Thermal margin evaluation for the stratified molten pool in SMR-IP200

Abstract

In this paper, a simple model for stratified corium pool is built based on the concept of FIBS, to estimate the IVR thermal load of IP200 reactor (which is a small modular reactor with thermal power 220 MW). For the model validation, the IVR benchmark of AP600 reactor is calculated, and the results are compared with that of UCSB and INEEL. Then, the molten pool of IP200 with two-layer, three-layer and water-layer configurations are calculated respectively. The thermal load distributions with the effects of internal power and metal mass are analyzed. Besides, the changes of peak heat flux, which are caused by the heavy metal’s appearance and the water layer’s boiling, are discussed by the comparison of local CHF. The specific results show that, in two-layer configuration, the peak heat flux is within 279.9–667.8 kW/m2, and the thermal margin is within 0.31–0.74. In three-layer configuration, the bottom heat flux of molten pool will be enlarged. The internal heat of heavy metal can be the dominant factor for the thermal load fluctuation, when the mass composition is changed. In water-layer configuration, considering the heat transfer of film boiling can keep in a same magnitude as that of radiation, the heat dissipation of pool’s upper face will be enhanced to mitigate the peak heat flux. The present work gives out some key values of steady-state IVR under different configurations, which can provide some references for the safety evaluation of SMR.