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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Natural isotopic compositions of titanium, iron, and nickel observed in commercial fuel pellets – Promising candidate elements for stable isotope tagging

Stable isotope taggants would constitute unique identifiers for nuclear fuel cycle materials, resulting in expedited timelines and high confidence provenance assessments for nuclear forensics investigations. However, reliably identifying and interpreting stable isotope taggants in nuclear materials recovered from outside of regulatory control will largely be predicated on the assumption that the taggant element intrinsic to the untagged nuclear material exhibits natural isotopic ratios. Here, we present high-precision Ti, Fe, and Ni isotope compositions in 13 commercial low-enriched uranium (LEU) fuel pellets to assess the suitability of these transition metals as stable isotope taggants. Our investigations reveal limited isotope variations among the fuel pellets in all three elements, which are consistent with small mass-dependent isotope fractionations, comparable to variations previously reported for natural samples. In practice, isotopically tagged nuclear materials are expected to fall along isotopic mixing lines, since intrinsic background levels of taggant elements dilute the taggant towards natural isotope compositions. Furthermore, the observation that Ti, Fe, and Ni isotope compositions in a suite of LEU fuel pellets are close to or indistinguishable from estimates for the Bulk Silicate Earth demonstrates that a two end-member mixing assumption would be valid for these transition metals, indicating that all three are promising candidate elements for stable isotope tagging. Finally, we present mass balance calculations to quantify isotopic perturbations expected from admixing isotopically anomalous Ti, Fe, and Ni taggants to assess the interplay between elemental and taggant concentrations and find favorable compromises for facilitating successful taggant identification with current analytical methods.

Intentional forensics↗
DOE OSTI2018

Gamma spectrometry in the ITWG CMX-4 exercise

Low enriched uranium samples of unknown origin were analyzed by 16 laboratories in the context of a Collaborative Materials Exercise (CMX), organized by the Nuclear Forensics International Technical Working Group (ITWG). The purpose was to compare and prioritize nuclear forensic methods and techniques, and to evaluate attribution capabilities among participants. This paper gives a snapshot of the gamma spectrometric capabilities of the participating laboratories and summarizes the results achieved by gamma spectrometry.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Advancing nuclear forensics competencies at the National Nuclear Center of the Republic of Kazakhstan and conceptual development of a National Nuclear Forensics Library

Since 2021, the National Nuclear Center (NNC) of the Republic of Kazakhstan has been successfully developing a project dedicated to nuclear forensics. The relevance of this project is underscored by Kazakhstan’s leading position in the global uranium mining and export market. The country operates research reactors and is involved in the production of experimental nuclear fuel. The nuclear forensics project is being implemented in several key areas: the project will develop competencies in laboratory research of samples, interpretation of results, and develop a prototype concept for the National Nuclear Forensics Library. In implementing these challenges, the NNC experts draw on the experience of colleagues from world-leading scientific and research centers. Designing a prototype National Nuclear Forensics Library (NNFL) is a challenging project. In conclusion, the solution to this task is based on the IAEA’s approaches, recommendations, and the experience gained from the construction of similar systems in other countries.

and nuclear chemistry↗
DOE OSTI2020

Improved plutonium and americium photon branching ratios from microcalorimeter gamma spectroscopy

Photon branching ratios are critical input data for activities such as nuclear materials protection and accounting because they allow material compositions to be extracted from measurements of gamma-ray intensities. Uncertainties in these branching ratios are often a limiting source of uncertainty in composition determination. Here, we use high statistics, high resolution - (60–70 eV full-width-at-half-maximum at 100 keV) gamma-ray spectra acquired using microcalorimeter sensors to substantially reduce the uncertainties for 11 plutonium ( 238 Pu, 239 Pu, 241 Pu) and 241 Am branching ratios important for material control and accountability and nuclear forensics in the energy range of 125 keV to 208 keV. Lastly, we show a reduction in uncertainty of over a factor of three for one branching ratio and a factor of 2–3 for four branching ratios.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Characterizing the Thermal Column Beam in the University of Massachusetts Lowell Research Reactor

