@misc{oai:repo.qst.go.jp:00070521,
 author = {Ishii, Nobuyoshi and Tagami, Keiko and Ogiyama, Shinichi and Sakurai, Shinji and Uchida, Shigeo and 石井 伸昌 and 田上 恵子 and 荻山 慎一 and 櫻井 伸治 and 内田 滋夫},
 month = {Jun},
 note = {Transuranic (TRU) waste containing radionuclides is generated during the operation and dismantling of reprocessing facilities and mixed oxide (MOX) fuel fabrication facilities.  In Japan, TRU waste for geological disposal is categorized into four groups in accordance with physical properties and the concentration of radioactive materials.  Group 2 waste among four groups of TRU waste includes hull and end piece wastes, which are comprised of the debris and residue from the shearing and dissolution of the spent fuel assemblies.  The key nuclide in a geological repository for Group 2 waste is 14C, and leaching of 14C -organic materials from simulated hull wastes has been reported.  Because 14C is long-lived and has very little sorption properties, the possible migration of 14C from a TRU repository site to the biosphere through groundwater presents some concern.  Therefore, it is necessary to understand the behavior of 14C in the human habitation sphere on the assumption the 14C derived from TRU wastes.  In our research project, soil-soil solution distribution coefficients (Kd) and soil-to-rice plant transfer factors (TF) of 14C have been determined by laboratory experiments to clarify the behavior of 14C in Japanese rice paddy fields.  Acetic acid as a 14C source in irrigated paddy soils was rapidly incorporated and decomposed by soil microbes.  Although the most of the 14C was released into the air as gas forms, some of the 14C was assimilated into the microbial cells.  The main chemical species of 14C gas released into the air was 14CO2, and a part of the 14CO2 could be used by photosynthesis of the rice plants.  Only a small amount of the 14C was absorbed through the roots.  The transferred 14C to the rice plants was detected even in white rice.  Human expose to 14C through rice intake must be considered in the safety assessment of TRU waste disposal.  This work has been partially supported by the Agency for Natural Resources and Energy, the Ministry of Economy, Trade and Industry (METI), Japan., 56th Annual Meeting of the Health Physics Society},
 title = {Behavior of 14C-organic materials in Japanese paddy fields},
 year = {2011}
}