NRC SFST ISG-22: POTENTIAL ROD SPLITTING DUE TO EXPOSURE TO AN OXIDIZING ATMOSPHERE DURING SHORT-TERM CASK LOADING OPERATIONS IN LWR OR OTHER URANIUM OXIDE BASED FUEL

Under the current guidance in ISG-1, Revision 1, “Damaged Fuel,” the definition of intact fuel
includes fuel rods containing no cladding defects greater than pinhole leaks or hairline cracks.
During the cask water removal process parts of, or all of, the fuel rods will be exposed to a
gaseous atmosphere. If the gaseous atmosphere is oxidizing, oxidation of fuel pellets or fuel
fragments can occur if a cladding breach exists (such as a pinhole). Oxidation may occur
rapidly and cause significant swelling of fuel pellets and fragments, which could result in gross
fuel cladding breaches if the time-at-elevated-temperature after water removal is excessive (see
Appendix to this ISG).