Analysis Of Nuclear Materials Research Articles

Introduction to Nuclear Forensics Analysis Techniques

Abstract Nuclear forensics is the interdisciplinary branch of forensic science that deals with the analysis and examination of nuclear or other radioactive materials, or of evidence that is contaminated with radionuclides in the context of legal proceedings under international or national law related to nuclear security. To control and avoid the threat of terrorism posed by illicit trafficking and mismanagement, nuclear and other radioactive materials must be strictly regulated. Thus, the goal of nuclear forensic analysis is to discover what radioactive materials were confiscated, how, when, and where they were manufactured, and what their intended applications were. Nuclear forensic scientist has a wide array of analytical tools to use for detecting signatures in radioactive materials. These individual techniques can be sorted into three broad categories: bulk analysis tools, imaging tools, and micro-analysis tools. Particular interest in nuclear forensics is particle morphology, isotopic composition of a material, presence of impurities, and microstructure. These properties can vary between materials of different origins due to varying processing or geological conditions, thus, allowing for discrimination of material history and prediction of provenance. This review article presents many key analytical techniques and discusses the main application and challenges of the most common techniques currently used in nuclear forensics analysis.

Spatially Resolved Raman Spectroscopic Investigation of Uranyl Fluoride: A Case Study in the Importance of Instrument Optimization.

Raman spectroscopy is an emerging technique for rapid and nondestructive analysis of nuclear materials for forensic and nonproliferation applications as it is a powerful tool for distinguishing multiple chemical forms of materials with similar stoichiometries. Recent developments in spectroscopic software have enabled rapid data collection with high-speed Raman spectroscopic mapping capabilities. However, some uranium-rich materials are susceptible to degradation in humid air and/or laser-induced phase transformations. To mitigate environmental or measurement-related sample degradation of potential samples of interest, we have taken a systematic approach to define optimized data collection parameters for high-throughput measurements of uranyl fluoride (UO2F2), which is an important intermediate material in the nuclear fuel cycle. First, we systematically describe the influence of optical magnification (5× to 100×), laser power, and exposure time on obtained signal for identical particles of UO2F2 and find that at low laser power and exposure times, comparable signal is obtained regardless of optical magnification. Second, we ensure sample integrity during data collection, and third, collect spectroscopic maps that employ optimized parameters to reduce the time required to obtain spatially resolved spectroscopic information. Reductions of 90% and 99% in measurement times are discussed as they relate to differences in resolving spectroscopic features of particles in identical mapping areas. During this work, we found that additional data processing options were needed and thus developed a customized Python script for importing, processing, analyzing, and visualizing Raman spectroscopic map data.

Production of negative ion beams through charge transfer between negative hydrogen ion beams and non-metallic gases

Negative ion beam applications in tandem accelerators are used for nuclear research, environmental studies, materials analysis, medical treatments, and ion implantation in semiconductor devices. Conventional methods for generating negative ions for tandem accelerators rely on metallic vapors (typically alkali) for charge exchange, which pose challenges like contamination, electrical shorting and breakdowns, and maintenance issues. To address these drawbacks, this work explores an alternative approach to produce negative ions using a non-metallic charge exchange process. It involves directing negative hydrogen ions into neutral gases within a specially designed charge exchange cell equipped with an electrostatic accelerator. The method is applied to various gas targets, including He, H2 and O2, to accelerate and measure resulting negative ions. This innovative approach aims to mitigate contamination concerns associated with metallic vapor double-charge exchange methods and explore novel avenues for negative ion production through charge transfer. Any newly formed negative ion beam current conversion ratios from the incident H− beam will be reported as progress in this research.

Improving uranium oxide pathway discernment and generalizability using contrastive self-supervised learning

In the field of Nuclear Forensics, there exists a plethora of different tools to aid investigators when performing analysis of unknown nuclear materials. Many of these tools offer visual representations of the uranium ore concentrate (UOC) materials that include complimentary and contrasting information. In this paper, we present a novel technique drawing from state-of-the-art machine learning methods that allows information from scanning electron microscopy images (SEM) to be combined to create digital encodings of the material that can be used to determine the material’s processing route. Our technique can classify UOC processing routes with greater than 96% accuracy in a fraction of a second and can be adapted to unseen samples at similarly high accuracy. The technique’s high accuracy and speed allow forensic investigators to quickly get preliminary results, while generalization allows the model to be adapted to new materials or processing routes quickly without the need for complete retraining of the model.

