Recent study on two-dimensional thermal-hydraulic behavior in PWR core during the reflood phase of LOCA with the slab core test facility (SCTF)

To clarify the mechanism of two-dimensional core cooling behavior during the reflood phase, sensitivity of flooding rate to the core heat transfer and effect of the rod surface temperature were experimentally studied. An increased local flooding rate due to the flow convergence to the high power bundles seemed to be able to enhance the cooling of those bundles, especially in the latter portion of the transient. On the other hand, high temperature core was not cooled well although the higher temperature bundles were cooled down more effectively than the lower temperature bundles in each test, suggesting the importance of the indirect effect of the radial core temperature distribution on core cooling through the two-dimensional fluid behavior. (author)