Developing Advanced Technologies and Human Resources Towards Implementation of Geological Disposal: The Horonobe International Project (HIP)

The Horonobe International Project (HIP) is an OECD NEA (Organisation for Economic Co-operation and Development - Nuclear Energy Agency) Joint Project running from February 2023 to March 2029. It includes 11 organisations from Asia, Australia, and Europe. HIP‘s main objectives are to 1) develop and demonstrate advanced technologies to be used in repository design, operation and closure, and a realistic safety assessment for deep geological disposal; and 2) encourage and train the next generation of engineers and researchers by sharing and transferring the knowledge and experience developed to date in the participating organisations.

HIP is conducted as a part of the Horonobe underground laboratory (URL) project in Horonobe town (northern Hokkaido, Japan). This project is in operation since 2001 in Neogene sedimentary rocks. It is a pure research and development laboratory (i.e., generic URL) for the final disposal of radioactive waste, which is not used as a final disposal site. HIP is divided into three main tasks:

Task A „Solute transport experiment with model testing“ develops realistic 3D solute transport models that can be applied to repository safety assessments for fractured porous sedimentary rocks. First in-situ (including tracer experiments) and laboratory experiments (diffusion and sorption experiments) provide basic characteristics of structures and processes relevant for solute transport. Based on these results, further in-situ experiments will validate and optimise the numerical and conceptual models for solute transport in fractured sedimentary rocks.

Task B „Systematic integration of repository technology options“ 1) develops and tests technology options for repository operation; 2) establishes the concepts and criteria for locating disposal pits or holes in suitable rock domains around the disposal tunnels; and 3) demonstrates the systematic integration of available technology options to arrange and construct the disposal pits or holes. Part of Task B is also the excavation of new galleries at 500 m depth including operational near-field exploration. So far, numerical models for the prediction of cracks, the inflow of groundwater and the development of the excavated damage zone have been developed.

Task C „Full-scale EBS dismantling experiment“ builds on the full-scale EBS (Engineered Barrier System) performance experiment for vertical emplacement, which has been carried out at the 350 m gallery since 2014. It aims to understand the thermal-hydrological-mechanical-chemical (THMC) coupled processes in such an EBS and to test and verify different THMC simulation codes based on monitoring data gained during the EBS experiment and its subsequent dismantling.

Results and experience of all above described tasks support the partnering institutions in the safety assessments for deep geological disposal of radioactive waste. In the context of the German site selection procedure for high-level radioactive waste, the results from HIP will support the further-developed preliminary safety analyses. The presentation will also highlight BGE's interests and contributions to the three tasks.