COTELS Project (1): Overview of Project to study FCI and MCCI during a Severe Accident

Fuel coolant interaction (FCI) and molten core concrete interaction (MCCI) have been studied experimentally within the framework of COTELS project from 1995 as a joint study between NUPEC (Japan) and NNC (Republic of Kazakhstan) using one of the testing complex at NNC. The testing complex includes three experimental facilities “SLAVA”, “LAVA” and “LAVA-M” for debris coolability tests. Three types of experiments were carried out. To get the molten corium, the electric induction melting furnace (EMF) was used. The EMF produced ∼60 kg of corium containing UO2, stainless steel, Zr and ZrO2. The temperature of the produced melt was about 3200 K. The melt was discharged into the water pool in Test A or onto the concrete trap in Test B/C. The corium in the concrete trap was heated in Test B/C by another induction melt heater. Prior to main Test A and Test B/C, several supporting experiments were conducted. Integrity of graphite crucible with TaC sheet during producing UO2 corium was confirmed experimentally. The induction melt heater was calibrated and the efficiency for the induction heater of “LAVA-M” facility was determined as 47%. The thermal conductivity and thermal diffusivity of concrete up to about 1073 K, and melting–solidification points of eutectics generated from corium components were determined experimentally. Discharge corium behavior, using UO2 corium, was also observed by speed cameras in Test 01.