safety

Topaz

The TOPAZ (Tectonics Of Potential Assessment Zones) Project

ITM (2004 – 2009)

The ITM Project focused on evaluating comparative tectonic hazards to possible siting regions for geological repositories for radioactive wastes in Japan and their evolution for the next 100,000 years. The principal hazards assessed were rock deformation and new volcanism. Regional Case Studies for Tohoku and Kyushu were used to develop and test the methodology for significantly differing tectonic conditions (relatively simple arc tectonics in Tohoku compared to complex and rapidly changing tectonic conditions in Kyushu).

ITM (2010 – 2013)

The Topaz Project (Tectonics Of Potential Assessment Zones) developed and extended the ITM methodology. Alternative conceptual models were used to characterise how the tectonic situation in a region might develop over at least 1 million years into the future and attaching expert degrees of belief to ‘Regional Evolution Scenarios’ (RES), using a formal expert elicitation methodology. These, in turn, were used to develop ‘Site Evolution Scenarios’ (SES), which describe how an RES might ‘play out’ at a specific location. The degrees of belief in different scenarios were expressed as probabilities in a logic tree and were superimposed on the event probabilities derived from the ITM methodology to arrive at probabilities of specified impacts in different timeframes. The output was used to produce Hazard Maps of large regions of Japan for different future time periods.

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