CONSIDERATION ON NEAR-FIELD BEHAVIORS AND LAYOUT ELEMENTS OF A DEEP REPOSITORY FOR HIGH-LEVEL RADIOACTIVE-WASTES

Based on the recognition that layout elements of a repository are impo rtant factors to govern total costs of the high-level radioactive wast e disposal, the study on their feasibility has made as a trial from th e view points of economics, shielding, strength against pressure, rete ntion capability and especially mechanical interactions within near-fi eld under some premises and conditions discribed below to establish an economical and rational repository concept. (1) Host rocks : Granite (800m deep) and sedimentary (500m deep) (2) Emplacement methods : Hori zontal (3) Thickness of overpacks : 20cm (4) Thickness of bentonite : 70cm (5) Inner diameter of repository tunnel : 2.3m (6) Center distanc e between repository tunnels : 20m In addition, perceiving long-term b ehaviors of near field composed of waste package, overpack, bentonite and surrounding rock, some suggestions or tasks for each items above a re also referred. Among assumptions for these studies, there are some items, such as corrosion rate and performance of overpack, as well as mechanical properties of bentonite and so on, not confirmed fully yet by experiments, and so studies are made under conservative assumptions for these items. Considering study results as a whole, the premises a nd conditions specified in these studies are concluded to be highly fe asible.