International trends on stylization of biosphere evolution and future human activity for performance assessment of geological disposal

Regulatory guidelines are usually established concerning the dose assessment of geological disposal, based on the Reference Biosphere Methodology by IAEA BIOMASS project and radiological criteria applied to scenarios representing natural processes and human intrusion by ICRP. Based on these regulatory guidelines, responsible organizations or research institutes of geological disposal develop dose assessment scenarios for performance assessment of geological disposal. It is difficult to assume future evolutions of surface environments and human activities accurately and to describe them in a biosphere assessment scenario of geological disposal. Accurate assumption on their evolution is not reasonable, because a biosphere assessment aims to illustrate the radiological impact to human as an index of performance for repository. Consequently, it is important to develop the methodology to describe the biosphere system with long-term evolution of geosphere according to a regulatory guideline or an assessment purpose, that is, the methodology to stylize evolutions of surface environments and human activities. In this report, the author reviewed regulatory guidelines and scenarios of performance assessment applied to natural processes and human intrusion in foreign countries, and discussed the view-points when evolution of biosphere and future human activity are stylized in performance assessment of geological disposal. (author)