廃棄物処分のナチュラルアナログ研究

あまりアナログにこだわるな

抄録

Studies on natural analogues are indispensable ways to define geological disposal concepts, and to provide convincing support for the performance assessment of long-term radioactive isolation. Long-term predictions on the behavior of the natural environment are recognized to be fraught with uncertainty if based solely on information from limited and short-term observations or experiments. In this context, natural analogue studies have been extensively carried out by many researchers in the world. However, natural analogue studies have been recently scaled down and financially limited due to: (1) limited study areas that are systematically analogous to disposal sites, which is the primary prerequisite for analogue studies; (2) deficiency in defining natural analogues; and (3) lack of clarity on the utilization of data obtained in the studies and how it can contribute to performance assessment.
Recent issues surrounding the performance assessment that should be addressed urgently in assessing the impacts on the disposal systems include: (1) retardation of anionic species such as ¹⁴CO₄^2-, H⁷⁹SeO₃^-, ⁹⁹TcO₄^-; and (2) bentonite-hyper alkaline fluid (i.e. cement pore fluid) interactions. If the criteria for natural analogue studies are strictly defined, it would be very difficult to find suitable study areas. In this review, the required conditions and strategies for future natural analogue studies are discussed and summarized based on case studies of natural attenuation of arsenic in acid mine drainage and mineral paragenesis under hyper alkaline condition in Oman ophiolite.