The determination of low levels of radiocaesium and radioruthenium in foodstuffs

Abstract

The Ministry of Agriculture, Fisheries and Food (MAFF) has the responsibility for safeguarding the food supply from authorised and accidental releases of radioactivity to the environment. MAFF funds a radiological research programme to assist in the achievement of its objectives and has recognised that there is a continuing requirement to develop cost effective and sensitive analytical methods for the detection of very low levels of radioactivity in foodstuffs. High resolution gamma spectrometry is often the most appropriate analytical method for the determination of 103Ru, 106Ru, 134Cs and 137Cs but the detection limits for these radionuclides in bulk foodstuffs do not permit the acquisition of accurate data at very low levels. Beta counting techniques offer inherently higher sensitivities but the development of radiochemical separation techniques is essential to provide appropriate counting sources. A radiochemical separation method has been developed for the determination of radiocaesium and radioruthenium in 0.5 kg fresh wt samples of a variety of foodstuffs. The method was shown to be robust and specific and mean method recoveries of 75% were obtained for both radiocaesium and radioruthenium. MDA's for the 1000 min counts on a gas-flow proportional counter were determined to be 0.015 Bq/kg fresh wt for both 137Cs and 106Ru.