Determination of critical trace impurities in “uranium silicide dispersed in aluminium” nuclear fuel by inductively coupled plasma mass spectrometry (ICP-MS)

Abstract

The quality assurance (QA) of nuclear materials is one of the most important aspects of the chemical quality control (CQC) program for the safe operation of nuclear reactors. The characterization of trace impurities in the starting materials and fabricated products is one of the stepping-stones in the overall QA process. Depending on the reactor design and operational conditions, these trace impurities have different specification limits in nuclear materials. Reports of analytical methodologies for their precise and accurate quantification are limited in literature, and “uranium silicide dispersed in aluminium” (U₃Si₂–Al) is no exception. U₃Si₂–Al is one of the most important nuclear fuels for the conversion of research and test reactors employing highly enriched uranium to the one employing low enriched uranium. A novel three-step matrix separation procedure was developed in this study for the quantification of seven critical trace impurities viz., B, Cd, Hf, Eu, Sm, Gd, and Dy in U₃Si₂–Al by inductively coupled plasma mass spectrometry (ICP-MS). The matrix elements, Si and Al, were separated by the offline pretreatment of the sample, whereas U was separated online before nebulizing the sample into ICP-MS. The online nebulization-assisted solvent extraction of U by a stationary extractant phase has reduced the liquid waste generation drastically. The validation of the proposed analytical methodology was done by spike addition and recovery studies in three real U₃Si₂–Al samples. The analyte recoveries were found to be ≥95%. The relative standard deviations (RSDs) on the determined quantities were observed within 8%.