Recent activities in the field of NPP I&C and human factor

In the field of nuclear power plant (NPP) instrumentation and control (I&C), the studies on technologies to validate the reliability of complex systems and to improve system safety by utilizing computers have been progressed as the digitalized systems and computers have been introduced into advanced reactors. Real-time computer systems become indispensable to control modern NPP and their system architecture is important to validate their reliability. For example, several bus architectures of fault-tolerant computer systems have been compared from the viewpoint of reliability [1]. Modern advanced digital protection systems employ various fault-tolerant techniques to improve their reliability and the modeling method for their evaluation has been proposed [2].

As advanced types of reactors have been developed, the techniques of their I&C have been also progressed. High temperature engineering test reactor (HTTR), which is a test reactor to realize commercial high-temperature gas reactor, has been developed by Japan Atomic Energy Agency (JAEA) and they achieved 50-day operation at 950 °C in 2010. The detailed procedures and results have been reported [3,4], and its future test plan for the reactor stability and control against thermal load fluctuation have been proposed [5]. And, core protection and monitoring system of SMART, which is a system-integrated modular advanced reactor with 30 MW thermal power under development in Korea Atomic Energy Research Institute (KAERI), has been also reported [6].

Related to the accident in Fukushima Daiichi NPP, the techniques to survey the locations and conditions of fuel debris inside reactor vessel have been studied especially in Japan. For example, self-power gamma detectors, which have only a few millimeters diameter, were developed [7]. Radiation-resistant optical fiber was also developed for the observation and laser spectroscopy under high radiation dose [8].

Human factor research studies for advanced main control room (AMCR) have been also active for this several years. Although AMCR offers various operation support systems utilizing computers, large screen displays and individual terminals, human reliability analysis in emergency situations is necessary from the viewpoint of human factors. Comparing with conventional main control room, fault diagnosis strategy or human error mode in AMCR may be different and their research studies have being progressed and reported [9–12].

In human factor research studies of NPP, most of them focus on operators’ behaviors in emergency situations, and subject experiments have been often conducted with NPP simulators. Since several decades past after starting commercial operation of NPP, empirical studies on human factor have appeared recently [13–15]. For example, human error probabilities (HEPs) have been evaluated from the operation experience of German NPPs [13]. Empirical investigation was conducted to compare operators’ workloads in AMCR with those of conventional control room using cognitive-communicative-operative activity (COCOA) framework [14]. The influence of task complexity on HEP was studied with TAsk COMplexity (TACOM) measure and empirical evidence on HEPs [15].

As shown above, the recent advancement of Information and Communication Technology (ICT) and the development of new type reactor have been promoting I&C and human factor research studies in various nuclear fields.