面向严重事故管理的系统分析程序-自动机器学习模型在线耦合框架

System Analysis Code-AutoML Model Online Coupling Framework for Severe Accident Management

  • 摘要: 现有热工水力系统分析程序通常依赖经验或半经验关系式计算传热、传质、相变等局部物理过程的关键物理模型系数,但在高压、低流速、混合对流及含不凝性气体等复杂工况下,其预测精度和适用范围可能受到限制。为提高系统程序对局部物理过程的模拟能力,本文提出一种系统分析程序-自动机器学习(AutoML)模型耦合框架。该框架保留系统分析程序对质量、能量和动量守恒方程的求解能力,利用AutoML模型预测局部过程所需的关键物理模型系数,并通过通用接口程序实现时间步推进、状态参数提取、单位转换、特征构造、模型调用、结果回传和异常处理。以含不凝性气体条件下的冷凝传热系数预测为例,本文选取作者前期已建立并验证的自动机器学习模型作为验证对象,实现其与系统分析程序MOSAP的在线耦合。结果表明,该框架能够稳定调用AutoML模型,并将预测结果返回系统程序参与后续热工水力计算。系统分析程序-AutoML在线耦合框架可为复杂事故工况下关键模型扩展、预测精度提升和不确定性分析提供一种潜在途径。

     

    Abstract: Existing thermal-hydraulic system analysis codes usually rely on empirical correlations to calculate key physical model parameters related to heat transfer, mass transfer, and phase change. However, under complex conditions that deviate from the original experimental fitting ranges, such as high pressure, low flow rate, mixed convection, and the presence of non-condensable gases, the predictive accuracy and applicability of conventional empirical correlations may be limited. To improve the predictive capability for key model parameters in system analysis codes, this study proposed a coupling framework between a system analysis code and automated machine learning. In this framework, the system analysis code solved the mass, energy, and momentum conservation equations to obtain thermal-hydraulic state parameters. The automated machine learning model was used to predict key model coefficients required for local physical processes such as heat and mass transfer. And the general-purpose interface program was responsible for invoking both the system analysis code and the automated machine learning model, coordinating the time advancement, and transferring variables among the thermal-hydraulic state parameters, key physical model coefficients, and the input and output variables of the machine learning model. Taking the prediction of condensation heat transfer coefficient under conditions with non-condensable gases as an example, the previously developed and validated AutoGluon model for condensation heat transfer coefficient prediction was selected as the validation object. Through the general-purpose interface program, online coupling between this model and the MOSAP system analysis code was realized. The results show that the proposed coupling framework enables stable and efficient invocation of the system analysis code and the automated machine learning model during transient time-step advancement. This method provides a feasible pathway for model extension and accuracy improvement of system analysis codes under complex accident conditions, and offers methodological support for thermal-hydraulic state prediction, model uncertainty analysis, and accident mitigation strategy evaluation in severe accident management.

     

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