Long-term operation of nuclear steam generators can result in the occurrence of clogging, a deposition phenomenon that may increase the risk of mechanical and vibration loadings on tube bundles and internal structures as well as potentially affecting their response to hypothetical accidental transients. To manage and prevent this issue, a robust maintenance program that requires a fine understanding of the underlying physics is essential. This study focuses on the utilization of a clogging simulation code developed by EDF R&D. This numerical tool employs specific physical models to simulate the kinetics of clogging and generates time dependent clogging rate profiles for particular steam generators. However, certain parameters in this code are subject to uncertainties. To address these uncertainties, Monte Carlo simulations are conducted to assess the distribution of the clogging rate. Subsequently, polynomial chaos expansions are used in order to build a metamodel while time-dependent Sobol’ indices are computed to understand the impact of the random input parameters throughout the whole operating time. Comparisons are made with a previous published study and additional Hilbert-Schmidt independence criterion sensitivity indices are computed. Key input-output dependencies are exhibited in the different chemical conditionings and new behavior patterns in high-pH regimes are uncovered by the sensitivity analysis. These findings contribute to a better understanding of the clogging phenomenon while opening future lines of modeling research and helping in robustifying maintenance planning.

中文翻译：

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蒸汽发生器多物理长期堵塞模型的灵敏度分析

核蒸汽发生器的长期运行可能会导致堵塞，这是一种沉积现象，可能会增加管束和内部结构上的机械和振动载荷的风险，并可能影响它们对假设的意外瞬态的响应。为了管理和防止这个问题，需要深入了解底层物理原理的强大维护计划至关重要。本研究重点关注 EDF R&D 开发的堵塞模拟代码的使用。该数值工具采用特定的物理模型来模拟堵塞动力学，并为特定蒸汽发生器生成与时间相关的堵塞率曲线。但是，此代码中的某些参数存在不确定性。为了解决这些不确定性，进行蒙特卡罗模拟来评估堵塞率的分布。随后，使用多项式混沌展开来构建元模型，同时计算与时间相关的 Sobol 指数，以了解随机输入参数在整个操作时间内的影响。与之前发表的研究进行比较，并计算附加的希尔伯特-施密特独立性标准敏感性指数。关键的输入输出依赖性在不同的化学条件下表现出来，并且通过敏感性分析揭示了高 pH 条件下的新行为模式。这些发现有助于更好地理解堵塞现象，同时开辟未来的建模研究路线并帮助完善维护计划。