Basic Characteristic Test of Buffer / Backfill Material under Horonobe Groundwater Condition

Kikuchi, Hirohito*; Tanai, Kenji 

By the second progress report (H12) on research and development for the geological disposal of HLW in Japan, Japan Nuclear Cycle Development Institute (JNC) extended the database on basic properties of compacted bentonite, and this was mainly obtained by using distilled water as test fluid. This report presents influence of Buffer and Backfill material on the Basic properties under Horonobe groundwater, which was simulated by use of synthetic seawater. In the Horonobe groundwater targeted in this report, the groundwater of GL-300m or less was used bore hole HDB-6 of the underground laboratory of Horonobe construction site neighborhood. In addition, it examined it by using distilled water, synthetic seawater, and NaCl solution. Experimental results are as follows ; 1)Swelling characteristics, Hydraulic characteristics, and Mechanical characteristics of the buffer material and backfill material specification decrease by the influence of saline water. The relationship between effective clay density and swelling stress is obtained by the following equation. The relationship between effective clay density and intrinsic permeability is obtained by the following equation. The relationship between effective clay density and unconfined compressive strength is obtained by the following equation. 2)Saline water doesn't influence the heat characteristic of the buffer material specification. The thermal conductivity and specific heat are appreciable by the relational expression that uses include water content that has been obtained so far.