Quantifying surface roughness on UO2 fuel pellets using optical techniques

Meena Said; Charlotte W Eng; Amy E Hixon; Naomi E Marks

doi:10.1016/j.forsciint.2020.110470

Quantifying surface roughness on UO₂ fuel pellets using optical techniques

Forensic Sci Int. 2020 Nov:316:110470. doi: 10.1016/j.forsciint.2020.110470. Epub 2020 Aug 22.

Authors

Meena Said¹, Charlotte W Eng², Amy E Hixon³, Naomi E Marks²

Affiliations

¹ Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA; Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA. Electronic address: msaid@nd.edu.
² Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.
³ Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.

PMID: 32890902
DOI: 10.1016/j.forsciint.2020.110470

Abstract

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 (S_a) surface roughness measurements provide a rapid, non-destructive technique, producing efficient measurements with smaller standard uncertainties relative to 2D, arithmetic average profile (R_a) 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 S_a 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 S_a. Complementary to other key forensic characteristics, such as dimensions and enrichment, S_a measurements provide a promising nuclear forensic signature for sintered UO₂ fuel pellets.

Keywords: Fuel pellet; Microscopy; Nuclear forensics; Profilometry; Surface roughness.