Experimental Study of ECC Water Injection Rate Effects on Reflood Phase of PWR-LOCA

Abstract

The effects of the ECC water injection rate on reflooding behavior during a PWR-LOCA have been investigated using the experimental data from a large scale reflood test facility. As a general result, the higher ECC water injection rate was found to result in the higher core flooding rate, and hence, the better core cooling. However, when the LPCI injection rate was higher than a certain value, which was enough to keep the downcomer almost filled, the core flooding rate was found to become an almost identical value being regardless of the LPCI injection rate. Also found was the effect of the Acc injection rate and duration influenced the core cooling behavior through the whole transient including the LPCI period. These phenomena have been analyzed and clarified quantitatively in this paper. It was also found that the Acc injection rate and duration effects on reflooding behavior observed in the large scale facility were almost the same as those already observed in the small scale facility.

KEYWORDS:

• reactor safety
• loss of coolant
• reflood experiment
• PWR type reactor emergency core cooling system
• accumulator system
• low pressure coolant injection system
• heat transfer
• two-phase flow
• flow rates