The University of Massachusetts Lowell operates a 1 MW, light water cooled and moderated Research Reactor (UMLRR) fueled by low-enriched uranium to generate neutron flux that is used at a variety of in-core and beam port facilities within the reactor to perform irradiation experiments for academic and industrial research. One of the irradiation sites is a graphite-moderated thermal column designed to deliver a collimated beam of thermal neutrons to a neutron radiography imaging system. A detailed characterization of the neutron beam is essential for the design and interpretation of experiments at the facility and for radiation safety. This work aimed to characterize the neutron flux and energy spectrum in the UMLRR thermal column beam by employing experimental and computational methods known as the foil activation and spectrum unfolding technique. A previously existing Monte Carlo N-Particle transport (MCNP) model of the UMLRR reactor core has been extended to the thermal column where the neutron flux and energy spectrum have been computed and experimentally validated. This work employed the foil activation and spectrum unfolding technique along with neutron transport computation to extend the knowledge of the neutron fluence and energy spectrum from the UMLRR core to the adjacent thermal column beam. Radiography systems are used for materials characterization, studying dynamic behavior of engineering systems, and for nuclear forensics applications. Foil activation is an experimental method where thin foils of highly pure materials are placed in the beam where interactions between the neutrons and the foil material activate radioisotopes in the foils whose activities can be measured after the irradiation. Downstream computation with MCNP and the spectrum unfolding code SAND can deconvolute the neutron fluence and energy spectrum that must have been necessary to induce the production rates of radioisotopes that were obtained through foil activation. The necessary ingredients for successful spectrum unfolding are the experimentally measured production rates and some a priori (initial guess) knowledge of the flux spectrum. The thermal column is equipped with a neutron radiography imaging system, so any experimenters who desire to use neutron radiography at UMass Lowell will benefit significantly from knowing the characteristics of the neutron beam. Comprehensive knowledge of these characteristics of the beam is essential to compare and benchmark results obtained for similar experiments at other facilities. The Integrated Nuclear Security and Safeguards Laboratory (INSSL) is pursuing the investigation of the performance of self-healing materials under stress-strain environments and the characterization of radiation detectors and special containers for storing and transporting nuclear material. This work contributes to the improvement of the current radiography system, expands the utility of the system for nuclear safeguards and security application and provides information that will enhance the general safety of the UMLRR experimental facilities. The main objective of this work has been achieved; an appropriate neutron flux spectrum for the UMLRR thermal column beam has been determined using the foil activation method followed by spectrum unfolding. There now exists an experimentally validated computational model of the neutron flux spectrum and the thermal column's neutron environment is characterized. We can conclude that the thermal column is well characterized; an appropriate neutron flux spectrum has been determined through an experimentally validated computational model. Future experimenters interested in the thermal column may now expand on the computational model or use the spectral information for their own purposes. The knowledge gained herein will be helpful for the INSSL's future work using neutron radiography to analyze the effectiveness of self-healing materials and special containers. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

Contribution of bulk mass spectrometry isotopic analysis to characterization of materials in the framework of CMX-4

Seven laboratories used the results of bulk uranium isotopic analysis by either inductively coupled plasma mass spectrometry (ICP-MS) or thermal ionization mass spectrometry (TIMS) for characterization of the samples in the Nuclear Forensic International Technical Working Group fourth international collaborative material exercise, CMX-4. Comparison of the measured isotopic compositions of uranium in three exercise samples is implemented for identifying any differences or similarities between the samples. The role of isotopic analyses in the context of a real nuclear forensic investigation is discussed. Several limitations in carrying out ICP-MS or TIMS analysis in CMX-4 are noted.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

Quantitative Encapsulation and Homogeneity Assessment of Sol–Gel Based Nuclear Explosive Debris Simulants

Nuclear explosive debris simulants are an important material in training and validating aspects of post-detonation nuclear forensic processes. Realistic simulants should replicate several aspects of nuclear explosive debris such as the size, shape, color, density, and chemical and radiological properties. Silica particles produced via sol-gel synthesis have recently been found to successfully reproduce many of these parameters including the controllable incorporation of radionuclide content. However, to be useful as a benchmarking material for validation and verification of laboratory methodologies, radionuclide content from batch-to-batch must be reproducible. Here, in this work, we explore the variance in radionuclide distribution incorporated into sol-gel benchmarking materials with respect to sample subdivision. Results will help inform the sample sizes required to minimize variance between samples.

