ABSTRACT
This chapter discusses some of the main issues in problem definition in the human reliability assessment (HRA) process. There are two fundamental issues that need to be addressed in any practical HRA concerning its nature and scope, and these can best be put as the following questions: Should the HRA be quantitative or qualitative in nature? How far should the scope of an HRA go? The HRA analyst wants to make sure that he or she does not underestimate, nor, on the other hand, significantly overestimate, the impact of human error on system risk levels or performance. Once a system's level of vulnerability has been addressed, the next main constraint to the HRA will come from Probabilistic Safety Analysis (PSA) considerations: whether the HRA is part of a PSA; whether the HRA will be PSA-driven; whether risk-reduction measures may be required; what criteria the PSA is assessing against; and whether prior PSAs have been carried out.
