Reliability of Large Technological Systems

Codes and regulations regarding large technological systems of growing complexity should take into account the increasingly sophisticated analysis tools that have been and are being developed in order to judge the reliability or risk associated with complex technology. PSA (Probabilistic Safety Assessment) as an extension of system reliability analysis is a powerful means of supporting this aim by providing an integrative and quantitative information basis for decision making. PSA has to date been successfully applied in various branches of technology. Experience has shown that observed time dependencies agree well with assumed component failure rate models and that CMF (Common Mode Failure) assessment is an essential part of PSA. Importance calculations are shown to provide valuable guidance in the search of improved system reliability. Model uncertainties and operator performance are increasingly receiving attention and the importance of interaction between system and structural reliability experts is stressed. Four examples from various industrial branches are given as illustrations of recent efforts in the field of PSA.