Structural Vulnerability Analysis Of AP1000 Nuclear Island Under Sequential Earthquake

AP1000 nuclear power station is the advanced nuclear power reactor in China.It has the advantages of high security and simple operation,and the ACP1000 nuclear power plant in China is developed by using the advanced design concept of AP1000.The structure of AP1000 nuclear island is complex as a whole,and its model volume is large.The maximum damage value of the whole structure can not accurately reflect the damage situation of all parts of the structure of the nuclear power plant.However,there are few literatures about the damage of the structure of AP1000 nuclear island under the strong main aftershock sequence earthquake.Therefore,this paper takes the AP1000 nuclear island structure as the research object,first analyzes its dynamic response under strong main aftershock sequence and single main earthquake;then,in order to study the damage development of each local area of the nuclear island structure,it uses the partition method to divide the nuclear island structure,and analyzes the average value and maximum value of the damage of each area,so as to get the reasonable damage of each area mode.Finally,the damage vulnerability analysis is carried out for each region of the nuclear island to quantify the failure probability of the structure under the strong main aftershock sequence and single main earthquake.The main research work and conclusions are as follows:1.The peak acceleration,peak displacement and cumulative plastic strain of the two nuclear island models with and without gate openings are compared.The results show that the peak acceleration,peak displacement and cumulative plastic strain of the nuclear island structure with gate opening are higher than those without gate opening,and the gate opening aggravates the dynamic response and damage degree of the nuclear island structure.2.The dynamic response of AP1000 nuclear island structure under strong main aftershock sequence and single main earthquake is studied.The residual displacement,maximum equivalent stress and equivalent plastic strain are compared.The results show that the residual displacement and the equivalent plastic strain of the joint under the main aftershock sequence are larger than that of the nuclear island structure under the single main earthquake,the aftershock aggravates the damage degree of the shield building,and the containment is always in the safe elastic stage under the strong earthquake.3.Based on the concept of structural zoning,the damage average value and maximum value of each region are compared,and the nuclear island structure is divided carefully,and the damage development of the local region of the nuclear island structure is studied.The results show that the damage degree of RS area at the bottom of the nuclear island structure is relatively small,and the maximum damage value is used to reflect the damage situation;the average damage value of RC area along the circular direction can reflect the damage situation well,but the more precise average damage value within 0.3m along the circular direction is used at the gate opening with stress concentration.4.Based on the incremental dynamic analysis(IDA)method,the vulnerability analysis of each region is carried out,and the failure probability of each region of AP1000 nuclear island structure under the strong main aftershock sequence earthquake and single main earthquake is compared and analyzed.The results show that the damage probability of each state in RS region is less than that in RC region,and the damage probability of RC-2 and RC-4 regions at the gate opening is the largest;the damage probability of each region under the main aftershock is greater than that under the single main shock,and the effect of aftershock intensifies the exceeding probability of structural damage.