A framework for evaluating the effects of maintenance-related human errors in nuclear power plants

This paper proposes a framework for estimating the qualitative and quantitative consequences of human errors that occur during maintenance tasks involving the balance of plant in nuclear power plants. One of the remedies for unexpected reactor shutdowns may be a methodical tool designed to warn potential hazards arising from given maintenance tasks, taking into account human error modes in a proactive manner, in terms of risk and/or loss of electrical power. The entire framework that we established is composed of four components: (1) the human-error analyzer to connect possible failure modes resulting from human errors with other estimators, (2) the frequency estimator to quantify the occurrence of maintenance-related failure modes, (3) the risk estimator to determine minimal cutsets and to compute the variation of the core damage frequency using the fault tree analysis and turbine cycle simulation, and (4) the derate estimator to determine the electrical power loss under abnormal plant configurations caused by human error. The final result is characterized by a cost metric that can be used for decision-making possibly resulting in revisions of procedures, or task modifications. This paper also discusses case studies to illustrate the feasibility of the proposed framework.