After reviewing some old threads (e.g. here), anecdotally I see that fuel rods do suffer failures on occasion, but it appears not very often, as is intended. My question is, why not more frequently? Given a power reactor neutron flux of 1014 n/cm2-s, it seems like every atom in the cladding wall must suffer dislocation dozens of times over the couple years of fuel life in core, and the internal pressure from fission product gasses IIRC builds to many tons over the entire rod. Similarly, the structural supports directly in contact with the fuel assembly have no coolant-moderator separation to thermalize fast neutrons, so that those structural supports would also appear to be subject to rapid disintegration.