The effect of droplet sprinkling on the oxidation kinetics of zirconium cladding in steam Original Research Article

The influence of oxide layer cracking on the acceleration of Zr cladding oxidation in steam was investigated. Cracking occurs due to temperature gradients, which arise during cooling of the cladding surface by droplet jets. Experimental results on characteristics of heat removal and the temperature gradients induced are presented for different regimes of sprinkling. A model for the calculation of mechanical stresses under the experimental conditions was developed in frame of the theory of envelopes. It was shown that the stresses are sufficiently high to induce cracking of the outer oxide layer. Experimental investigations of oxidation kinetics of Zr-1%Nb cladding were carried out under the conditions of surface cooling by droplet jets. The results of these experiments confirmed that the reaction of oxidation can be strongly accelerated by sprinkling.