Cherenkov counting of 90 Sr and 90 Y in bark and leaf samples collected around Fukushima Daiichi Nuclear Power Plant

The radioactivity of 90 Sr and 137 Cs in environmental samples, bark and leaf, collected around the Fukushima Daiichi Nuclear Power Plant in May 2013 was determined with the aim of investigating the migration of both nuclides using their radioactivity ratio. The radioactivity of 90 Sr was determined by using Cherenkov counting of 90 Y after purification using Sr resin and that of 137 Cs was determined by γ-spectrometry. Quench correction in Cherenkov counting was investigated by measurements of samples spiked with purified 90 Y revealed that the radioactivity could be evaluated without quench correction. The radioactivity ratio of 90 Sr to 137 Cs in bark samples of 4.2 × 10 −3 and 1.2 × 10 −2 was compared with the results from soil samples collected in July 2011 to show that the migration of 90 Sr was slower than 137 Cs in bark and tree.