After Fukushima, the design of nuclear power plants to cope with beyond design basis accidents and severe accidents is urgently needed to be improved. That means the previous design envelope scope needs to be optimized and extended. Some accident conditions which may be less probable but still with obvious risk should be enveloped into advanced nuclear power plant design consideration. As an effective tool to evaluate the progression of various accidents and corresponding management measures, probabilistic safety analysis (PSA) can be used to evaluate the vulnerabilities of the plants' safety during different accident scenarios. In this paper, firstly both level 1 and level 2 PSA modeling are carried out for Fuqing Phase I nuclear power plant. According to the PSA calculation results of this typical generation II plant designed in China, a series of beyond design basis accident and severe accident scenarios may cause unacceptable core damage and radiological release frequencies that will violate the requirement of the newly-issued design safety code HAF102 in China. For China's newly-designed evolutionary type advanced PWR plant, in order to achieve the high design safety level stated in HAF102, these non-negligible scenarios should be enveloped into plant's design basis. By introducing these conditions into new design envelope scope, finally a series corresponding new safety design features are suggested for China's advanced nuclear power plant.
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