Multi-parametric study of welding parameters on the durability of CANDU fuel assemblies

Amane Sahli; Nourelislam Bouderhem; Mohamed Sadouki; Omar Menchi; Belkacem Rabah  Ahmed Walid; Sofiane Mekideche; Oussama Djema

Amane Sahli Nuclear Research Center of Draria CRND, Algiers, Algeria
Nourelislam Bouderhem National Polytechnic School of Algiers ENP, Algiers, Algeria
Mohamed Sadouki Nuclear Research Center of Draria CRND, Algiers
Omar Menchi Nuclear Research Center of Draria CRND, Algiers, Algeria
Belkacem Rabah Ahmed Walid Nuclear Research Center of Draria CRND, Algiers
Sofiane Mekideche Nuclear Research Center of Draria CRND, Algiers, Algeria
Oussama Djema Research Centre in Semiconductors Technology for Energetics CRTSE; Algiers, Algeria

Keywords: TIG welding, Zircaloy-4, Fuel rod assemblies, CANDU, Fusion zone, Heat-affected zone, Widmanstätten structures, Burst test

Abstract

This study focuses on TIG (Tungsten Inert Gas) welding of Zircaloy-4, used in fuel rod assemblies for CANDU (Canada Deuterium Uranium) reactors, to analyze the effect of welding parameters on the microstructural and mechanical quality of end-plug-to-cladding joints. Despite the extensive use of TIG welding for Zircaloy-4, understanding the induced metallurgical phenomena that affect mechanical properties remains a major challenge. This study aims at systematic characterization of welding parameter effects on microstructure and properties of plug-cladding joints, identifying metallurgical zones and correlating operating conditions with final performance. Welds were produced under various conditions of current intensity and rotation speed and examined using optical microscopy, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Vickers microhardness, and hydraulic burst tests. The analysis revealed three distinct zones: fusion zone (FZ), heat-affected zone (HAZ), and base metal (BM) with typical Widmanstätten structures. A clear correlation was found between heat input, hardness, and mechanical strength. Hydraulic burst tests confirmed the high performance of optimized welds, showing failure stresses of approximately 425 ± 10 MPa.

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