Status of design for the impermeable layer installed the trench disposal facility for low level radioactive waste

Sakai, Akihiro 

The impermeable layer installed in trench disposal facility was designed in order to dispose of radioactive waste other than concrete and metal waste generated from research facilities, etc. In study of material of impermeable liners, weathering test in equivalent to long time was done. The test results showed that the tensile strength and the elongation percentage of HDPE that is a high elasticity type liner met standard values. However, the tensile strength of MEPE that is a medium elasticity type liner did not meet the standard value. The seepage water through several models of impermeable layers were calculated by use of the HELP code developed in U.S. The results showed that the structure that was composed of double impermeable liners, a drainage layer on the upper liner, and an impermeable sheet between the liners can be expected to have the enough performance to restrict seepage water.