Volume 7, Issue 8 (September 2010)
Segregation in Vacuum Arc Remelted Zirconium Alloy Ingots
Vacuum arc remelting of zirconium alloy ingots is a key step in the manufacturing process of fuel assembly components in nuclear reactors. The control of the analytical homogeneity is indeed fundamental to ensure the quality and the in-reactor performance of the final products. For this reason, together with other industrial companies, AREVA NP/CEZUS has undertaken for more than 20 years a partnership with the Nancy School of Mines, which has developed a specific code named SOLidification during Arc Remelting (SOLAR). The mathematical model is based on the solution of the coupled transient heat, momentum, and solute transport equations, under laminar or turbulent flow conditions, during the remelting and cooling of a cylindrical ingot. An important part of the overall work is the careful validation of numerical simulations. For this purpose, specific sets of thermophysical data have been determined for various zirconium alloys. The model results show good agreement with the observation of 6 tons ingots remelted under industrial conditions. The specific case of a single melt M5™ ingot was recently studied. The corresponding results are presented and discussed. The chemistry analysis has been enriched with structure examinations, aiming at improving the knowledge of solidification mechanisms in zirconium alloys. The use of SOLAR code to evaluate the ingot chemistry contributes to constantly improving the melting process applied to zirconium alloys in AREVA NP/CEZUS.