Confidence in Geosphere Performance-assessment- The Canadian Nuclear Fuel Waste Disposal Programme 1981-1999: A Retrospective

摘要

In March 1998 a federal Environmental Assessment Panel completed a public review of the concept proposed for the disposal of Canada's nuclear fuel waste within plutonic crystalline rock of the Canadian Shield. Safety of the geologic disposal concept was evaluated in two Integrated Performance-assessments submitted to the Panel: the environmental Impact Statement Case Study (EIS) and the Second Case Study (SCS). These assessments examined the behaviour of two hypothetical disposal systems with different engineered designs and geosphere properties. The properties of the geosphere were based primarily on geoscience research and site characterization activities initiated by Atomic Energy Canada Limited in 1981. An important objective in the Panel's mandate was to review the safety and scientific acceptability of the geological disposal concept. The review process was broad and included submissions by a Panel-appointed Scientific Review Group, federal regulatory agencies, learned geoscience bodies and advocacy groups. While general agreement existed amongst most technical reviewers that the geologic disposal concept was safe and viable, there was also dissatisfaction with the sufficiency and adequacy of the arguments. This paper examines four geoscience issues that arose during the Panel review, particularly as they affect the application of geosphere Performance Assessment (PA) methodologies used in evaluating concept safety. The issues deal with PA model verification, methods to deal with conceptual flow model uncertainty, the connection between detailed geosphere models and the integrated performance-assessment models, and PA documentation. A goal of this paper is to gain a better understanding of the expectations held by external reviewers of the EIS and SCS, and the elements that most affected confidence in predicted repository performance.