Microstructure Investigation and Mechanical Properties of Coated Zircaloy Cladding

Abstract

Accident Tolerant Fuel concepts have been developed and tested in diverse research programs presently around the world. Industry teams have developed proprietary coating compositions and geometries, but significant knowledge gaps exist in terms of the resulting properties of the coating and the cladding and how those components impact each other in reactor conditions. Furthermore, the national laboratory and university teams currently studying the industry concepts are limited in their ability to freely disseminate and discuss results obtained on commercial coatings. The Advanced Fuels Campaign is therefore working to develop an understanding of 'generic' coatings applied to commercial nuclear cladding alloys free of these constraints. This milestone report provides insights in the microstructure of a 7-micrometer Cr coating on Zircaloy-2 and a 5micrometer coating on Zry-4 as reference materials. SEM and TEM methods were utilized to describe and identify the interface, while nanoindentation was used to determine hardness and E-Moduli of coating and cladding material. This milestone summarizes the acquired knowledge to build a necessary verified foundation for future simulation and qualification efforts.

Impact of Coating Defects on Performance of Coated Zirconium Cladding

“…The geometry and chemical composition of Zircaloy-4 tubes are shown in Table 1. As shown in recent reports [15,16] the surface finish of Zry-4 tubes was not smooth enough for direct coating on the surface of as-received material. Adhesion of the coating was not sufficient, and the directional growth of the coating during the HiPIMS process led to cracks and uncoated areas.…”