Radiocaesium pollutants on the pinecones contaminated were measured by a germanium semiconductor detector and autoradiography in 2013–2015. The 137Cs concentration of gray pinecone in 2015 around Fukushima Prefecture was high and they were weak correlations between the dose rate map of November, 2011 and some strongly spot were shown in the autoradiography. It was thought that the falling gray pinecones of Pinus densiflora were including high radiocaesium pollution in Northern Fukushima Prefecture after 2015 for a while.
According to the research conducted by the Government of Japan and Chiba Prefectural Government, the sediments of Lake Tega and its tributaries are still highly contaminated by radiocaesium (over 1,000 Bq/kg) derived from the Fukushima Daiichi Nuclear Power Plant. To investigate the possible sources that would transport and redistribute radiocaesium to the Lake Tega system, which is urbanized compared to Fukushima Prefecture, we have selected three retention basins, corresponding to upstream of Lake Tega, located in Kashiwa City, Chiba Prefecture. Temporal changes in concentrations of radiocaesium in water and sediment samples were determined during 2013–2014. The concentrations of radiocaesium in both samples tended to decrease during the sampling period, although some of the sediment samples were still high radiocaesium concentrations exceeding 10 kBq/kg. These observations suggest that the radiocaesium in the retention basins, which play an important role in supplying radiocaesium to the downstream area, is highly contaminated compared to the downstream area. Increments of the concentrations of radiocaesium in particulate form were observed from the water samples collected immediately after the passage of large typhoon Wipha. This result implies that heavy rainfall events may be playing an important role in the migration of existing radiocaesium from the catchment areas to the Lake Tega system.
A method is studied of obtaining highly concentrated 99mTc solution from 99Mo to be produced by 98Mo(n, γ)99Mo reaction. After extraction of 99mTc with MEK from 99Mo/99mTc alkaline solution and purification of 99mTc with basic alumina column, 99mTc is adsorbed to acidic alumina column and eluted from that. In this study, a preliminary study of examining performance of 99mTc for adsorption and elution with acidic alumina was carried out using inactive Re instead of 99mTc. The amounts of Re corresponding to 15 TBq levels of 99mTc were used for 7 g of acidic alumina packed in 12 mmϕ and 14 mmϕ columns. Effect of flow rates on some effluents used was also examined.The results show that the amounts of Re corresponding to 2.5 TBq from 36.7 TBq can be favorably adsorbed to acidic alumina column and eluted from it in a short time, slightly depending on the amounts of Re treated. Finally, it made clear that acidic alumina column is applicable to the mass production of highly concentrated 99mTc solution from (n, γ)99Mo in the levels of about 15 TBq to be handled in JMTR.