Integrated functional modeling method for NPP plant DiD risk monitor and its application for conventional PWR

The development of a new risk monitor system is introduced in this paper, which can be applied not only to severe accident prevention in daily operation but also to serve as to mitigate the radiological hazard just after severe accident happens and long term management of post-severe accident consequences. The summary of the fundamental method is given on how to configure the Plant Defense in-Depth (DiD) Risk Monitor by object-oriented software system based on functional modeling approach. Following the authors' preceding preliminary study for AP1000, the way of realizing the proposed method of configuring the plant DiD risk monitor was investigated for a safety-enhanced Japanese PWR design to meet with the tight anti-severe accident requirements set by national regulation in Japan after Fukushima Daiichi accident. The result of this example practice of the presented preliminary study for Japanese PWR was for the level 4 of the DiD in case of beyond design basis accident, that is, loss of all AC power + RCP seal LOCA, against the former case of AP1000 for level 3 DiD in case of large LOCA. (author)