Separation of Ni radioisotopes and determination of their activity in a radioactive waste sample using 3D printing

The determination of activities of long-lived activation products present in radioactive waste is essential for radiological safety assessments and waste management. Among these, Ni-59 and Ni-63 are of interest due to their radiotoxicity and persistence in decommissioning materials. In this work, radiochemical methods were applied to isolate Ni isotopes from radioactive waste samples. Custom 3D-printed components were introduced to improve filter fitting and standardize the source-to-detector geometry for Ni-59 determination by low-energy Si(Li) X-ray spectrometry. Ni-63 was determined by liquid scintillation counting (LSC). The nominal absolute detection efficiency values were 2.97.10 −4 for the original geometry and 3.19.10 −4 for the 3D-printed geometry, corresponding to an observed relative difference of 7.4%. This difference was not interpreted as evidence of a statistically significant improvement. Paired Ni-59 activity results obtained with the two geometries were compatible within their expanded uncertainties. Across five independently processed aliquots, the mean Ni-63/Ni-59 activity ratio obtained with the 3D-printed geometry was approximately 54:1, although substantial between-aliquot variability was observed. The results demonstrate the practical usefulness of 3D printing for geometry matching and support further validation using a larger set of samples.