Subjective bias in PRA - the role of judgement in the selection of plant modeling input data for establishing safety goals

The sources of the uncertainties are generally accepted as modeling deficiencies, lack of completeness in the analysis and the input data deficiencies. The role of judgement in selecting input data for establishing safety goals will be discussed. As an example, a safety goal for unacceptable radioactivity release will be considered. Two analysts are discussing the introduction of an emergency service water system, applying a different way of engineering judgement. Using PRA combined with safety goals as a decision-making tool it could have an important influence on the design and the costs of the plant. The suitability of the methodology has to be generally accepted before it will be established as a regulatory requirement. (orig.)