High-temperature interaction of oxygen-preloaded Zr2Nb alloy with nitrogen

Potential air ingress scenarios during accidents in nuclear reactors or spent fuel pools have raised thequestion of the influence of air, especially of nitrogen, on the oxidation of zirconium alloys, which are usedas fuel cladding tubes and other structure materials. In this context, the reaction of zirconium with nitrogen-containing atmospheres and the formation of zirconium nitride play an important role in understandingthe oxidation mechanism. This article presents the results of analysis of the interaction of theoxygen-preloaded niobium-bearing alloy M5® with nitrogen over a wide range of temperatures (800e1400 C) and oxygen contents in the metal alloy (1e7 wt.%). A strongly increasing nitriding ratewith risingoxygen content in the metal was found. The highest reaction rates were measured for the saturated a-Zr(O), as it exists at the metaleoxide interface, at 1300 C. The temperature maximum of the reaction ratewas approximately 100 K higher than for Zircaloy-4, already investigated in a previous study [1]. The articlepresents results of thermogravimetric experiments as well as posttest examinations by optical microscopy,scanning electron microscopy (SEM), and microprobe elemental analyses. Furthermore, a comparison withresults obtained with Zircaloy-4 will be made. KCI Citation Count: 0