[2B01-04] Geological disposal

10:00 AM - 10:15 AM JST(1:00 AM - 1:15 AM UTC)

[2B03] Overview of a full-scale construction experiment on hydraulic plugs for sedimentary rock at the Horonobe URL(3) Investigation of the excavation damaged zone and hydrogeological structures around the tunnel for hydraulic plug design

*Akira Hayano¹, Shun Kimura¹, Tomonori Tamura¹, Keisuke Yagi² (1. JAEA, 2. TAISEI)

Keywords:

High-level radioactive waste disposal,Hydraulic plug,Excavation Damaged Zone,Horonobe Underground Research Laboratory

During repository closure, hydraulic plugs with low-permeability materials are being considered to reduce radionuclide migration through the EDZ around tunnels. This study investigated EDZ distribution and hydraulic properties at 350 m Niche No. 6 of the Horonobe URL, where an in situ hydraulic plug construction experiment is planned in sedimentary rock. Borehole investigations in 20 holes and geological mapping of part of the tunnel floor showed that EDZ fractures are concentrated on the eastern side and extend up to about 1.5 m from the tunnel wall. Hydraulic conductivity was locally three to four orders of magnitude higher than in intact rock. These results will be incorporated into the design of the hydraulic plug geometry and dimensions.