Morphology of uranium oxides reduced from magnesium and sodium diuranate

Abstract Morphological analysis of uranium materials has proven to be a key signature for nuclear forensic purposes. This study examines the morphological changes to magnesium diuranate (MDU) and sodium diuranate (SDU) during reduction in a 10 % hydrogen atmosphere with and without steam present. Impurity concentrations of the materials were also examined pre and post reduction using energy dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM-EDX). The structures of the MDU, SDU, and UO x samples were analyzed using powder X-ray diffraction (p-XRD). Using this method, UO x from MDU was found to be a mixture of UO2, U4O9, and MgU2O6 while UO x from SDU were combinations of UO2, U4O9, U3O8, and UO3. By SEM, the MDU and UO x from MDU had identical morphologies comprised of large agglomerates of rounded particles in an irregular pattern. SEM-EDX revealed pockets of high U and high Mg content distributed throughout the materials. The SDU and UO x from SDU had slightly different morphologies. The SDU consisted of massive agglomerates of platy sheets with rough surfaces. The UO x from SDU was comprised of massive agglomerates of acicular and sub-rounded particles that appeared slightly sintered. Backscatter images of SDU and related UO x materials showed sub-rounded dark spots indicating areas of high Na content, especially in UO x materials created in the presence of steam. SEM-EDX confirmed the presence of high sodium concentration spots in the SDU and UO x from SDU. Elemental compositions were found to not change between pre and post reduction of MDU and SDU indicating that reduction with or without steam does not affect Mg or Na concentrations. The identification of Mg and Na impurities using SEM analysis presents a readily accessible tool in nuclear material analysis with high Mg and Na impurities likely indicating processing via MDU or SDU, respectively. Machine learning using convolutional neural networks (CNNs) found that the MDU and SDU had unique morphologies compared to previous publications and that there are distinguishing features between materials created with and without steam.

An irradiation system for nuclear and materials research in a medical cyclotron

Development and commissioning of an irradiation system and experimental setup for nuclear research and materials analysis in a medical cyclotron facility is described. The setup, Low Energy in-Vacuum Irradiation System-LEVIS, is installed at the end of the existing R&D beamline. The components of LEVIS and their functions are explained and the characteristics such as energy, current and profile of the beam are measured. Different types of radiation detectors are installed and tested in the chamber for future applications of non-destructive analysis methods.

Study of Tl-based perovskite materials TlZX3 (Z = Ge, Sn, Be, Sr; X = Cl, Br, I) for application in scintillators: DFT and TD-DFT approach

Scintillators are designed significantly for utilization in a broad range of technology fields, notably nuclear physics, healthcare testing, and materials analysis. A number of applications involving scintillators, such as therapeutic image analysis, burglary prevention as well and nuclear investigation, have tempted scientists to establish novel and effective scintillators. In this report, thallium-based perovskite material TlZX3 (Z = Ge, Sn, Be, Sr; X = Cl, Br, I) has been examined by means of DFT and TD-DFT approaches. The structural, electronic, optical, and thermal properties of TlZX3 are calculated and discussed. The HOMO-LUMO energy gap of TlGeX3, TlSnX3, TlBeX3, and TlSrX3 are found in the range of 1.76 eV to 2.12 eV, 1.77 eV to 2.27 eV, 1.56 eV to 2.04 eV and 1.06 eV to 2.81 eV, respectively. Lattice constant, unit cell volume, formation energy, VEA, electrophilicity index, polarizability, refractive index, dielectric constant, entropy, and heat capacity of TlZX3 increase gradually from Cl to Br to I. However, HOMO-LUMO energy gap, tolerance factor, dipole moment, optical electronegativity, thermal energy, ZVPE, and Gibbs energy drop down from Cl to Br to I. Among the studied materials, TlGeI3 shows the maximum value of molecular hardness and electronegativity while TlSrCl3 exhibits the minimum value. The computed HOMO-LUMO energy gap and refractive index of the studied materials are in close agreement with the previously reported findings, it specifies their potential application in scintillator and solar cells.

