Solvent extraction and separation of hafnium from zirconium using Ionquest

industries, its nuclear properties in the pure metallic form make it highly desirable for nuclear applications. Zr is highly corrosion resistant and has a high melting point (2128 K) with a low thermal neutron absorption cross-section of Zr T = 0.18 b, which is significantly smaller than that of hafnium Hf T =115 b) (Speer, 1982), an element that coexists with Zr in nature. This makes Zr ideal for nuclear cladding material and for an inert fuel matrix (Chadwick et al., 2011). Since unrefined Zr metal is more prone to corrosion in a high-temperature aqueous and steam environment (due to metallic and nonmetallic impurities), stringent quality standards have to be met to ensure optimal performance of the zirconium alloy in a nuclear environment. This requires zirconium alloys with a low neutron capture coefficient, high corrosion resistance with regard to nuclear coolants, high manufacturability, and cracking resistance of components during operation, as well as in the manufacturing process itself. While Zr for use in the nuclear industry needs to contain less than 100 ppm Hf, various aspects of metal procurement, purification, and production have to be taken into account to make zirconium alloy of the highest grade. The <100 ppm Hf requirement is likely to be replaced soon by an American equivalent, Zircaloy-4; or Russian equivalent, Zr-1%Nb. These zirconium alloys, which are already in use in nuclear reactors, contain Hf concentrations as low as 42 ppm and 80 ppm respectively (Nikulina and Malgin, 2008). The main impurities found in nucleargrade Zr are titanium (Ti), boron (B), cadmium (Cd), cobalt (Co), manganese (Mn), molybdenum (Mo), sodium (Na), magnesium (Mg), silicon (Si), carbon (C), hydrogen (H), chlorine (Cl), potassium (K), calcium (Ca), fluorine (F), phosphorous (P), oxygen (O), nitrogen (N), iron (Fe), nickel (Ni), chromium (Cr), copper (Cu), aluminum (Al), and hafnium (Hf). The most is known about the effects of O, N, H, C, Si, Al, Fe, Ni, and Hf. The presence of N, C, Al, and Ti results in decreased corrosion resistance (in high-temperature aqueous environments), while the presence of C, H, Si, Cl, P, and F results in decreased fracture toughness and, as a result, poor manufacturability and cracking resistance of parts. Oxygen improves the strength of zirconium alloys, while Fe improves corrosion resistance. Ni intensifies hydrogen absorption, which in turn decreases fracture toughness. The detrimental effects of impurities on the properties of zirconium alloys are synergistic. Solvent extraction and separation of hafnium from zirconium using Ionquest 801