Observation and measurement of 79Se in Savannah River Site high level waste tank fission product waste

First observation of confirmed 79Se activity in Savannah River Site high level fission product waste is reported. 79Se was measured after a seven step chemical treatment to remove interfering activity from 137Cs, 90Sr, and plutonium at levels 105 times higher than the observed 79Se content and to remove 99Tc at levels 300 times higher than observed 79Se. 79Se was measured by liquid scintillation β-decay counting after specific tests to eliminate uncertainties from possible contributions from 99Tc, 147Pm, 151Sm, 93Zr, or 241Pu, whose β-decay spectra could appear similar to that of 79Se, and whose content would be expected at levels near or greater than 79Se. (author)