Protection against turbine missiles in HPR1000

Turbine missiles may cause damage to the safety important items of nuclear power plant, which are normally evaluated by probabilistic analysis methods. The failure probability of essential items is analyzed, and the corresponding protection design is provided in HPR1000. This study discusses the two modes of missile generation mechanisms during the probabilistic analysis, i.e. the rotor material failure due to stress corrosion cracking, and the failure of the overspeed protection system. Besides, modeling of the strike probability is accomplished, combining with the location of the turbine unit in the nuclear island, using characteristic parameters and conservative assumptions of turbine missiles. Based on the calculation results, the plant layout and protection design can be directed, to comply with the regulation and guidance requirement of < 10' -' 7/unit · year, which reduces the input cost due to design change. (authors)