Investigation of the downcomer boiling phenomena during the reflood phase of a postulated large-break LOCA in the APR1400

摘要

Hydraulic phenomena in the downcomer of a conventional pressurized water reactor have an important effect on the transient evaluations of a postulated large-break loss-of-coolant accident (LBLOCA). In particular, safety analyses using best-estimate codes show that downcomer boiling is one of the important phenomena in the postulated LBLOCA because it can degrade the hydraulic head in the downcomer and consequently affect the reflood flow rate for core cooling. To experimentally identify the thermal-hydraulic behavior in the downcomer, a downcomer-boiling test facility was constructed for simulating downcomer boiling in the reflood phase of a postulated LBLOCA.