Designing risk-management strategies for critical engineering systems

Effective management of the tradeoff between productivity and safety is a challenge in many industries that operate critical engineering systems such as nuclear power plants or offshore oil platforms. The objective of this paper is to link risk-management strategies to a system's safety and productivity over its lifetime. These strategies involve decisions that affect the physical system both directly and indirectly though the performance of the personnel that design, construct, or operate it. The problem is thus to link the different components of such risk-management strategies to human and system performance. In this paper, we present the basis of a decision support framework for the design and assessment of different risk-management strategies in risk-critical systems. First we discuss the inherent difficulty in balancing productivity and safety in the short and the long term and the different components of a risk-management strategy. We present a model involving both production failures and catastrophic failures as a function of strategic alternatives. This model is based on a probabilistic and dynamic risk analysis of a system, linking different aspects of risk-management strategies to specific characteristics of the physical system. We show how this model, coupled with explicit value judgments, can be used to design optimal strategies, e.g., to balance initial costs, long-term operations and maintenance costs, and the potential costs of catastrophic failures. To illustrate the concepts we use the case of the maintenance of a corporate airplane.