36 - MATERIALS SCIENCE↗
DOE OSTI2019

Actinide Isotopic Analysis by Atomic Beam Laser Absorption Spectroscopy

The isotopic analysis of nuclear materials in the field has important applications in nuclear forensics for non-proliferation. In the area of safeguards, the rapid detection of isotopic signatures and ratios of uranium and plutonium reveals whether or not nuclear materials are as declared for a given facility.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Application of modern autoradiography to nuclear forensic analysis

Modern autoradiography techniques based on phosphorimaging technology using image plates (IPs) and digital scanning can identify heterogeneities in activity distributions and reveal material properties, serving to inform subsequent analyses. Here, we have adopted these advantages for applications in nuclear forensics, the technical analysis of radioactive or nuclear materials found outside of legal control to provide data related to provenance, production history, and trafficking route for the materials. IP autoradiography is a relatively simple, non-destructive method for sample characterization that records an image reflecting the relative intensity of alpha and beta emissions from a two-dimensional surface. Such data are complementary to information gathered from radiochemical characterization via bulk counting techniques, and can guide the application of other spatially resolved techniques such as scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). IP autoradiography can image large 2-dimenstional areas (up to 20 × 40 cm), with relatively low detection limits for actinides and other radioactive nuclides, and sensitivity to a wide dynamic range (10 5 ) of activity density in a single image. Distributions of radioactivity in nuclear materials can be generated with a spatial resolution of approximately 50 μm using IP autoradiography and digital scanning. While the finest grain silver halide films still provide the best possible resolution (down to ~10 μm), IP autoradiography has distinct practical advantages such as shorter exposure times, no chemical post-processing, reusability, rapid plate scanning, and automated image digitization. Sample preparation requirements are minimal, and the analytical method does not consume or alter the sample. These advantages make IP autoradiography ideal for routine screening of nuclear materials, and for the identification of areas of interest for subsequent micro-characterization methods. Here in this article we present a summary of our setup, as modified for nuclear forensic sample analysis and related research, and provide examples of data from select samples from the nuclear fuel cycle and historical nuclear test debris.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2019

Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics

Until recently, the analysis and identification of nuclear fuel pellets in the context of a nuclear forensics investigation have been mainly focused on macroscopic characteristics, such as fuel pellet dimensions, uranium enrichment, and other reactor-specific features. Here, we report microscale isotopic heterogeneity observed in different fuel pellet fragments that were characterized in situ by nanoscale secondary ion mass spectrometry (NanoSIMS). The materials analyzed include fuel fragments obtained as part of the Collaborative Materials Exercise (CMX-4) organized by the Nuclear Forensics International Technical Working Group (ITWG), as well as a fuel pellet fragment from a commercial power reactor. Although the commercial fuel pellet showed a homogeneous 235 U/ 238 U ratio across the sample (within analytical error), NanoSIMS imaging of the CMX-4 fuel pellet fragments showed distinct microscale variations in the uranium isotopic composition. The average 235 U enrichments were 2.2 and 2.9% for the two samples; however, the measured 235 U/ 238 U ratios varied between 0.0081 and 0.035 (0.79–3.3 atom % 235 U) and between 0.0090 and 0.045 (0.89–4.3 atom % 235 U). The measurement of 236 U in one of the CMX-4 samples suggested the use of at least three uranium oxide powders of different isotopic compositions (“source terms”) in the production of the pellets. These variations were not detected using the conventional bulk, macroscopic techniques applied to these materials. Furthermore, our study highlights the importance of characterizing samples on the microscale for heterogeneities that would otherwise be overlooked and demonstrates the potential use of NanoSIMS in guiding further nuclear forensic analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

National nuclear forensics libraries: a case study on benefits and possibilities for identification of sealed radioactive sources

A National Nuclear Forensic Library (NNFL) is a useful nuclear forensics tool which consists of information and subject matter expertise on radioactive and nuclear (RN) materials produced, used or stored within a State. If RN material is found out of regulatory control the NNFL can be used as part of a nuclear forensics investigation to help identify whether or not the material is consistent with a country’s national holdings. In previous work, a number of signatures which can be useful to identify sealed sources of 241 Am were investigated. To validate the measurement results, an official query concerning information about two of the previously investigated 241 Am sources was sent to the United States Department of State, the international point-of-contact (POC) for the U.S. NNFL. The aim of this work is to show how data obtained in a characterization of a radioactive source can be used in conjunction with an NNFL to investigate the history of a source out of regulatory control.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

Development of small particle speciation for nuclear forensics by soft X-ray scanning transmission spectromicroscopy

