[en] Studies of the rupture and flow blockage characteristics of full-length Pressurized Water Reactor fuel rods under LOCA conditions have been performed to evaluate maximum cladding strain conditions for hypothetical ''flat top transients'' in the high-alpha temperature range. This work, performed as part of the ''LOCA Simulation in NRU'' program, was sponsored by the United States Nuclear Regulatory Commission (NRC) and the United Kingdom Atomic Energy Authority (UKAEA). Cladding ballooning and rupture in the high-alpha temperature range of 1023K to 1123K reach a maximum condition. Three nuclear-heated full-length 32-rod PWR fuel bundle tests have been performed in this temperature range. The results of these tests indicate that although individual rod strains at the rupture site of 50% to 60% are common, peak average bundle strains of the ruptured rod never were greater than 37%. Ballooning in all cases extended over a length of at least 150 cm. There was no apparent degradation in bundle heat transfer. (author)