Zirconium determination by cooling curve analysis during the pyroprocessing of used nuclear fuel

Abstract An alternative method to sampling and chemical analyses has been developed to monitor the concentration of zirconium in real-time during the casting of uranium products from the pyroprocessing of used nuclear fuel. The method utilizes the solidification characteristics of the uranium products to determine zirconium levels based on standard cooling curve analyses and established binary phase diagram data. Numerous uranium products have been analyzed for their zirconium content and compared against measured zirconium data. From this data, the following equation was derived for the zirconium content of uranium products: Zr = 0.14 M + 131.56 - 12.63 ( 348.65 - 0.16 LT ) 1 / 2 where M is the mass (kg) of the ingot and LT is the liquidus temperature (K) found by cooling curve analyses. Based on this equation, a reasonable fit of calculated to measured zirconium content was established considering the errors in the system.