Experimental Study on Difference in Reflood Core Heat Transfer among CCTF, FLECHT-SET and Predicted with FLECHT Correlation

Abstract

It has been reported that the core heat transfer coefficients measured in the CCTF tests, which were conducted under the conditions expected to appear during the refiooding period in a PWR, can not be predicted well with the FLECHT correlation, which has been used in the safety evaluation. In order to investigate the reason for this, a CCTF test was conducted under the typical FLECHT-SET experimental conditions. Investigating results from both tests, the following has been clarified:

The FLECHT correlation can not describe the heat transfer for the refiooding situations with the initial Accumulator injection period, which is expected to appear in a PWR, and gives much lower values than the measured. The core heat transfer in the FLECHT-SET is similar to that in the CCTF, and they are well predicted with the Murao-Sugimoto correlation. When there is some core radial power distribution, which strongly affects the heat transfer in a large vScale core, the heat transfer coefficients in the CCTF can be well predicted with taking account of this effect in addition to the Murao-Sugimoto correlation.

KEYWORDS:

• reactor safety
• PWR type reactors
• loss of coolant
• ECCS
• refiooding
• CCTF-test
• FLECHT-SET-test
• core heat transfer
• FLECHT heat transfer correlation
• Murao-Sugimoto heat transfer correlation
• multi-dimensional effects
• core radial power distribution
• experimental data