Study on the production of Cr-coated Zr-1%Nb tubes as an ATF evolutionary cladding candidate

After some accidents like TMI and Fukushima Daiichi, the belief that nuclear fuels can safely and reliably be used up to 65 MW.d/kgU was revised, and many efforts have been devoted to develope different Accident Tolerant Fuel (ATF) concepts. In this study, an optimized cathodic arc PVD (ARC-PVD) coating condition, from the coating layer homogeneity and defect density point of views, have been obtained. Two coating material (i.e. pure Chromium and Chromium Nitride) with thicknesses up to 10 microns on typical VVER-1000 cladding tubes (Zr-1%Nb alloy) are developed. Presented SEM results approved improvements in coatings visual properties, and further modifications have been postponed until finalizing the performance examinations in normal operational as well as accidental conditions (LB LOCA). Eventyally, the general list of planned tests, from characterizations to mechanical and performance viewpoints, which are currently being carried out, is reported.