Sequential estimation of Ru-106, Cs-137, and Sr-90 in urine

A sequential method has bren developed for the estimation of Ru-106, Cs-137 and Sr-90 in urine using beta counting. After completely destroying the organic matter in urine, Ru-106 is oxidized to volatile ruthenium tetroxide and allowed to react in-situ with polyethylene powder; Cs-137 is concentrated on ammonium phosphomolybdate and estimated as tetraphenylborate; Sr-90 is coprecipitated as strontium sulphate and converted to carbonate. The recoveries have been found to be better than 83% for all of the radionuclides. The minimum detection limits are 0.16, 0.85, and 0.14 Bq/dm(3) for Ru-106, Cs-137, and Sr-90, respectively. Yttrium-90 fraction of Sr-90 is also estimated using sodium nitroprusside as reagent, after allowing it to grow for 14 days.