The precision and accuracy of a Revvity 6220 GCT Liquid Scintillation Counter (LSC) was tested with a certified tritiated water standard and using a combination of variables including vial type, cocktail selection, and quench curve parameters. Differences in the vial and cocktail choice used for quench measurements and samples were shown to drastically affect the accuracy of the tritium activity measured. Additionally, chemical-based and urine-based quench curves were generated to most closely match the sample matrices analyzed for bioassay samples. Lab generated quench curves designed for programmatic samples performed with improved accuracy compared to commercially available quench standards.

This paper explores the feasibility of using U–Th isochrons as a tool to help interpret 230Th–234U model ages derived from uranium metal samples. We introduce the basic concepts of the isochron, including the conditions required to produce a meaningful isochron from U–Th isotope data. Then, using examples from cast uranium metal samples, show how isochrons can be used to guide our understanding of the assumption of purification in a 230Th–234U model-age, and provide additional age data that can used to aid nuclear forensic investigations.

We have developed an alpha spectrometry method for 230Th/234U radiochronometry to determine the model separation age for uranium materials. This method offers an alternative to the more commonly used, but significantly more resource intensive multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) while providing similar accuracy and precision. The development included radiochemical separation of uranium and thorium, calibration of the 232U tracer and the alpha spectrometry measurement. The method was validated by analyzing a certified reference material, CRM 125-A, which is a uranium oxide pellet assay, isotopic, and radiochronometric standard. The results were compared to those obtained by our routine MC-ICP-MS 230Th/234U radiochronometry analysis method to assess the performance parameters for alpha spectrometry compared to the state-of-the-art technique.

This case study from the in-vitro bioassay program of the Los Alamos National Laboratory (LANL) demonstrates the importance of analyte-tracer equilibrium when determining plutonium (Pu) using isotope dilution methods. The program utilizes externally produced urine QC materials spiked with known quantities of Pu isotopes to validate performance. In early 2019, we started observing a significant low bias between measured and expected results for the QC samples, and as part of an investigation into the root cause, conducted a study into tracer—analyte equilibrium chemistry. During the study, we also uncovered that a contributing cause of the low bias was the use of a new urine donor that had a high EDTA diet, which was likely complexing Pu in the urine QC samples. A modified radiochemistry procedure that more effectively destroys the EDTA-Pu complex and ensures equilibrium between tracer and analyte Pu was validated.

Understanding the dissolution behavior of ThO2 in pulmonary environments is critical for evaluating biokinetic behavior and estimating internal dose from inhalation. We developed a computational model to simulate ThO2 dissolution in simulated lung fluid, emphasizing the effects of particle age and α-recoil-induced damage. The model integrates particle geometry, defect generation, and surface reactivity to predict time-dependent dissolution across short to long durations. Simulations show rapid initial dissolution followed by passivation, with aged particles exhibiting enhanced early solubility. Benchmarking against in-vitro data demonstrates the utility of in silico tools for predicting actinide-oxide dissolution when experimental data are limited.

The model age of a nuclear material is crucial in nuclear forensic analysis. Uranium metals with complex production histories often exhibit discordant model ages from the 230Th–234U and 231Pa–235U chronometers. Recent studies involving targeted uranium metal castings have enhanced our understanding of decay product behavior during casting, aiding nuclear forensic interpretation. Building on this prior work, forensics laboratories at Atomic Weapons Establishment (AWE), Lawrence Livermore National Laboratory (LLNL), and Los Alamos National Laboratory (LANL) conducted an interlaboratory comparison to investigate spatial heterogeneity in uranium metal cast under controlled conditions. Each laboratory measured samples of a mixed feedstock and its corresponding cast product. This work furthers our understanding of discordant model ages and the use of discordance as a signature to enhance confidence in interpretations of radiochronometric data for nuclear forensics.

Uranium isotopic composition can provide valuable information about the history and provenance of a nuclear material; therefore, uranium isotopic analyses are frequently made in the nuclear forensics, safeguards, and environmental monitoring communities. These measurements have always presented challenges due to the extreme variability in the relative abundance between the major (U-235, U-238) and minor (U-233, U-234, U-236) isotopes of uranium. The recently developed ATONA (Atto- to Nano-Amp) amplification system paired with Faraday cup detectors has a large dynamic range and low noise floor making it ideal for measuring uranium isotopic ratios in materials of both natural and anthropogenic origin. A wide variety of certified reference materials were analyzed to investigate the utility of the ATONA amplification system for determining uranium isotopic composition in samples ranging from depleted to highly enriched. The ATONA amplifiers provide nearly an order of magnitude improvement in external reproducibility over 10(11) Omega amplifiers when measuring the minor U-234/U-238 ratio in isotopically natural and depleted samples and when paired with a secondary electron multiplier can measure very low relative abundance uranium isotopes (i.e., U-236).

A radioanalytical method was developed for the determination of trace plutonium and neptunium in samples composed primarily of uranium. The procedure uses a neodymium oxalate co-precipitation and a two-column separation using ion exchange resin to achieve high uranium decontamination, high plutonium and neptunium separation factors and low impurity levels. The separation of the three actinides from each other relies on their oxidation–reduction chemistry. Various measurement techniques can be applied to determine plutonium and neptunium in the purified fractions: i.e., alpha spectrometry, and thermal ionization mass spectrometry. The method development, validation, and applications are discussed.

