One of the main research efforts in dry storage of spent fuel is to study the cladding integrity. For this purpose, the understanding of the cladding mechanical performance along the storage period is indispensable, both to analyse the failure probability and to characterize the state of the cladding so that fuel management is conducted with accurate knowledge of the material conditions. However, experimental tests simulating conditions throughout more than 20 years dry storage are impractical, highlighting the need to predict pin behaviour along storage, particularly, under events that can jeopardize cladding integrity. This work is focused on one of the most challenging scenarios for cladding integrity of fuel in dry storage: 100% blockage of cask air cooling. The storage system thermal-fluid-dynamics is modelled with FLUENT (v14.5). A 3D model of a concrete cask has been developed. Based on temperatures calculated, the transient fuel rod mechanics is simulated by an extension of the FRAPCON-3.4 code (FRAPCON-3.4xt). The analytical methodology has been applied to postulated scenarios of a Zry-4 spent fuel rod assuming two different burnups: 40 and 60 GWd/tU. The fuel rod is submitted to 10 days total inlet cask blockage after 25 and 45 years in dry storage. The cladding mechanical response has revealed that creep strain is hardly affected by the postulated event, even in the most challenging scenario (high burnup). Hydrogen related phenomena (i.e., hydride radial reorientation) are discussed, but a quantitative consideration is left out of the scope of this study.
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