Transient heat transfer in internally heated corium pool

The heat transfer characteristics during different transients are the critical problems in the study of thermal behaviors in volumetrically heated corium pools. In this paper, the COPRA experiments simulating the reactor vessel lower head at 1:1 scale were performed. The nitrate mixture of 20% NaNO₃–80% KNO₃ in mole fraction was employed as the reactor corium simulant. This study mainly focused on the pool temperature change, heat flux variation and crust thickness evolution during two corium relocation stages and heating power transition stages. Then the transient model was developed and the simulation was validated with COPRA tests and reactor case. The calculation results of primary parameters all agreed well with experimental data during entire tests. Furthermore, the model was applied to reactor situation with prototypical corium and compared with LES results.