Measurement of 90Sr activity in Fukushima soil samples affected by Nuclear Accident

Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released β particle emitter fission product, 90Sr, along with gamma emitter nuclides, such as 137Cs, 134Cs, 131I, 132Te into environment. 137Cs, and 90Sr have long-lasting radioecological impact due to their longer half-life (>30 y). Furthermore, the 90Sr has long biological half-life (˜18 y) in the human body. Due to its chemical similarity to calcium it accumulates in bones and irradiates the bone marrow, causing its high radio-toxicity.Assessing 90Sr in the environment is therefore necessary in case of a nuclear disaster. For 90Sr measurement, a new separation laboratory was established at the National Institute for Quantum and Radiological Science and Technology, Japan (QST) in 2012. Fukushima soil samples were collected in 2013. We have observed a weak correlation between 90Sr and 137Cs activity concentrations in samples (Figure 1), however, the 90Sr concentration was lower with three or four magnitudes than 137Cs.In this presentation, a soil sample collection survey in the Fukushima exclusion zone was accomplished in 2016 and some contaminated hot spots were revealed with air dose rate measurement (>20 µSv/h). In the collected soil samples, 137Cs activity concentrations were over 1000 Bq/g while the 90Sr were over 500 Bq kg 1.ENVIRA 2017 (International Conference on Environmental Radioactivity