Materials for the cladding tubes of pressurized-water reactors

The operating and design principles of PWR-type reactors impose constraints on the fuel in terms of the materials used and their geometry. Materials are selected to ensure that the fuel meets design and safety criteria.

Two main classes of materials are used in the manufacture of fuel elements: ceramics and metal alloys. As these materials are subject to very severe operating conditions, their justification under current and future service conditions requires :

• in-depth knowledge of the phenomena that develop in these materials under irradiation;

• an analysis of the impact on performance;

• exhaustive and rigorous manufacturing controls.

Components are subjected to thermal, mechanical and chemical stresses, and their properties can be altered by neutron bombardment (see [BN 3 760] ). In addition, the phenomena that govern the behavior of materials can limit their performance. Indeed, the materials used for PWR fuel assembly components have been selected according to the general criteria inherent in nuclear power generation, and more specifically, metallic materials must have certain characteristics, developed below.

The sheathing tube, which forms the first barrier, has a number of major functions. As a result, this component must meet specific requirements.

Based on zirconium alloys, classified into four main families, we'll get to know them better as we read this dossier devoted to materials for pressurized water power reactors (PWRs).