Horonobe Underground Research Laboratory project synthesis of phase I investigations 2001 - 2005. Volume 'Geoscientific research'

Abstract

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formations at Horonobe in Hokkaido, northern Japan. The project consists of two major research areas, 'Geoscientific Research' and 'R and D on Geological Disposal', and proceeds in three overlapping phases, 'Phase I: Surface-based investigation', 'Phase II: Construction' and 'Phase III: Operation', over a period of 20 years. The present report summarises the results of the Phase I geoscientific research carried out from March 2001 to March 2005. Integration of the results from different disciplines ensures that the Phase I goals have been successfully achieved and identifies key issues that need to be addressed in Phases II and III. More importantly, efforts are made to summarise as many lessons learnt from the Phase I investigations and other technical achievements as possible to form a 'knowledge base' that will reinforce the technical basis for both implementation and the formulation of safety regulations. Based on experiences of selecting the URL area and site in Horonobe Town, important factors that should be taken into consideration in such selection processes and their rationale are demonstrated. In the course of stepwise surface-based investigations, a number of achievements have been made, which can eventually provide examples of integrated methodologies for characterising the sedimentary formations. The relevant surface-based investigation techniques have thus been further developed. The Horonobe URL has been designed based on geoscientific information accumulated during the surface-based investigations and the plans for safe construction and operation of the URL have been defined in a feasible manner. In addition, a variety of environmental measures taken during Phase I have proved to be effective on minimising the environmental impact induced by URL construction. (author)