THERMOHYDRAULICS OF BOILING 2-PHASE FLOW IN HIGH CONVERSION LIGHT WATER-REACTORS (THERMOHYDRAULICS AT LOW VELOCITIES)

With the aim of obtaining a fundamental data base with regard to HCLWR (high conversion light water reactor) core thermo-hydraulics, the effect of channel gaps on thermo-hydraulic behavior is investigated, particularly at low velocities as these may be assumed to occur under various abnormal operating conditions in HCLWRs. Boiling heat transfer and frictional loss are investigated experimentally, and the applicability of the drift flux model to narrow channels is examined. Finally, the reflooding behavior is investigated experimentally in relation to a postulated loss-of-coolant accident in HCLWRs. It has been made clear from the results that the incidence of a pressure drop during the reflooding phase is much higher than that in current LWRs.