Molten Corium–Concrete Interaction: Investigation of convective heat transfer in a pool with gas sparging

Abstract

During a severe accident in a Pressurized Water Reactor, corium may fall in the reactor pit and interact with concrete. The CLARA setup, financed by EDF, IRSN, GDF-Suez and CEA, has been designed to understand the heat transfer phenomena involved in the Molten Concrete Corium Interaction (MCCI). The facility is composed of a pool of simulant liquids, percolated by air and internally heated by direct electrical current. It is in contact with several heat exchangers in order to maintain walls at a constant temperature and to measure local heat losses. The experiments performed aimed at studying the influence of liquid viscosity (varying from 1 to 10000 mPa.s by dissolution of hydroxyethyl cellulose in the water), air injection velocities (ranging from 0 to 10 cm/s) on both horizontal and vertical walls and pool length, on heat transfer distribution. This paper presents the findings on heat transfer which would contribute to the understanding of MCCI. After a literature review on the existing heat transfer experiments and correlations for two-phase (liquid-gas) flow, the CLARA experiments are described. Then, the results obtained are presented: influence of superficial gas velocity and liquid properties (especially viscosity) on heat transfer, evaluation of ratio between heat transfer on vertical and horizontal interface, influence of the pool dimensions. Finally, the analysis and interpretation of CLARA experiments are given: comparison to the literature data, development of correlations concerning the heat transfer along the vertical and horizontal plate, comparison to results obtained with real materials.

Heat & mass transfer and interface temperature during simulated melt-concrete interaction with composition variation in ARTEMIS 2D experiment

“…Michel and Cranga proposed a heat-transfer model based on thermal resistances due to a slag layer and convection (Cranga et al, 2010(Cranga et al, , 2013. Separate-effect tests with simulant materials have also been initiated to investigate the link between heat-flux distribution, viscosity and the distribution of superficial gas velocity more precisely (CLARA tests (Amizic et al, 2012;Bottin et al, 2015Bottin et al, , 2016). One important result was that pool thermal-hydraulics alone cannot explain the 2D ablation results observed during MCCI experiments and that material effects certainly play an important role.…”

Numerical Simulation of Pressure Wave Propagation and Its Effect on Damage to the Reactor Cavity under TNT Detonation for Steam Explosion

“…Using a density of 7960 kg/m 3 for the molten corium [34], the mass of all of these substances is calculated to be 557.2 kg. The heat capacity of the molten corium, consisting of 80% fuel (UO 2 ) and 20% oxidized cladding material (ZrO 2 ) has become approximately 1298 kJ/kg at 2800 K [35]. Consequently, the total thermal energy in the virtual cylindrical column is calculated to be approximately 723,246 kJ.…”