A Study on time frame definition and reference evolution of the geological system for safety assessment; Case study on the Horonobe URL site

Kurikami, Hiroshi ; Niizato, Tadafumi ; Yasue, Kenichi

Description of system evolution is an important task in safety and investigation strategies. This paper showed the method to describe system evolution based on safety functions and FEPs and its application to the Horonobe site. Based on the SDM and the Horonobe-specific FEPs, the important FEPs were put in a timeline with the main safety functions. According to the FEPs, we defined thermal and resaturation phase, steady geology phase and geologically evolution phase. In the steady geology phase, the functions of retardation and dilution in the deeper part of the Wakkanai Formation are important, therefore, advection, dispersion and sorption in the domain should be assessed based on the nuclide migration scenario. In the geologically evolution phase, the uplift and denudation are important. Thus, the uplift, denudation and the consequent THMC processes were involved in the reference evolution. Through the application and the discussion, the method was found to be applied to other sites.