The US-APWR, currently under Design Certification review by the U.S. Nuclear Regulatory Commission, is a four loop evolutionary pressurized water reactor with a four train active safety system applied by Mitsubishi Heavy Industries. The digital Instrumentation and Control (I&C) System and Human Systems Interface (HSI) system are to be applied to the US-APWR. This design is currently being applied to the latest Japanese PWR plant and to nuclear power plant I&C modernization program in Japan. The US-APWR digital I&C and HSI system (HSIS) utilizes computerized systems, including computer-based procedures and alarm prioritization, relying principally on an HSIS with soft controls, console based visual display units (VDUs) and a large, heads up, overview display panel. Conventional hard-wired controls are limited to system level manual actions and a Diverse Actuation System (DAS). The overall design philosophy of the US-APWR is based on the concept that operator performance will be enhanced through the integration of safety and non-safety display and control systems in a robust digital environment. This philosophy is augmented, for diversity, by the application of independent safety soft displays and controls. In addition, non-digital diverse automatic and manual actuation system is introduced. As with all the advanced designs, the digital systems open as many questions as they answer. To address these new questions, for an eight week period during the months of July and August 2008, an extensive verification and validation (V&V) program was completed with the objective of assessing US operators’ performance in this digital design environment. (Robert E. Hall et al., 2008, “US-APWR Human Systems Interface System V&V Results: Impact on Digital I&C Design”, 17th International Conference on Nuclear Engineering, ICONE17-75176) [1] Over this time period, U.S. operating crews were subjected to exercise in Mitsubishi dynamic simulator. To follow up above mentioned V&V activities, additional test during the months of this spring in 2009 has been carried out to resolve human engineering discrepancies (HEDs) induced from the previous evaluation and the participants’ comments and performance. Subjective and objective data were collected on each crew for each scenario and an extensive convergent measures analysis was performed, resulting in the identification of both specific design as well as generic conclusions. This paper discusses the digital HSIS of the US-APWR design, the V&V program data collection and analysis, and the study results related to the ongoing discussion of the impacts of digital systems on human performance, such as workload, navigation, situation awareness, operator training and licensing.

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