Margin Analysis of Conventional Island Under Beyond Design Basis External Flooding Scenario for NPP

Abstract

Since the external flooding caused by the earthquake and tsunami at Fukushima Daiichi nuclear power plant in Japan, the waterproofing ability of the nuclear power plants, in operation or under construction, has attracted widespread attention from nuclear safety authorities and the public all over the world. While less attention was paid to the conventional island area. The failure of systems and components arranged in the conventional island may lead to the turbine out of the normal operation and impact the operation reliability of the unit, which would influence the generating capacity and availability of the power plant. In this paper, it is selected the combination of “design basis flood (DBF) with the rainfall of a frequency of 10-3/yr” as the analyzed scenario. According to the site characteristics, the variation of external flooding depth on the site over time was calculated under this scenario, the path of external flooding was determined, and the amount of the flooding water, the conventional island ultimately invaded, was calculated. For the availability of the power plant, the corresponding improvement measures were put forward to improve the waterproofing capacity of the plant, which can be a significant reference to the nuclear power plants in our country.