X-ray Fluorescence Determination of Small Quantities of Hafnium in Nuclear Pure Zirconium-Based Materials

An important chemical impurity in the composition of zirconium-based materials for nuclear power engineering is hafnium, the content of which should not exceed 0.05 and 0.01% for Russian and foreign alloy grades, respectively. Since the chemical properties of hafnium are similar to those of zirconium, determination of this element using classical methods of analytical chemistry is a challenging problem. Among the physical methods, the X-ray fluorescence method is the most expressive, which is important under conditions of continuous production. The X-ray fluorescence method for measuring the content of hafnium in zirconium-containing material has been tested by the example of potassium fluorozirconate, a precursor for obtaining alloys. Using various combinations of crystal analyzers, detectors, and collimators of a wave-dispersive spectrometer, the ratios of the intensities of the Hf and Zr analytical lines in the second order of reflection have been refined, and the degree of decrease in the fluorescence intensity of those lines has been determined. The X-ray fluorescence spectra of hafnium lines in potassium fluorozirconate have been studied for the content characteristic of nuclear-pure zirconium. The possibilities of recording the intensity of the Hf analytical lines and methods for eliminating the interference from the Zr lines in the second order of reflection are considered. The metrological characteristics of the determination of Hf using selected analytical lines have been calculated. It is shown that the error is the smallest and the detection limit is the lowest (0.001%) if the HfLβ1 line is used with certain settings of the wave-dispersive spectrometer (the X-ray tube operating mode, a combination of a crystal analyzer, a detector, and a collimator, and the amplitude discriminator settings). The proposed method of hafnium determination is applicable to the materials with a constant content of zirconium.