Effects of Partial Flow Blockage on Core Heat Transfer in Forced-Feed Reflood Tests

Abstract

This study investigates the effects of partial flow blockage due to ballooning of fuel cladding on the core heat transfer during reflood phase in a PWR loss-of-coolant accident, in particular, the effects of coolant bypass flow at flow blockage and the effects of major parameters in a wide core with a bundlewise flow blockage. Forced-feed reflood tests were carried out with the Slab Core Test Facility, in which 8 simulated fuel bundles are arranged in a row with two out of these designed as blockage bundles with about 60 % blockage ratio. The test results which were obtained under most probable coolant injection conditions were investigated with respect to quench and heat transfer coefficients. As the results, the following were revealed, (1)The effects of flow blockage appear only downstream of flow blockage at the flow blockage bundles with promoted cooling of rods. (2)Effects of coolant bypass flow due to flow blockage are insignificant. (3)Flooding velocity by accumulator injection has a predominant effect on promoted cooling of rods downstream of flow blockage.