Availability analysis of nuclear power plant system with the consideration of logical loop structures

MATSUOKA Takeshi^{1, 2}

1. Mechanical Systems Engineering, Department of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya City, 321-8585 Japan (mats@cc.utsunomiya-u.ac.jp)
2. College of Nuclear Science and Technology, Harbin Engineering University No.145-1, Nantong Street, Nangang District, Harbin, Heilongjiang Province, 150001 China

Abstract: Nuclear power plants have logical loop structures in their system configuration. The typical example is a power source system, that is, a nuclear plant generates electricity and it is used for the operation of pumps in the plant. For the reliability or availability analysis of nuclear power plants, it is necessary to treat accurately logical loop structures. Authors have proposed an exact method for solving logical loop structure in reliability analysis, and generalized method has recently been presented. A nuclear power plant system is taken up and essential parts of logical loop structures are modeled into relatively simple form. The procedure to solve a loop structure is shown in which the proposed generalized method is applied, and availability of the system with loop structure is accurately solved. The analysis results indicate that reconsideration of present plant operating procedure should be made for the increase of safety of nuclear power plant in case of "Loss of offsite power" incident. The analysis results also show an important role of loop structures for maintaining the overall system availability. The analysis procedure is also useful in effectively designing high reliable systems.
Keyword: logical loop; availability analysis; reliability analysis; safety of nuclear power plant