Methodology for a realistically conservative characterization of spent fuel in dry storage

Abstract

The characterization of spent fuel in dry storage is fundamental to assess and assure the cladding integrity as one of the main safety criteria. To do that, reliable methodologies based on applicable analytical tools are pursued. The present paper shows an easy to apply methodology to characterize dry stored fuel from a realistically conservative approach. It has been validated through EOL rod internal pressure data from PWR fuel rods. The application to old and current designs of discharged fuel rods shows cladding stresses below the limit usually applied for embrittlement due to hydride radial reorientation (90 MPa). An analysis of the stress reduction with respect to enveloping conditions (licensing limits concerning irradiation and stored heat load) points out the importance of approaching realistic power histories (stress reduction higher than 30%), whereas the realism sought in the stored heat load is shown to be less important (stress reduction around 12%).