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 strength at elevated temperatures. These
properties are, however , sensitive to impurity levels
and alloying compositions . For example , for neutron economy the hafnium and boron contents should be within
200 ppm and 0'5 ppm respectively : for corrosion resi-stance 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 there-fore 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
