Reactor grade zirconium

Reactor-grade zirconium is essentially free of hafnium. Zircaloy(R) is an important alloy developed specifically for nuclear applications. Zirconium is exceptionally resistant to corrosion by many common acids and alkalis, by sea water, and by other agents. Alloyed with zinc, zirconium becomes magnetic at temperatures below 35oK. 

Zirconium Zirconium was originally developed as a construction material for atomic reactors. Reactor-grade zirconium contains very... 

To reduce the hafnium content below the 0.01 w/o specified for reactor-grade zirconium, the solution of zirconium and hafnium in molten zinc at point 3 is contacted in step B with a liquid mixture of 0.1116 mol Znp2 and 0.1116 mol NaP. Reactions... 

Figure 7.9 Megy process for producing reactor-grade zirconium from natural sodium fluozircon-ate. Material quantities in moles. Basis, 1 mol zirconium product.-----salt ------ metal.

Figure 7.10 Production of reactor-grade zirconium from zircon by combination of K2SiFg fusion and Megy process.

The number of structural materials available for use in reactor applications is limited. The most stringent requirement is a low thermal neutron capture cross section. Among common materials, only aluminum has a sufficiently low cross section to permit its extensive use in reactors using natural or slightly enriched uranium as fuel. The need for other materials, particularly for use at elevated temperatures, resulted in the development of reactor grade zirconium and zirconium alloys. 

Although the solvent purification process is adequate for the production of say reactor-grade zirconium, it is possible to modify it so that pure hafnium may also be obtained. Distribution data are available for various solutions containing thiocyanate, sulphate and chloride from which it is possible, for example, to deduce that both hafnium and zirconium will extract into hexone provided the aqueous phase has a high thiocyanate concentration and a low chloride concentration. The zirconium may then be selectively backwashed in a second extractor using say an aqueous phase of high thiocyanate concentration and moderate sulphate concentration, where the separation factor of the system is high. The hafnium can then... 

Compact process route for reactor grade zirconium production... 

Figure 6.1.1 / new process for producing reactor grade zirconium... 

As it occurs in nature, zirconium is always found in association with hafnium, in the ratio of 1 part hafnium to 50 parts zirconium, and commercial-grade zirconium contains approximately 2% hafiiium. Because hafnium has a high absorption capacity for thermal neutrons, nuclear reactor-grade zirconium is not permitted to contain more than 0.025% Hf, and usually it contains closer to 0.01%. 

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