Radiochronometry provides the model age of nuclear materials, which is useful for understanding the production history of materials found outside of regulatory control. Certified reference materials (CRMs) are important for radiochronometry to increase confidence in measurement quality; however, the absence of 231Pa/235U CRMs necessitates that nuclear forensic laboratories measure the 231Pa/235U model ages of preexisting uranium reference materials. Here, new consensus 231Pa/235U model ages are reported from three nuclear forensic laboratories for three reference materials using current analytical methods. These updated consensus values can be used for quality control of 231Pa/235U model age measurements.

materials is then discussed, with an emphasis on improvements in accuracy that have been gained from measurements of multiple radioisotopic systems. Finally, papers that report on casework are reviewed, to provide a window into current scientific practice.

We present a chromatography chemistry for purifying protactinium from uranium metal alloys containing weight-percent concentrations of niobium. Niobium is precipitated in 9 M HCl without the co-precipitation of Pa as demonstrated by gamma-ray spectrometry. Protactinium is further purified using Bio-Rad™ anion resin AG® 1-X8 and 9 M HCl + 0.0128 M HF. A Pa/Nb separation factor of 85,000 and a 90% Pa recovery is demonstrated, which is amenable to 231Pa concentration determination by isotope dilution and 231Pa/235U model age calculation for nuclear forensics.

Particulate isotopic analysis in nuclear forensics has developed rapidly during the past two decades due to technical advances in determining the isotopic composition of individual particles. This paper introduces basic statistical concepts that can be applied by analysts to understand the importance of statistical adequacy when interpretating particle data. While these basic statistical methods provide a useful point-of-entry to particle data analysis, more sophisticated statistical and modeling approaches are needed to extract maximal information from such datasets in the future.

We present a combined TEVA-DGA chromatography chemistry to purify single-element fractions of Pu, Am, and Np from bulk (mg-level) U materials. Plutonium and Np are first sorbed onto TEVA resin using a 4 + redox adjustment with a hydroxylamine hydrochloride and sodium nitrite treatment, with U + Am eluting directly onto DGA resin. Americium is then purified from U on DGA using 0.1 M HNO 3 as a U eluent. A subsequent TEVA column is used to separate Pu from Np using hydrogen peroxide to oxidize Np into the 5 + oxidation state for elution through TEVA. Our presented TEVA-DGA method is able to produce high-purity, single-element fractions of Pu (90% recovery), Am (98% recovery), and Np (62% recovery) from mg-levels of U, and does so in three days of column chemistry.

A nuclear forensics investigation involving a uranium ore concentrate relies on accurate and precise analysis of impurities. Analytical data defensibility requires the use of reference materials as part of quality control. This study presents a compilation of trace element concentration results of the CUP-2 Uranium Ore Concentrate Standard measured by 11 different laboratories. The laboratories employed various dissolution methods, analytical preparation methods, and instrumental platforms. The data presented here contain concentrations of 66 impurities with up to 138 individual data points for each impurity. Consensus values have been assigned to each impurity following a statistical analysis of the data set.

In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable 137 Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension.

Improved methods employed at Los Alamos National Laboratory for 231 Pa/ 235 U radiochronometry are outlined. We present elution curves obtained during 233 Pa tracer preparation from 237 Np. Additionally, we report model ages for uranium certified reference materials (CRMs) exhibiting a range of 235 U enrichments including the first 231 Pa/ 235 U model ages for CRMs U200 and U900. Our results enable these CRMs to be used, with increased confidence, as quality control materials during nuclear forensics investigations.

The plutonium rapid response in vitro bioassay method described here was designed to determine 238Pu, 239Pu, and 240Pu concentration in urine samples from workers with potential internal contamination. Results provide quick and actionable information about the level of contamination necessary to assist making further medical decisions, including chelation therapy. The radiochemical procedure can be performed within approximately 48 h, including sample preparation, measurement(s) by alpha spectrometry and/or inductively coupled plasma mass spectrometry (ICP-MS), and data evaluation.

Journal Article Identification and Particle Size Determination of 238Pu-bearing Particles via Alpha Spectrometry, Autoradiography and Scanning Electron Microscopy Get access Kimberly Wurth, Kimberly Wurth Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Benjamin Naes, Benjamin Naes Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Travis Tenner, Travis Tenner Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Lisa Hudston, Lisa Hudston Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Zsuzsanna Macsik, Zsuzsanna Macsik Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Mike Harris, Mike Harris Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Robert Steiner, Robert Steiner Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Stephen LaMont Stephen LaMont Los Alamos National Laboratory – C-NR, Los Alamos, New Mexico, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 914–917, https://doi.org/10.1017/S1431927622004020 Published: 01 August 2022

This work demonstrates an analytical protocol for high precision Sm isotope analysis by thermal ionization mass spectrometry (TIMS) using a Pt activator. The method permits precise measurements of small aliquots (1–20 ng) of Sm on single Re filament using a modified static-total evaporation technique. This study represents the first attempt to use such protocols for Sm isotope analyses while reducing the loading size of Sm for TIMS. The method could potentially be deployed to study geological, meteorites and lunar samples containing low Sm concentrations, to monitor neutron irradiation exposure based on 149,150Sm, or to measure Sm isotopic composition in other types of nuclear samples.