- Implementation Guidance for SSHAC Level 3 & 4 Processes
- K.J. Coppersmith ; J.J. Bommer ; A. Kammerer ; J.P. Ake
- Book Title / Journal: 10th International Probabilistic Safety Assessment & Management Conference
- Year: 2010
- Risk & Reliability
- Keywords: PSHA ; Epistemic uncertainty ; SSHAC
- Risk analysis for critical facilities requires a probabilistic assessment of the hazards that could affect the installation. The complexity of the processes that generate geological hazards such as seismic ground shaking and volcanic events is such that there is inevitably large uncertainty associated in the hazard assessment. This uncertainty is reflected in the range of legitimate technical interpretations made by informed technical experts based on the available data. Procedures to develop multiple expert assessments for seismic hazards in a structured process have been established in the SSHAC (Senior Seismic Hazard Analysis Committee) guidelines. The objective of the present paper is to capture and clarify the insights gained from performing a number of detailed assessments using the SSHAC approach over the past 10-15 years. Unlike classical expert elicitation, which attempts to extract information from independent experts, the SSHAC process encourages interaction amongst experts and fosters learning by the experts throughout the process, with the ultimate objective of capturing the full community distribution of technical interpretations. The SSHAC guidelines, written largely in abstract, have now been implemented in practice several times. In these studies valuable lessons have been learned, which are now being distilled into a new U.S. Nuclear Regulatory Commission NUREG-series report to provide practical guidance on implementing SSHAC processes for hazard assessments. A key lesson from these studies is that higher level SSHAC processes (Levels 3 and 4) which specify the use of a Participatory Peer Review Panel (PPRP), provide a higher degree of regulatory assurance and stability for the initial development of hazard models for safety-critical installations. Also, significant technically-informed participation by project sponsors and regulators throughout the process enhances the likelihood of regulatory acceptance.