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

Abstract

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.

Keywords

• multi-physics
• multi-scale
• multi-component
• multi-circuit
• multi-module
• high temperature gas-cooled reactor
• jfnk