np and 238Pu by alpha spectrometry. The remaining Pu isotopes were determined by high sensitivity thermal ionization mass spectrometry. Technetium-99 was the only radioisotope detected significantly above the detection limit. The uranium isotopic abundances were determined by alpha spectrometry; selected samples were analyzed by mass spectrometry in order to determine the 236U separately from the 235U.