Total Reflection Xray Fluorescence (TXRF) spectrometry as a powerful and broad-spectrum analytical tool in the nuclear sciences

X-ray spectroscopy is widely used in nuclear reaction and structure studies. To aid such studies the technological envelope is continually being pushed to achieve higher quality such as superior power and brilliance, higher resolution and sensitivity. We present the discussion of a relatively new form of X-ray fluorescence spectrometry - Total Reflection X-ray Fluorescence (TXRF) spectrometry that can achieve analytical sensitivities of the order of parts per billion (ppb). An overview of the TXRF technique is presented and its utility for nuclear materials analysis discussed. Polarized Energy Dispersive X-ray Fluorescence (PEDXRF) spectrometry is also an XRF technique that can complement TXRFS where it may not be applicable. That scenario is discussed with respect to our results using PEDXRF on geothermal samples that serve to corroborate the recent findings of the Borexino Geoneutrino Experiment regarding the high Th, U concentrations in the earth’s mantle.

Challenges in correlating oxygen stable isotope ratios of hydrates on uranium ore concentrates to process waters

Abstract Exchange of oxygen stable isotopes (δ18O values) between precipitation waters and uranium oxides is governed by thermodynamics or kinetics. It has been assumed that meteoric waters can be related to precipitation waters in uranium ore concentrates and their calcined and reduced uranium oxide products. With this assumption, the δ18O values of uranium materials could provide forensic signatures that identify the production history and geolocation of nuclear materials. To further exploit the potential of δ18O values in nuclear material analysis, this study examines the oxygen stable isotope exchange in two UOCs, magnesium diuranate (MDU) and sodium diuranate (SDU). MDU and SDU were synthesized from solutions of uranyl nitrate hexahydrate using precipitation waters with unique oxygen isotope compositions. The structures of the MDU and SDU were analyzed using powder X-ray diffraction (p-XRD) and thermal mass loss curves, while the δ18O values of waters generated during thermal decomposition were analyzed using a thermogravimetric analyzer coupled to an isotope ratio infrared spectrometer (TGA-IRIS). By p-XRD, the MDU was uniform and amorphous across all syntheses with residual crystalline material incorporated as a minor component. Combined with the TGA results, all of the MDU is likely amorphous MgU2O7·3H2O with MgO impurities present throughout. In contrast, the SDU synthesis resulted in multiple phases with many samples exhibiting crystalline phases including a combination of Na(UO2)4O2(OH)5·5H2O and Na2(UO2)6O4(OH)6·8H2O with a Na2U2O7 minor phase. A small fraction of the SDU samples were amorphous with no crystalline XRD peaks observed. Mass loss curves of the SDU samples revealed that the amorphous samples contained inclusions of similar crystalline phases compared to the crystalline materials. The uniformity of the MDU samples enabled highly reproducible measurements of δ18O values of the water vapor yielded from two dehydration events at 170 °C and 500 °C. In contrast, the multiphase composition of the SDU samples resulted in poor reproducibility in δ18O values. Neither system revealed any correlation between the δ18O values of precipitation water and the waters released during dehydration of the UOCs.

Machine learning in analytical spectroscopy for nuclear diagnostics [Invited

Analytical spectroscopy methods have shown many possible uses for nuclear material diagnostics and measurements in recent studies. In particular, the application potential for various atomic spectroscopy techniques is uniquely diverse and generates interest across a wide range of nuclear science areas. Over the last decade, techniques such as laser-induced breakdown spectroscopy, Raman spectroscopy, and x-ray fluorescence spectroscopy have yielded considerable improvements in the diagnostic analysis of nuclear materials, especially with machine learning implementations. These techniques have been applied for analytical solutions to problems concerning nuclear forensics, nuclear fuel manufacturing, nuclear fuel quality control, and general diagnostic analysis of nuclear materials. The data yielded from atomic spectroscopy methods provide innovative solutions to problems surrounding the characterization of nuclear materials, particularly for compounds with complex chemistry. Implementing these optical spectroscopy techniques can provide comprehensive new insights into the chemical analysis of nuclear materials. In particular, recent advances coupling machine learning methods to the processing of atomic emission spectra have yielded novel, robust solutions for nuclear material characterization. This review paper will provide a summation of several of these recent advances and will discuss key experimental studies that have advanced the use of analytical atomic spectroscopy techniques as active tools for nuclear diagnostic measurements.

