Separation of protactinium from uranium-niobium alloys for 231Pa-235U radiochronometry in nuclear forensic investigations.

The isolation and purification of protactinium from uranium materials is essential for 231Pa-235U radiochronometry, but separating Pa from uranium-niobium alloys, a common material in the nuclear fuel cycle, is challenging due to the chemical similarity of Pa and Nb. Here we present three resin chromatography separation techniques for isolating Pa from U and Nb which were independently developed by three different laboratories through ad hoc adaptations of standard operating procedures. Our results underscore the need for and value of purification methods suitable for a diversity of uranium-based materials to ensure the operational readiness of nuclear forensics laboratories. Supplementary Information: The online version contains supplementary material available at 10.1007/s10967-023-08928-y.

Quantifying surface roughness on UO2 fuel pellets using optical techniques.

Rapid, non-destructive nuclear forensic techniques can aid in signature development and provide valuable information for provenance assessments. Using optical profilometry and digital microscopy, we studied the surface roughness of fuel pellets to probe its usefulness as a forensic signature and its relationship to a given producer's grinding techniques. Arithmetic average areal (Sa) surface roughness measurements provide a rapid, non-destructive technique, producing efficient measurements with smaller standard uncertainties relative to 2D, arithmetic average profile (Ra) surface roughness measurements. Digital microscopy proved to be the superior technique over optical profilometry, in part due to its higher image quality, faster data acquisition capabilities, and multi-purpose potential in physical surface characterization. Using digital microscopy, fuel pellet Sa surface roughness varies in commercial reactor fuel pellets from 1.54±0.17µm to 2.11±0.12µm and does not appear to depend solely on the use of wet versus dry grinding techniques. Populations of pellets produced at three different commercial reactor fuel production facilities were distinguishable on the basis of Sa. Complementary to other key forensic characteristics, such as dimensions and enrichment, Sa measurements provide a promising nuclear forensic signature for sintered UO2 fuel pellets.