Synchrotron radiation spectromicroscopy provides a combination of submicron spatial resolution and chemical sensitivity that is well-suited to analysis of heterogeneous nuclear materials. The chemical and physical characteristics determined by scanning transmission X-ray microscopy (STXM) are complementary to information obtained from standard radiochemical analysis methods. In addition, microscopic quantities of radioactive material can be characterized rapidly by STXM with minimal sample handling and intrusion, especially in the case of particulate materials. The STXM can accommodate a diverse range of samples including wet materials, complex mixtures, and small quantities of material contained in a larger matrix. In these cases, the inventory of species present in a sample is likely to carry information on its process history; STXM has the demonstrated capability to identify contaminants and sample matrices. Operating in the soft X-ray regime provides particular sensitivity to the chemical state of specimens containing low-Z materials, via the K-edges of light elements. In this paper, recent developments in forensics-themed spectromicroscopy, sample preparation, and data acquisition methods at the Molecular Environmental Science Beamline 11.0.2 of the Advanced Light Source are described. Results from several initial studies are presented, demonstrating the capability to identify the distribution of the species present in heterogeneous uranium-bearing materials. Finally, future opportunities for STXM forensic studies and potential methodology development are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Nuclear fuel irradiation testbed for nuclear security applications

The nuclear security community has long been interested in the identification and quantification of nuclear material signatures to understand a material’s provenance, use, and ultimate application. New forensics signatures and methods intended for non-traditional or advanced nuclear fuel applications require fuel irradiation experiments to demonstrate viability and validity. Integral fuel irradiations have historically required significant costs and long timelines to design, irradiate, and characterize. This paper describes how a recently developed nuclear fuel irradiation testbed can be used to provide a low cost, rapid turnaround, modular test environment for irradiation and evaluation of nuclear fuel specimens for nuclear security applications. The irradiation testbed houses six small ‘MiniFuel’ samples within hermetically sealed capsules inside targets that can be removed in between each ∼25-day operating cycle of the High Flux Isotope Reactor (HFIR). As many as nine targets can be irradiated using a single irradiation position (reflector region) in HFIR, allowing for varying irradiation temperatures and burnups. A suite of hot cell capabilities have been established to perform post-irradiation examination for measuring performance (e.g., fuel swelling, fission gas release) and facilitating experiment disassembly for subsequent property measurements, microstructural analysis, or chemical assay. This new testbed allows fuel irradiations to be conducted on an accelerated timeframe to enable rapid proof of concept testing and to provide reference material for nuclear fuel security applications. Recent applications using this testbed include the testing of isotopic taggants in UO 2 fuel (intentional forensics), testing of U-10Mo fuel for down-conversion of highly enriched uranium–fueled reactors, and the production of irradiated UO 2 fuel material for signature analysis of its isotopic composition (plutonium, fission gases, etc.).

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2016

National technical nuclear forensics: history and U.S. research priorities

In the event of a nuclear detonation in the United States, the interdiction of a nuclear device, or the seizure of nuclear materials, there will be tremendous pressure to attribute the source, establish responsibility, and ensure the prevention of a subsequent incident. The U.S. response to any attack will have to be backed up by demonstrable proof. Nuclear forensics contributes to this demonstrable proof by helping to identify the type of weapon and nuclear material used and where it came from. Nuclear forensics is the collection, analysis, and evaluation of pre-detonation (intact) and post-detonation (exploded) radiological or nuclear materials, devices, and debris, as well as the immediate effects created by a nuclear detonation. Along with intelligence and law enforcement investigations, nuclear forensics stands as one of the three pillars supporting attribution. To ensure the nation's readiness to execute the mission, the National Technical Nuclear Forensics (NTNF) Interagency, which include the Departments of Homeland Security, Defense, Energy, Justice, and State and the Office of the Director of National Intelligence, is consistently focused on improving its analytical capabilities by continually assessing and enhancing the accuracy, precision, and timeliness of NTNF relevant conclusions, while ensuring the quality of those conclusions. This focus drives the Inter-agency's Research and Development priorities, which are divided into four key technical mission areas (TMA). The TMAs span the spectrum of the NTNF enterprise, from pre- to post- detonation, and guide agency funding decisions. (authors)

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2022

Age determination of a 75 Se gamma radiography source for nuclear forensics

Here, two methods were used to evaluate the age of 75 Se sealed source material. Both methods utilized gamma spectroscopy to determine the quantity of parent 75 Se present, but they differed in the technique used to determine the quantity of daughter 75 As. In one method, 75 As was quantified using inductively coupled plasma-mass spectrometry (ICP-MS) after using chromatographic techniques to separate the parent and daughter isotopes. In the other method, total As was measured using optical emission spectroscopy (OES), which did not require separation prior to measurement. The OES method was faster and gave slightly lower uncertainties, but required more daughter material to be present because of higher concentration requirements, making it unsuitable for young material. Both methods are hampered by the monoisotopic nature of As, but still gave reasonable model ages that were in agreement with each other.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Qualification and initial characterization of a high-purity 233 U spike for use in uranium analyses

