Safety assessments for geologic radioactive waste disposal systems involve risk assessments that
cover many topics within a wide range of technical disciplines. Priorities should be set for
investigating these topics to ensure that the most important aspects of the repository behavior are
well understood. This paper presents a decision-analysis framework designed to support such risk
assessments by identifying important issues upon which to focus technical work. Key attributes of
this framework are (i) an analytical procedure that integrates risk perception with technical
evidence, (ii) an algorithm that does not involve execution of a mathematical simulation model,
and (iii) a set of metrics that indicate the important technical issues for the risk assessments. A
demonstration of the decision-analysis framework on a hypothetical geologic repository highlights
the joint impact of perception and evidence on decisions that inform priorities for advancing
technical work and building confidence in projections of future behavior for radioactive waste
disposal systems. Potential applications to other systems analyses are discussed.
