An Analysis on Possible Effects of Instrument Faults on Situation Assessment of Nuclear Power Plant Operators

Recently, the effects of instrument faults on the situation assessment of nuclear power plant (NPP) operators have received a lot of attention. In ATHEANA [1], which is a second generation human reliability analysis (HRA) method developed by U. S. Nuclear Regulatory Commission (NRC), many statements emphasizing the importance of instrument faults on the development of wrong situation models can be found in many places. The approach for analyzing errors-ofcommissions proposed by Kim et al.[2] also analyze the possibilities of NPP operators being misled to develop wrong situation models due to instrument faults. But, as mentioned in ATHEANA, there has been very little consideration of how instrument faults will affect the ability of the operators to understand the conditions within the plant and act appropriately. In this paper, we provide an analysis results on the possible effects of instrument faults on the situation assessment of NPP operators from the simulation results of Compact Nuclear Simulator (CNS), which is a small simulator for Westinghouse 900MWe Pressurized Water Reactor (PWR) plants.