Zirconium hydrogen evolution

Another example of chemical decladding is afforded by the Zirflex process, which was proposed for zircaloy-clad UOj fuel before mechanical decladding was fully developed. In the Zirflex process [S17], zirconium or zircaloy cladding is dissolved as ammonium fluozirconate in a boiling solution of ammonium fluoride containing ammonium nitrate, the latter added to reduce hydrogen evolution. Overall reaction is approximately... 

Reaction of this well-characterized species with dry hydrogen at 150°C leads to the formation of zirconium hydride and the evolution of alkanes.257 Hafnium and titanium monohydride can be obtained in the same way.258... 

Ehrlich 160) reports that zirconium trifluoride is stable in air to 300°C, and stable to disproportionation at 850°C. In addition, it is reported as being difficulty soluble in hot water, and soluble in warm mineral acids without evolution of hydrogen. This is inconsistent with the conclusion of Straumanis 539) that zirconium trifluoride is an inter-... 

In order to proceed with the fractionation, the zirconium hafnium phosphates must be converted into acid-soluble compounds. Digestion of the moist phosphates with a mixture of sodium hydroxide and sodium peroxide yields a dense white peroxy compound, which can be washed free from the soluble phosphates, and which is soluble in acid with the evolution of oxygen. This reaction is utilized in the following procedure, except that 30 per cent hydrogen peroxide has been substituted for the sodium peroxide. 

PRACTICE EXAMPLE B Most nuclear power plants use zirconium in the fuel rods because zirconium maintains its structural integrity under exposure to the radiation in the nuclear reactor. The nuclear accidents at Three Mile Island, Chernobyl, and Fukushima involved the evolution of hydrogen gas from the reduction of water. The half-cell reduction potential for Zr is... 

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