| 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. |
