高温气冷堆全耦合系统直接联立求解的方法研究和程序开发

Simultaneous Solution for Whole High Temperature Gas-cooled Reactor Coupled System:Method Research and Code Development

反应堆耦合计算是对现有反应堆各领域数值技术的融合、集成和提升,完整的反应堆核电站系统同时具有多种耦合机制,是一个超大规模非线性强耦合系统,以JFNK/NK为代表的直接联立方法是极具潜力的发展方向。本文在综述国内外反应堆耦合计算研究的基础上,介绍了清华大学核能与新能源技术研究院在高温气冷堆核电站全耦合直接联立求解方法及程序开发方面的研究工作。针对高温气冷堆多物理、多尺度、多部件、多回路、多模块的耦合特点,首次提出了非线性消去直接联立方法等关键技术,研发可以描述多层级耦合结构的统一耦合平台框架,已形成多个中间版本的程序。

The numerical calculation for nuclear reactor coupled system is the fusion,integration and upgrade of the existing numerical technologies in various related fields.Generally,the whole nuclear power plant has several different coupling mechanisms inherently,such as the multi-physics coupling,multi-scale coupling and multi-system coupling,which is an ultra-large-scale strong nonlinear coupling system.Moreover,each coupling mechanism has its own mathematic features.The combination of different coupling mechanisms is such complicated,which is still an open issue for nuclear engineering community.Simultaneous solution methods,such as Jacobian-free Newton Krylov(JFNK)method and Newton-Krylov(NK)method,are a promising choice for effectively solving such complex nonlinear large-scale system.In the first part of this work,the recent progress of numerical calculation for nuclear coupling system worldwide is reviewed,especially,several existing coupling methods are summarized and compared.In the second part,it focuses on the development of simultaneous solution methods as well as the coupling platform for high temperature gas-cooled reactor(HTR)full coupled system by Institute of Nuclear and New Energy Technology(INET),Tsinghua University.Due to the multi-physics,multi-scale,multi-component,multi-circuit and multi-module coupling features in HTR,the key technologies,such as the JFNK method with nonlinear-elimination,scaling factor and steam generator model,were presented and discussed.In detail,the JFNK method with nonlinear-elimination was firstly proposed to deal with the multi-scale temperature coupling between the global pebble-bed and the local fuel sphere.The scaling factor technology was used to transform the ill-posed Jacobian matrix into the well-posed one in the multi-physical coupling issue.For the steam generator model,the dynamical residual method is conducted for the two-phase flow in the second circuit to avoid the multi-solution issue when the phase generation or the phase disappearance occurs.Moreover,a unified framework was proposed to tackle the multi-level coupling structure in HTR system,after several attempts were made.In this framework,the whole coupling system is gradually decomposed into system-level issue,component-level issue and physical field-level issue,and solved as a whole system by the simultaneous solution method.However,to completely solve the whole HTR nuclear power plant system,there are still many works to do,such as the fundamental algorithm research,program framework development and engineering applications.