Computation of Solid Melting With Wall Boiling Under External Reactor Vessel Cooling

The solid wall convection melting physics is computed with coupling external boiling physics based on the volume-of-fluid model in the STAR-CCM+ code. A three-dimensional rectangular computational sample domain is used with 5.0 cm height, 4.0 cm width and 1.0 cm depth. This domain is separated by carbon steel representing a reactor vessel section in contact with water channel representing the gap between the reactor vessel outer surface and the insulation. The flow rate of the bottom inlet flow in the water flow channel is 2 × 10⁻² kg/sec with temperature at 92 °C. The concentrated heat flux of 2.1 MW/m² obtained from a typical APR1400 reactor condition is imposed at the center of the left wall of the solid region. At the same time, subcooled water entering the right channel boils and the vapor film covers the surface which expedites melting process in the solid heated region. Important finding is that solid wall melt-through is not expected as far as for the present analysis conditions and there is a minimum water flow rate below which the rate of solid melting is saturated.