Experimental Study of Initial Downcomer Water Accumulation Velocity Effects on Reflood Phase of PWR-LOCA

Abstract

The effects of the initial downcomer water accumulation velocity on the thermo-hydrodynamic behavior during the reflood phase of a PWR-LOCA have been investigated experimentally by using the Cylindrical Core Test Facility (CCTF), which is the largest integral test facility for the investigation of the reflooding behavior, in order to clarify whether the larger downcomer flow area of the CCTF than the PWR scaled value causes the differences in the reflooding behavior. This is because the downcomer flow area of the CCTF is larger than the PWR scaled value by 70% and the main influence to the reflooding behavior caused by this is considered to be the initial downcomer water accumulation velocity effects. Analyzing the experimental data, it has been found that the influence of the initial downcomer water accumulation velocity on the reflooding behavior is very small under the CCTF base case test condition. Therefore, it has been confirmed that although the downcomer flow area of the CCTF is 1.7 times as large as the PWR scaled value, with regard to this point, there are practically no problems in applying the CCTF test results to the PWR analyses.

KEYWORDS:

• cylindrical core test facility
• downcomer
• emergency core cooling system
• flow area
• flow rate
• loss of coolant
• PWR type reactors
• reactor safety
• reflood experiment
• velocity