Abstract: In this work, a method for sequential determination of ⁵⁵Fe and ⁶³Ni in spent resins of nuclear power plants was developed. After decomposing the spent resin sample, ⁵⁵Fe and ⁶³Ni ions were first precipitated in the form of hydroxide and subsequently purified by anion exchange chromatography and dimethylglyoxime precipitation. After purification, ⁵⁵Fe and ⁶³Ni were determined by liquid scintillation counting (LSC). The average chemical recovery rate of ⁵⁵Fe and ⁶³Ni was 86% and 90% respectively. The decontamination factors of interfering radionuclides such as ⁶⁰Co, ⁶⁵Zn and ⁵⁴Mn by the sequential determination method were higher than 1 000. The deviation of expected and measured values was less than ±10% through the validation of the analytical method with spiked samples. The measured average activities of ⁵⁵Fe and ⁶³Ni in a set of spent resin samples from its primary loop of a nuclear power plant were (76.2±1.4) kBq/g and (120.0±5.1) kBq/g, respectively.

Key words: ⁵⁵Fe, ⁶³Ni, spent ion-exchange resin, LSC, sequential determination