The performance and structure of final nuclear zirconium alloy components is formed at all processing steps, from ingot melting and subsequent forging, quenching, pilgering, and heat treatment. The subject of this investigation was the structure of zirconium alloy ingots made by double melting in a vacuum arc furnace, and investigated by the use of radioactive indicators (RAIs). The isotopes that were used were W¹⁸⁵ and C¹⁴, which were added in very small quantities to the charge before melting the ingot. The RAI isotopes decorate the ingot structure, and provide an opportunity to investigate the behavior of impurity levels during solidification of the molten pool, and the structure in the various types of solidification zones within the ingot. The forged material and other products were investigated using the C¹⁴ isotope. Carbon distribution data were obtained for both Zr2.5Nb and for E635 structures on both macroscopic and microscopic levels. The structures and phases in which the carbon isotope was concentrated were discovered.