Effect of fuel rod failure on emergency core cooling system design for boiling water reactors

The experimental results of fuel rod failure on the heat transfer effectiveness of spray cooling a Zircaloy-clad simulated BWR fuel bundle were evaluated from the design engineer viewpoint to determine the adequacy of the emergency core cooling system (ECCS) design. The overall results of the full-size 49-rod Zircaloy-clad internally pressurized bundle indicate that the ballooning and perforation associated with cladding failure did not significantly change the heat transfer effectiveness (i.e., peak cladding temperatures) of the ECCS spray cooling mode. Furthermore, the distortion was local in nature so the flow area reduction would not affect the ability of the ECCS flooding mode to accomplish the design objectives.