By use of the TOODEE2-J computer program, an analysis was carried out of the fuel rod behavior, and core damage was estimated for the TMI-2 reactor during the first three hours of the accident on March 28, 1979. The boundary conditions (e.g. core mixture level, steam flow rate and core inlet flow) are based on a thermal-hydraulic analysis by the RELAP4/MOD6/U4/J2 computer program. The calculated results suggest that bursting of almost all rods except peripheral low-powered rods occurred, and that a large part of the zircaloy cladding exceeded the eutectic temperature to form a liquid phase of ZrUO. A total of 43.5% of the zircaloy in the fueled part of the core had been converted to zirconium-dioxide by three hours into the accidient, and major damage to the fuel rods had also occured by then.
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