强震及内压连续作用下核电厂安全壳破坏机制与全寿命易损性研究

Under strong earthquakes, the containment and internal equipment of nuclear power plant may be damaged at the same time, and the failure of internal equipment will inevitably cause the containment to bear internal pressure. The failure mechanism of containment under strong earthquake and successive internal pressure is worthy of further study. By means of combining numerical simulation, experimental research, and theoretical analysis methods in this project, the pseudo-dynamic test and continuous internal pressure test of containment is conducted as the entry point and a reliable numerical modeling method is proposed. The influence rule of the continuous action of different intensity, different type earthquakes and internal pressure on the failure mechanism of containment is revealed; On this basis, fully considering the aging of concrete, corrosion of steel bars and loss of prestress, the finite element model of containment at different service periods is established. Making full use of a large number of ground motions, the relationship between various parameters of strong ground motion and reasonable response control index of containment is studied systematically. The expression of damage potential of ground motion for containment is proposed. The performance index of life-cycle based seismic safety for the containment is established. The life-cycle based fragility evaluation is realized and the time-varying seismic capacity of containment with high confidence and low probability of failure is determined. This project will provide a reference for the revision of seismic design code for nuclear power plants, and it is of great significance in ensuring the seismic safety, mitigating earthquake disasters and extending the life of nuclear power plants.

强震作用下核电厂安全壳与内部设备可能同时发生损伤，内部设备失效必然引起安全壳承受内部压力，安全壳在强震及内压先后作用下的破坏机制值得深入研究。本项目将采用数值模拟、试验研究与理论分析相结合的方法，以核电厂安全壳的拟动力试验及连续内压试验为切入点，提出可靠的数值建模方法，揭示不同强度、不同类型地震及内压连续作用对破坏机制和失效模式的影响规律；在此基础上，综合考虑混凝土老化，钢筋腐蚀及预应力损失等因素，建立不同服役龄期的安全壳有限元模型，充分利用大量地震动，系统研究强地震动参数与结构合理反应控制指标的关系，提出针对安全壳结构的地震动潜在破坏势表达，建立安全壳全寿命抗震安全性的性能指标，实现全寿命易损性评估方法，确定安全壳时变高裕度低失效概率抗震能力。本项目将为核电厂抗震设计规范的修订提供参考，对保障核电厂的地震安全、减轻地震灾害及延寿决策具有重要的意义。

本项目针对核电厂安全壳强震-内压连续作用下的安全性能进行了全面研究，建立了结构可靠性好、实用性强的安全壳结构有限元数值建模和分析方法，研究了地震作用、内压作用及强震-内压连续作用下安全壳结构的反应性态，发现随地震动强度的增加而增加，不同类型地震动下安全壳混凝土贯穿裂缝面积均值比从5.41%（2SSE）显著增加到45.79%（5SSE）、安全壳钢衬里屈服面积均值比从1.23%（3SSE）显著增加到26.17%（5SSE）。内压增长至超设计内压后，伴随着混凝土裂缝的全面演化，钢衬里和预应力钢束连续屈服，造成安全壳最终倒塌。当地震动强度达到4SSE时，核安全壳结构的损伤耗散迅速增加，损伤程度急剧加重，承压性能受到显著影响。考虑核电厂安全壳结构和次级系统，项目利用机器学习方构建多元IMs地震潜在破坏势参数，同时提出机器学习驱动的概率地震需求模型框架，并根据相应的评价指标来评估EDP预测响应的效率，确定了最优精度模型，发现机器学习方法能极大改善单维或矢量地震动参数线性组合的潜在破坏势参数构建的传统概率地震需求模型。重点考察了预应力损失对安全壳长期性能的影响，发现考虑5年预应力损失时，安全壳在内压作用下的损伤表现最为显著，通过5年的预应力损失可以较好地预测和评估安全壳在不断增长的预应力损失作用下的损伤表现。本项目将为核电厂抗震设计规范的修订提供参考，对保障核电厂的地震安全、减轻地震灾害及延寿决策具有重要的意义。