Failure Modes of Fuel Cladding

Overheating of fuel pellets Fuel centerline temperature (°C)  

Numbers in parentheses indicate values for blanket fuel rods 

Collapse failures have not been a concern in LMFBRs due to the low coolant pressure. Rather, mpture of cladding has been a greater concern in LMFBRs than collapse. Rod internal pressure is always higher than coolant pressure. Only hoop tensile stress is a consideration. 

Rod overpressure has been considered as a hypothetical cladding failure in LWR fuel rod designs. If rod internal pressure becomes larger than coolant pressure, outward creep of fuel cladding may start. If outward creep rate exceeds the fuel 

Fretting of the fuel rods has been considered a failure mode. It results from erosion by debris collecting at the interference between the fuel rods and grid spacers or flow induced vibratimi (HV) of the fuel rods and grid spacers. Corrosion, hydriding and embrittlement of cladding at LOCA have also been regarded as fuel failure modes in LWRs. 

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