Outline of the disposal of very low level concrete waste in JAEA

極低レベル放射性コンクリート廃棄物の埋設処分の概要

辻 智之 

Tsuji, Tomoyuki

JAEAでは原子力科学研究所にあったJPDRの解体実地試験に際し、極めて放射能レベルの低いコンクリート廃棄物の埋設実地試験を行った。約1,700トンの極低レベルコンクリート廃棄物が45m16m、深さ3.5mの素掘りの埋設用トレンチに定置され、2.5m厚さの土砂で覆われた。極低レベルコンクリート廃棄物の埋設実地試験は埋設段階(19951996年)及び保全段階(19962024年)に分けられる。埋設段階では、埋設処分施設の周辺の放射線量の測定、地下水,覆土の放射能分析が行われた。保全段階へと移行した後も、さらに3年間放射能モニタリングを継続した。また、覆土の流出,亀裂,陥没がないこと等を毎週1回の巡視点検により確認し埋設処分施設の維持・管理を行っている。放射能モニタリングデータの記録については保全段階が終了するまで廃棄物管理部署で適切に保存する計画であり、巡視点検の記録については核原料物質、核燃料物質及び原子炉の規制に関する法律に基づいて保存している。

Japan Atomic Energy Agency (JAEA), who conducted the demonstration test on a safe dismantling of Japan Power Demonstration Reactor (JPDR) in Nuclear Science Research Institute, has been performing the safe demonstration test of near-surface disposal of very low level (VLL) concrete waste arising from JPDR dismantling. Approximately 1,700 tons of VLL concrete wastes were placed in a simple disposal facility, of which dimensions are 45 m16 m and 3.5 m in depth without any engineered barrier, and covered with soil of 2.5 m thickness. The safe demonstration test of near-surface disposal of VLL concrete waste consists of a operation stage (FY 1995-1996) and a management stage (FY 1996-2024). In the operation stage, radiation dose around the disposal facility was measured, and radioactivity concentrations in groundwater and soil were analyzed. After we proceeded the management stage of disposal, radiation monitoring was continued additionally for 3 years in the management stage. An inspection such as no outflow, crack and subsidence of the covered soil is conducted at once a week. The radiation monitoring data is planned to storage properly by management department until the finishing of management stage, and an inspection data is stored in accordance with the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors.