Analytical Quality Control in the Production of Nuclear Grade Zirconium and its Alloys

Abstract

The chief application of zirconium metal and zircaloys is in nuclear reactor engineering as cladding material for the fuel elements and as structural material in the construction of reactor cores. The selection is based on considerations of low neutron absorption cross section, fabricability, corrosion resistance and mechanical stre-ngth at elevated temperatures. These properties are however sensitive to impurity levels and alloying compo-sitions.For example, for neutroneconomy the hafnium and boron contents should be within 200 ppm and 0.5 ppm respectively; for corrosion resistance the aluminium, carbon and nitrogen tolerances are respectively only 75 ppm, 500 ppm and 50 ppm; and for ease of fabrication the maximum permissible oxygen content is 1500 ppm. In the large scale production of zirconium sponge and zircaloy ingots, it becomes therefore essential to have a strict control of impurity levels in the successive stages of the batchwise production, in order to ensure consistency of quality and performance in the finished product.