The 13th International Conference on Environmental ... - Events

Abstracts
A critical issue for building confidence in the long-term safety of geological disposal is to demonstrate the stability
of the geosphere, taking into account its likely future evolution. This stability is broadly defined as the persistence of
<strong>The</strong>rmal-Hydrological-Mechanical-Chemical conditions considered favourable for the long-term safety of a geological
repository. <strong>The</strong> geosphere is slowly but constantly evolving, and then the stability, in this case, does not imply that
steady-state conditions exist. What is important is that the evolution of the geosphere can be understood. In general, an
understanding of the evolution is gained by studying the palaeohydrogeological evolution of a site, defining temporal and
spatial changes of various characteristics, events, and processes over geological time. <strong>The</strong> site palaeohydrogeology refers
to natural events and processes that have occurred in the past and contributed to the present state of the geosphere, which
include sub-surface processes (e.g. crustal movement, diagenesis, etc.) and earth-surface processes (e.g. climatic and
sea-level changes, geomorphological processes, etc.). An understanding of the palaeohydrogeological evolution of the
site provides the firm foundation to describe the likely future evolution of the site. An ongoing collaborative programme
aims to establish comprehensive techniques for characterising the overall evolution of coastal sites through studying the
palaeohydrogeological evolution in the coastal system around the Horonobe area, Hokkaido, northern Japan. In this study,
the current status for the conceptualisation of the long-term geosphere evolution in the coastal area, is based on data from
the JAEA’s underground research laboratory project. Information on surface and sub-surface processes has been
integrated into a chronological conceptual model which indicates space-time sequences of the events and processes in the
area over geological time. Spatial scale for the conceptualisation is ca. 100 km in the East-West direction through the
locations of the underground research laboratory and of the borehole investigations on the coast in the Horonobe area.
Temporal conceptualisations over the last few million years are focused on the spatial and temporal changes of the
geosphere caused by sub-surface processes and over the last several hundred thousand years focused on the changes
caused by earth-surface processes. <strong>The</strong> methodology for conceptualisation of the geosphere evolution will be applied to
other analogous coastal areas on Japan’s western seaboard to produce comprehensive techniques to support
understanding the geosphere evolution of potential coastal sites for deep geological repositories.
6) 40048 – Development of Comprehensive Techniques for Coastal Site Characterisation (2) Integrated
Palaeohydrogeological Approach for Development of Site Evolution Models
Kenji Amano, Tadafumi Niizato, Hideharu Yokota, Kunio Ota, JAEA (Japan);
Bill Lanyon, Nagra (Switzerland);
W Russell Alexander, Bedrock Geosciences (Switzerland)
Radioactive waste repository designs consist of multiple safety barriers which include the waste form, the canister,
the engineered barriers and the geosphere. In many waste programmes, it is considered that the three most important
safety features provided by the geosphere are mechanical stability, favourable geochemical conditions and low
groundwater flux. To guarantee that a repository site will provide such conditions for timescales of relevance to the
safety assessment, any repository site characterisation has to not only define whether these features will function
appropriately today, but also to assess if they will remain adequate up to several thousand to hundreds of thousand years
into the future, depending on the repository type.
In general, this is done by studying the palaeoKHNPgeological evolution of a site, defining temporal and spatial
changes of various characteristics and processes. <strong>The</strong>se may include hydrogeology, geology, groundwater flow
characteristics, groundwater chemistry and site tectonics, including uplift and erosion processes. <strong>The</strong>se key aspects are
studied to build up a conceptual model for the overall site evolution over geological time, up to the present and this is
used to define the likely future evolution of the site and to assess if the main safety features will continue to function
adequately.
<strong>The</strong> collaborative programme described here is focussed on the palaeohydrogeology of the coastal area around
Horonobe in northern Hokkaido, Japan. Data from JAEA’s ongoing underground research laboratory project is being
synthesised in a Site Descriptive Model (SDM) with new information from the collaborating research institutes to
develop a Site Evolution Model (SEM), with the focus very much on changes in the Sea of Japan seaboard over the last
few million years. This new conceptual model will then be used to assess the palaeohydrological evolution of other
analogous sites on Japan’s western seaboard, with the final aim of producing a set of comprehensive techniques to
understand the palaeohydrogeological evolution of the deep geosphere of all coastal sites on the Sea of Japan.
7) 40041 – Development of Methodology of Groundwater Flow and Solute Transport Analysis in the Horonobe
Area, Hokkaido, Japan
Keisuke Maekawa, Hitoshi Makino, Hiroshi Kurikami, Tadafumi Niizato, Manabu Inagaki,
Makoto Kawamura, JAEA (Japan)
It is important for establishment of safety assessment techniques of geological disposal to understand groundwater
flow and solute transport accurately. <strong>The</strong>refore, we are positioning to confirm an applicability of the techniques in
realistic environment as a crucial issue in R&D. We have attempted and planed some relevant studies as below: -A
methodology to integrate activities from site investigations to evaluation of solute transport was examined. We have
carried out groundwater flow analysis on a regional scale using geological and hydrological information from
surface-based investigations at the Horonobe area, and also solute transport analysis based on the information of the
trajectory analysis. -We have carried out a preliminary simulation of groundwater flow and salinity concentration
distribution using information on climatic and sea-level changes, and evolution of geological structures considering the
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