There are several cladding properties that may become significant in the management of spent fuel. Typical changes are rod growth and clad hardening. During reactor operation, the cladding undergoes corrosion in water resulting in the formation of hydrogen. Some of this hydrogen is taken up by the cladding and contributes to the reduction of cladding ductility.

The mechanisms of corrosion in PWRs and BWRs are somewhat different but the results may be similar. The corrosion of cladding can lead to an increased driving stress intensity factor (due to changes in the local chemical potential and local geometry) for cladding breach due to delayed hydride cracking (DHC) (ref 1410). Hydriding can affect ductility and can lead to a cladding breach during an accident. Another feature of the cladding that affects spent fuel management is crud deposition on the rod surface. Crud can be found on the cladding in very different amounts dependent on the individual reactor but it also seems to be dependent on the fuel burnup. The experience shows that for some unknown reason crud is not a problem in Russian WWER reactors or in some PWRs in Europe.

Crud is the only source of radioactive particulates that can be released without a fuel cladding breach and it presents a dose risk if the fuel storage containment is breached.