Development of an Aerosol-Based Method for the Manufacture of Surrogate
Environmental Test Swipes

The analysis of environmental test swipes laden with actinide-bearing particles is a key component of treaty verification activities and nuclear safeguards inspections. The frequency and importance of these analyses has resulted in the need for high-quality reference materials with known particle loadings and compositions for use in proficiency testing, interlaboratory comparisons, and method development. Recent advancements towards the manufacture of actinide-bearing microparticulates including the THermally Evaporated Spray for Engineered Uniform particulateS (THESEUS) production platform, developed at Savannah River National Laboratory (SRNL), have resulted in the availability of highly uniform uranium-bearing particulate reference materials with tailored isotopic compositions in quantities ranging from nanograms to milligrams. However, the availability of suitable particle-laden test swipes has lagged. To expand this particulate generation capability to include particle-laden test swipes, the settling behavior of aerosolized particles within a static volume of air was leveraged to develop a capability for the manufacture of swipes with tailorable and uniform particle loading in conjunction with the THESEUS particle production platform. The developed method was tested using depleted uranium oxide particles, with 1-micron equivalent circular diameter, to produce batches of particle-laden swipes with varying particulate loadings. Total uranium content of the generated swipes was measured using kinetic phosphorescence analysis (KPA), and the preservation of the particulate qualities through the manufacturing process was assessed using scanning electron microscopy (SEM) as well as large geometry secondary ion mass spectrometry (LG-SIMS). Assessments of inter-swipe uniformity suggest good agreement of particle loading both within and between batches, with variation between swipes below 15% in most scenarios, as measured by KPA. Furthermore, the developed capability displays a high degree of tailorability in the particle dosing on a per-swipe basis, with a linear relationship including demonstrated loadings ranging from tens of nanograms to tens of micrograms of uranium per-swipe. The developed method for the generation of particleladen test swipes displays promise for the future manufacture of reference surrogate environmental swipe specimens, and is expected to enable both future proficiency tests, as well as development and evaluation of particle extraction techniques.