Several high-purity 233 U items potentially useful as isotope dilution mass spectrometry standards for safeguards, non-proliferation, and nuclear forensics measurements are identified and rescued from downblending. By preserving the supply of 233 U materials of different pedigree for use as source materials for certified reference materials (CRMs), it is ensured that the safeguards community has high quality uranium isotopic standards required for calibration of the analytical instruments. One of the items identified as a source material for a high-purity CRM is characterized for the uranium isotope-amount ratios using thermal ionization mass spectrometry (TIMS). Additional verification measurements on this material using quadrupole inductively coupled plasma mass spectrometry (ICPMS) are also performed. As a result, the comparison of the ICPMS uranium isotope-amount ratios with the TIMS data, with much smaller uncertainties, validated the ICPMS measurement practices. ICPMS is proposed for the initial screening of the purity of items in the rescue campaign.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Surrogate Post-Detonation Urban Debris (SPUD): Standard Reference Materials 4600 and 4601

If a terrorist nuclear explosion were to occur in the United States, high-quality (accurate and precise) legally defensible nuclear forensics measurements will be required to assure the certainty and confidence needed, for conclusions drawn from these data will be coupled with law enforcement and intelligence information for the purposes of attribution and retribution. Standard Reference Materials (SRMs)/Certified Reference Materials (CRMs) establish the traceability, accuracy, and precision of nuclear forensic measurements and provide the ability to benchmark measurement methods essential to meeting the requirements of legal scrutiny. Currently there is a critical shortage of key SRMs/CRMs required for accurate and precise measurements that are fundamental to nuclear measurements supporting pre- and post-detonation nuclear forensics. Supplies either do not exist, are not good enough, are in short supply, and/or are very expensive. The radionuclide measurement techniques and data quality objectives for pre- and post-detonation nuclear forensics are quite different than the applications for which the current suite of available SRMs/CRMs was developed. Specifically, 1) modern mass spectrometry methods have largely replaced traditional activity-based measurement methods for quantifying small quantities of long-lived radionuclides and most trace radionuclide SRMs/CRMs are certified for activity and are thus not adequate for current applications, 2) modern instrumental methods are capable of higher precision than historic measurement techniques, and in some cases exceed the precision of the available SRMs/CRMs, and 3) the quality assurance requirements for pre- and post-detonation nuclear forensics are such that the existing cadre of SRMs/CRMs does not adequately support the needs for method validation. There are numerous governmental stakeholders both within the US (DOE, DoD) and internationally (IAEA, JRC-ITU) whose missions are either directly involved with nuclear forensics measurements or rely on the forensic data obtained to make the exacting policy decisions (DOJ (FBI), DHS, CIA, DIA, DoD) associated with disrupting the production of illicit nuclear materials, interdicted nuclear materials or a nuclear/radiological detonation event. Starting in 2008 the DHS NTNFC, in collaboration with NBL and NIST, took on the production of suitable SRMs/CRMs for the pre-detonation nuclear forensics community. Two CRMs have been released since the start of this effort and two more are slated for completion in 2016. More recently, NIST, as a part of its mission as the US National Metrology Institute (NMI) to deliver standards (providing traceability) and foster homeland security, has launched the first certification campaign of a measurement traceable post nuclear detonation SRM. NIST, in cooperation with partner labs (AFIT (DoD), FBI (DOJ), and NPL) and with support from the FBI, has developed two Surrogate Post-Detonation Urban Debris (SPUD) Standard Reference Materials (SRMs) - SRM 4600 and 4601. These SRMs have been developed to simulate the expected debris mixture from the detonation of an Improvised Nuclear Device (IND) in an urban environment, which is capable of producing fresh fission as well as activation products. The elemental composition of the vitrified debris materials is a composite of minerals and metals characteristic of the concrete and steel, the building materials that would be exposed to a nuclear detonation and whose resulting activation products would be found in rubble samples collected for forensics evidence and attribution. Additionally, because post-detonation samples would also contain short-lived fission products, the debris materials have been doped with Uranium (U). To create the nuclear fission products, samples of the SPUD materials can be placed in a well-characterized nuclear reactor and exposed to a set neutron flux and energy, causing the encased U atoms to split and yield short-lived fission products. Because a known amount of U is added to the SPUD materials it is feasible to determine the concentration of the resulting fission products. The subsequent irradiated SPUD glass would be chemically similar to samples that would be generated in an actual detonation, and thus can serve as a standardized reference material for nuclear forensic post detonation measurements. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