[en] Out-of-pile experiments with zircaloy-clad fuel rods and bundles are being performed to investigate the behavior of PWR fuel rods under severe fuel damage conditions. Of particular interest are temperature escalation due to the exothermic zircaloy/steam reaction and processes inherently limiting the reaction. In every test performed, measured temperatures never exceeded 2250⁰C. Temperature limiting processes which have been observed include runoff of molten zircaloy from the reaction region and formation of a thick oxide layer. Metallographic and microprobe analyses of rod and bundle cross sections were performed to identify the damage mechanisms. (orig.)