ENVIRONMENTAL SR-90 MEASUREMENTS

Sr-90 (T-1/2 = 28.5 years) is a long-lived radionuclide produced in nu clear fission. Fast radiochemical detection of Sr-90 in environmental samples is not feasible using current analytical methods. Accelerator Mass Spectrometry (AMS) measurements of Sr-90 were made with the Rehov ot 14UD Pelletron accelerator at a terminal voltage of 11 or 12 MV usi ng our standard detection system, Injection of hydride ions (SrH3-) wa s chosen owing to high beam intensity and low Coulomb explosion effect s. Sr-90 ions were identified and discriminated from isobaric Zr-90 by measuring time of flight, total energy and three independent energy-l oss signals in an ionization chamber, A reference sample and a ground- water sample were successfully measured. The detection limit determine d for a laboratory blank by the residual counts in the Sr-90 region is Sr-90/Sr = 3 x 10(-13), corresponding in practice to (2-4) x 10(7 90) Sr atoms or about 0.5-1 pCi/L samples.