Mechanism and Conditions for Continuous Hydride Layer Formation in Zirconium Cladding

Abstract

Local hydrogenation of zirconium fuel-element cladding, resulting in the formation of continuous hydrides, as a rule occurs when coolant or other hydrogen-containing compound finds its way beneath the fuel-element cladding irradiated in the core of a water moderated and cooled reactor. In this article, the set of processes occurring during hydrogenation of zirconium cladding is analyzed, and estimates are given for the parameters of these processes. The conditions and mechanism of formation of a continuous hydride over the thickness of zirconium cladding are established. It is shown that the duration of the nucleation of the hydride is determined primarily by the time to local destruction of the oxide film on the inner surface of the zirconium cladding of the fuel elements. The shortest possible time for continuous hydride to grow through the thickness of fuel-element cladding is determined.