Measurement of 90Sr in reactor wastes by Cerenkov counting of 90Y

Abstract

Determination of 90Sr in low-level radioactive wastes (LLW) from reactors is difficult because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy [beta]-particle emissions of 90Y in order to quantitate 90Sr. Separation of this important nuclide in low-level waste samples was by solvent extraction using tri-n-butyl phosphate. Since most beta emitters in LLW from commercial nuclear power facilities are below about 1 MeV, Cerenkov counting with a high-discriminator setting provided accurate quantitation without interference of potential contaminants which were either removed by separation or discriminated against by the counting procedure. A tracer of 85Sr was used and the radiochemical yield was 59.6 +/- 1.9%; the lower limit of detection was found to be 1.48 pCi/g based on a 10 g sample and a 20-min counting time.