Norihiko Handa

A Method of State Transition Analysis Under System Interactions: An Analysis of a Shutdown Heat Removal System

Taking the decay heat removal system of a liquid metal fast breeder reactor (LMFBR) as an example, a new reliability analysis method has been developed that can estimate how a failure occurring in a subsystem of a redundant system proliferates to another subsystem and how the independence of the redundant system is gradually lost. The Monte Carlo method is employed in the state transition representation. Environment changes evaluated from physical parameters, which correspond to failure time and to time- and sequence-dependent failure rates, are used to evaluate the stress-strength model. The failure rates derived are used to identify subsequent sequences. The investigation of the interaction between the system and the pipe in the decay heat removal system has revealed that the influence is small under conditions set for this study.

Study on Ultra-Long Life, Small U-ZR Metallic Fuelled Core With Burnable Poison

A conceptual design for a 50MWe sodium cooled, U-Pu-Zr metallic fuelled, fast reactor core, which aims at a core lifetime of 30 years, has been performed [1]. As for the compensation for a large burn-up reactivity through 30 years, an axially movable reflector, which is located around the core, carries the major part of it and a burnable poison does the rest. This concept has achieved not only a long core lifetime but also a high discharged burn-up. On this study, a conceptual design for a small fast reactor loading U-Zr metallic fuelled core instead of U-Pu-Zr fuelled core has been conducted, based on the original core arrangement of 4S reactor [2]. Within the range of this study including safety requirements, adopting the burnable poison would be effective to construct a core concept that achieves both a long lifetime and a high discharged burn-up.Copyright

A new approach to simplified liquid-metal fast breeder reactor plant design

A plant design simplification method is discussed. The method takes advantage of features found in moderately sized plants in order to increase fast breeder reactor deployment under uncertain load growth projection conditions. Some new and simplified design features for the plant main body are examined and determined to be applicable to plant overall design.

Probabilistic fracture evaluation of a fast breeder reactor cover

The structural reliability of a fast breeder reactor cover was evaluated using probabilistic fracture mechanics. The effects of important factors (initial crack distribution, crack detection level, crack growth rate, incidence of events such as earthquakes, in-service inspection for cracks, weld toughness, residual stresses, and environmental effects) on the reliability of structures were estimated, and methods for maintaining proper reliability were studied. It was found that the probability of the reactor losing its function is --10/sup -8/ in the terminal stage of the plant lifetime, even when the most conservative initial crack distribution and crack detection level are assumed. However, the prerequisite of such a condition is the use of appropriate leak monitors or proper atmospheric control. It was also confirmed that the degree of improvement in reliability through in-service crack detection, which was considered to be important, is not necessarily significant for the reactor cover.