Human reliability modeling for the Next Generation System Code

This paper derives the human reliability model requirements for the Next Generation system Code which will be utilized to determine risk-informed safety margins for nuclear power plants through dynamic probabilistic risk analysis. The proposed model is flexible, with the facility to apply a coarse-grain or a fine-grain structure based on the desired resolution level. The varying resolution is achieved by employing human reliability analysis methods with the demonstrated capability of handling human errors that occur during the execution of procedural activities for the coarse-grain structure and the advanced cognitive IDA/IDAC method for the fine-grain structure. The paper proposes improvements to the existing IDA/IDAC model to incorporate functionalities demanded by the NGSC. The improvements are derived for four modules of IDA/IDAC. A Bayesian belief network is constructed for the performance-shaping factors and the conditional probability for existence of each factor is computed from data collected from aviation and nuclear accidents. The influence of the performance-shaping factors on the strategy-selection process of the operator is also depicted. A foundation is laid for the development of mental models with a focus on NPP operation. The research lists the modifications/additions required for the IDA/IDAC method to enable the incorporation of Human Reliability Analysis (HRA) into the Next Generation System Code. (C) 2012 Published by Elsevier Ltd.