Quantification of Radionuclide Migration Parameters in Safety Assessment of Radioactive Waste Disposal: Review on the Use of Expert Elicitation

Abstract

Expert elicitation has traditionally been accepted in some countries as a way to quantify the uncertainty of radionuclide migration parameters in the safety assessment of radioactive waste disposal. However, expert elicitation has not yet been explicitly performed in the field of radioactive waste disposal in Japan. To discuss the applicability of expert elicitation in Japan, here we broadly review the histories and methodologies of expert elicitation in some papers and review in more detail case studies on the utilization of expert elicitation in the safety assessment of radioactive waste disposal in the US, UK, and Sweden. From the literature review, we suggest that it is valuable to adopt expert elicitation to quantify the uncertainty of parameters in Japan. In particular, the documentation of each elicitation step is critical to ensuring the traceability and transparency of expert elicitation. The documentation enables the regulator to evaluate whether the expert judgment including the elicitation process is adequate. Furthermore, we recommend providing not only an aggregated expert judgment for safety assessment but also the distribution of individual expert judgements. Individual expert judgments will be used for related analyses (e.g., sensitivity or uncertainty analyses), leading to increased confidence in the safety assessment.