Scenario development on application of engineering technology for geological disposal; Study on accidents and human factors caused at site characterization, construction, operation and closure stages and that impact on safety functions after closure of disposal facility (Contract research)

Takayama, Hideki*; Takai, Shizuka ; Takeda, Seiji 

In the safety assessment for the high-level radioactive waste geological disposal, scenarios need to be developed in consideration of influence on barrier features by applying engineering technologies at each stage of site selection, construction, operation and closure of disposal facility. To develop scenarios on application of engineering technologies from the point of view of safety regulation, it is important to grasp information of the engineering technologies which are possibly applied to geological disposal and to organize relationships between accidents and human factors caused by application of engineering technologies and influence by the factors on safety functions of engineered and natural barriers after closure stage. In this study, the engineering technologies are listed for site selection, construction, operation and closure activities at disposal site. From this information, "deviation events" which are deviated states of engineered and natural barriers from intended design were identified. We assumed influence on geological disposal facility due to the occurrence of the deviation events and identified the accidents and human factors which can progress the deviation events. Finally, we showed the sequence of influence by the accidents and human factors on long-term safety after closure of the disposal facility as scenarios. We provided a database with these results for development of scenario on engineering technology of geological disposal.