Transient heat transfer analysis of double-layer molten pool under severe accident

ABSTRACT

Reactor safety is crucial to the development of nuclear energy. In a severe accident, after the core of a nuclear reactor melts and collapses, the use of in-vessel retention external reactor vessel cooling (IVR-ERVC) technology can effectively alleviate the heat flux at the lower head and ensure the intactness of the lower head. The different densities of the melt result in stratification in the molten pool (neglect thermochemical effects and two layers are immiscible). The molten pool structure is investigated based on single-, double-, and triple-layer molten pool structures. Based on a third-generation nuclear reactor, the ANSYS commercial software is used to establish a three-dimensional geometric model of the double-layer melt. A large eddy simulation is performed to comprehensively analyze the turbulent heat transfer characteristics of the molten pool with a bulk heat source. Wall-Modeled Large eddy simulation (WMLES), Volume of Fluid (VOF), and phase change models were used in this work, for example, nature convection, temperature field, and heat flux distribution were all investigated. The temperature field, velocity field, and heat transfer of the vessel outer wall are compared for two different boundary conditions of top radiation and top cooling on the light metal layer. The transient heat transfer characteristics of the molten pool under IVR-ERVC conditions are investigated to provide a basis for further investigations.

Graphical abstract

KEYWORDS:

• Severe nuclear accident
• double-layer melt
• IVR-ERVC
• turbulent heat transfer
• large eddy simulation

Acknowledgments

This research was supported by the National Natural Science Foundation of China (12175188), Fujian innovation strategy research program (No. 2020R0011), and XMU Training Program of Innovation and Entrepreneurship for Undergraduates (2021X1173 and 2021Y1337).

Disclosure statement

No potential conflict of interest was reported by the author(s).