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[en] Criteria for selecting from alternative measures of plant information have been derived by information theory and the expected-value model of decision theory. Two criteria derived by information theory are minimum ''uncertainty'' of judgement of plant states, and maximum ''surprise'' of human operators. Two criteria derived by decision theory are maximum expected reward to operators, and maximum ratio of the maximum and next-to-maximum expected rewards. These four criteria have been evaluated experimentally in application to human monitoring problems of three ''plants'': an abstract laboratory exercise, a small research reactor, and a conventional nuclear power plant (high-fidelity training simulator). The results show that the criteria derived by decision theory are superior to the others from the viewpoint of correct rate of human subjects' judgement

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[en] A method has been developed to optimally and automatically determine the adjustable parameters of the boiling water reactor three-dimensional core simulator FLARE. The steepest gradient method is adopted for the optimization. The parameters are adjusted to best fit the operating data on power distribution measured by traversing in-core probes (TIP). The average error in the calculated TIP readings normalized by the core average is 0.053 at the rated power. The k-infinity correction term has also been derived theoretically to reduce the relatively large error in the calculated TIP readings near the tips of control rods, which is induced by the coarseness of mesh points. By introducing this correction, the average error decreases to 0.047. The void-quality relation is recognized as a function of coolant flow rate. The relation is estimated to fit the measured distributions of TIP reading at the partial power states

[en] A core management system by data communication has been designed and proposed for more efficient operation of boiling water reactor (BWR) plants by faster transmission and centralized management of information. The system comprises three kinds f computers: a process computer for monitoring purposes at the reactor site, a center computer for administration purposes at the head office, and a large scientific computer for planning and evaluation purposes. The process and the large computers are connected to the center computer by a data transmission line. To demonstrate the feasibility of such a system, the operating history evaluation system, which is one of the subsystems of the core management system, has been developed along the above concept. Application to the evaluation of the operating history of a commercial BWR shows a great deal of merit. Quick response and a significant manpower reduction can be expected by data communication and minimized intervention of human labor. Visual display is also found to be very useful in understanding the core characteristics

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