Effect of cationic substitution in the oxidative decontamination processes of nickel chromium ferrites

Addition of Zn²⁺ and Mg²⁺ ions to the coolant water is followed in boiling and pressurized water reactors to control the radiation field. These cation additions modify the composition of double-layered spinel nickel chromium ferrite oxide films formed on stainless steel. The primary objective of this paper is to offer a systematic perspective for comprehending the dissolution behaviour of non-stoichiometric oxides upon Zn²⁺ and Mg²⁺ addition. In this regard single-phased nickel chromium ferrites were synthesized and characterized by various techniques. The crystal morphology and band gap changed with an increase in lattice dimensions upon incremental substitution of Ni. The oxidative dissolution rates increased with increasing Mg²⁺ or Zn²⁺ in the Ni–Cr–Fe–O lattice with a maximum at x = 0.6. Magnesium-substituted nickel ferrites showed a higher dissolution kinetics compared to their zinc-substituted counterparts. The dissolution behavior and kinetics are explained on the basis of cation redistribution in the octahedral or tetrahedral sites of the spinel lattice. The Laser Raman Spectroscopic (LRS) analysis corroborated the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) observations. These results will provide an insight into the mechanism of radioactivity removal kinetics for developing effective dose rate reduction practices for nuclear plants.