基于局部法的反应堆压力容器多裂纹概率评定方法研究

The probabilistic fracture mechanics analysis based on macroscopic fracture theory is applied to perform the probabilistic assessment for reactor pressure vessel (RPV) with defects. One single crack is limited in this analysis. However, some cracks may be existent together in RPV. The stochastic distribution of cracks and their interference effect are neglected to calculate the failure probability. A probabilistic assessment method on local approach for RPV with multi-cracks is proposed. Firstly, a local model for multi-cracks on plastic zone is developed, with the consideration of interference effect. The uncertainty of the model parameters is investigated, to reveal the influence mechanism of randomness in material fracture resistance. Then, a Weibull stress model for multi-cracks is proposed to calculate the drive force under the combine of temperature difference and mechanical loads. The stochastic distribution of cracks is introduced in this model. Therefore, the probability distribution of Weibull stress is derived. At last, a typical pressurized thermal shock event in nuclear power plant is studied, and the conditional failure probability of RPV with multi-cracks is obtained. The probabilistic assessment method for RPV with multi-cracks is proposed on the system research of multi-cracks stochastic distribution, the model parameters, Weibull stress and their randomness. The difficulty of probabilistic assessment for RPV with multi-cracks can be effectively solved. At the same time, this work will lay a foundation for RPV assessment criterion on risk. It is of great significance to ensure the structure integrity of RPV with multi-cracks.

反应堆压力容器(RPV)中缺陷概率评定仍限于单一主裂纹的宏观概率断裂力学分析，忽略了RPV中多裂纹的随机分布及其干涉效应对RPV失效的影响。本课题利用细观断裂力学模型建立基于局部法的多裂纹概率评定方法。考虑多裂纹干涉效应，发展基于塑性区连通域的多裂纹局部法模型，探索多裂纹局部法模型参数的不确定性，揭示结构断裂强度随机性的影响机理。研究温差与机械载荷联合作用下多裂纹Weibull应力模型，建立考虑裂纹分布的RPV多裂纹概率模型，推导出多裂纹断裂推动力及其随机性。在此基础上，对典型承压热冲击工况进行分析，获得含多裂纹的RPV条件失效概率。多裂纹概率评定方法是在系统研究多裂纹分布、多裂纹局部法参量以及Weibull应力等随机性的基础上提出的，可有效解决多裂纹随机共存时RPV的概率评定难点，为构建基于风险的RPV评定准则奠定基础，对保证RPV的结构完整性有重要意义。

受制造与检测技术的制约，反应堆压力容器(Reactor Pressure Vessels, RPV)中的一些缺陷在制造时未被检出。随着检测精度的提高，一些裂纹直到服役后才被检出，且可能伴随着多个裂纹共存。因此，合理描述缺陷的随机性并对其进行结构完整性评定对保证核电厂的安全具有重要意义。传统的评定方法忽略了裂纹的分布随机性对RPV失效的影响，不能直接对应核安全的概率要求。对此，项目基于局部法模型建立了含缺陷RPV的概率评定方法，符合基于风险的核安全发展趋势，可为构建满足核安全概率要求的RPV评定准则提供技术支撑。. 项目针对含缺陷RPV，建立了考虑面内外拘束效应的局部法模型，探索了局部法模型参数的不确定性，降低主观不确定性，提高模型预测精度。基于宏观断裂力学参数推导出了I-II复合型裂纹的Weibull应力解析计算式。基于发展的Weibull应力模型，利用改进的边界层模型有效地预测J-T应力场下的Weibull应力，分析了PTS条件下的RPV接管拐角裂纹失效概率。对高强钢材料性能开展了材料的疲劳断裂性能研究，为项目开展断裂力学分析提供了基础数据支撑。在项目研究基础上，将核承压设备的概率评定方法推广到常规压力容器概率分析应用。. 项目已发表SCI论文9篇。项目成果可为核承压设备的概率评定提供技术支撑，正在积极推进项目成果的标准化应用。同时，对非核容器的设计评定也具有一定的参考价值。