Numerical simulation of temperature field in stratified corium and evaluation of nuclear reactor wall melting during severe accident

摘要

Numerical simulation of combined heat transfer for the invessel corium retention problem is presented. An asymptotic description of the natural convection in the corium pool proposed by L. I. Zaichik for high Rayleigh number limit is employed. By use of the effective conductivity model, the transient thermal state of the corium pool with a surface layer of molten steel and the heatign and melting of the reactor vessel are considered simultaneously as a two-dimensional conjugated problem, including the formation of oxide crust layers. The calculations confirm a high local heat flux density toward the wall in the region of the molten steel layer. It has been also found that the steel surface temperature increases considerably to the pool center. The latter result is important for correct evaluations of the radiative flux to overlying in-vessel elements and the vessel wall.