In-situ neutron radiography investigations of the reaction of Zircaloy-4 in steam, nitrogen/steam and air/steam atmospheres

In the framework of nuclear safety research the high temperature reaction behavior of the classical pressurized water reactor cladding material Zircaloy-4 in nitrogen containing wet atmospheres was investigated by means of in-situ neutron radiography. The paper describes experimental details and gives an overview of the results. The dependence of the reaction rate on the sum of oxygen + steam flux is discussed and compared with a model developed at KIT. The results confirm the, at first glance surprising, prediction of the model that the time of the transition from parabolic to linear kinetics increases and the post-transition reaction decreases with increasing flow rate of oxygen + steam.