Inductively coupled plasma optical emission spectroscopic determination of trace rare earth elements in highly refractory gadolinium zirconate (Gd2Zr2O7)

Abstract

Gadolinium zirconate (Gd₂Zr₂O₇) belongs to the category of burnable absorber (BA) material in nuclear reactors. The high neutron-absorption cross sections of Gd isotopes (¹⁵⁵Gd and ¹⁵⁷Gd) implement negative reactivity in the reactor core to control the excess reactivity of the fuel at the beginning of the fission cycle. The presence of other rare earth elements, which can come from the starting material and/or may be taken up during the synthesis steps, will affect the negative reactivity calculation. Thus the chemical quality assurance of Gd₂Zr₂O₇ concerning the other trace rare earth impurities is indispensable. Here in this work, we decided to quantify thirteen trace rare earth elements in Gd₂Zr₂O₇ by inductively coupled plasma optical emission spectroscopy (ICP-OES). One of the matrix elements viz., zirconium was separated via precipitation using D,L-mandelic acid. The trace rare earths were determined in the presence of gadolinium matrix in solution. It was found that all thirteen rare earth elements can be quantified in the range of 0.25 to 2.5 mg L⁻¹ in the presence of 516 mg L⁻¹ of Gd with a relative standard deviation of 1–3%. This corresponds to the determination of a minimum of 0.25 mg analyte per g of Gd₂Zr₂O₇. The method detection limits of all thirteen rare earth elements range between 0.01 and 0.075 mg g⁻¹. The proposed methodology was validated by analyzing synthetic standards and real samples with spike addition.