Development and Calibration of Thermoelectric-Power-Based Non Destructive Evaluation (TNED) Device for Aging Analysis of Carbon Steel SA 106B

The aging analysis of nuclear power plant components and materials is crucial for the power plant’s safety, and for its upgradation and life extension. The health monitoring of power plant materials, such as steel, is mostly done by employing conventional non-destructive evaluation (NDE) techniques. Considering the limitations associated with conventional NDE techniques, thermoelectric power based NDE (TNDE) is being explored. This paper presents the first ever development and successful demonstration of TNDE in Pakistan. Moreover, the aging analysis of carbon steel grade SA 106B is also being presented for the first time. The extraction-steam pipe samples (new and aged) of SA 106B, from a 46-years-old operating nuclear power plant, are being analyzed and the sensitivity of TNDE to aging induced changes in microstructure is demonstrated. Further, the aged SA 106B is simulated via heat treatment and the equipment is calibrated for its utilization in the nuclear power plant. The correlation between thermoelectric power (TEP) and Vicker hardness (HV) [TEP (µV/oC) = ~2x10-5 Hardness (HV) + 0.008] has been analyzed. It is revealed that the technique has the potential to analyze mechanical properties of aged extraction steam piping without cutting and taking the samples to the laboratory.

How can a diverse set of integral and semi-integral measurements inform identification of discrepant nuclear data?

Nuclear data are used for a variety of applications, including criticality safety, reactor performance, and material safeguards. Despite the breadth of use-cases, the effective neutron multiplication factor, keff, of ICSBEP critical assemblies are primarily used for nuclear data validation; these are sensitive to specific energy regions and nuclides and are unable to uniquely constrain nuclear data. As a consequence, general-purpose nuclear data libraries, such as ENDF/B-VIII.0 [1], may have deficiencies that, while not apparent in criticality applications, negatively impact other applications, such as non-destructive analysis of special nuclear material [2, 3] and neutron diagnosed subcritical experiments [4]. Recent work by the Experiments Underpinned by Computational Learning for Improvements in Nuclear Data (EUCLID) project developed a machine learning tool, RAFIEKI, which uses random forests and the SHAP metric to determine which nuclear data contribute most to predicted bias between measured and simulated responses (e.g. keff). This paper contrasts RAFIEKI analysis applied to keff only against RAFIEKI analysis with keff paired with either LLNL pulsed sphere measurements or subcritical benchmarks. Two examples show that a) including pulsed sphere measurements substantially increases 9Be nuclear data importance to bias between 2 and 15 MeV, and b) including subcritical benchmarks has the potential for disentangling compensating errors between 240Pu (n,el) and (n,il) cross-sections between 0.1 and 10 MeV. These results show that RAFIEKI analysis applied to response sets that include, but go beyond, keff can aid nuclear data evaluators in identifying issues in nuclear data.

Simulating Araponga - The High-Resolution Diffractometer of Brazilian Multipurpose Reactor

The Brazilian Multipurpose Reactor (RMB) is a fundamental project that aims to turn Brazil into a self-sufficient country in the production of radioisotopes and radiopharmaceuticals to supply the Unified Health System (SUS) as much as the private institutions. In addition, the RMB project describes other applications as irradiation and testing of nuclear fuels and structural material analysis, for instance. There are many techniques in the project to study structural aspects of materials, where neutron diffraction represents one of the priorities for implementation. This technique will take place mainly on two diffractometers on Thermal Neutron Guide 1 (TG1), namely Araponga, a high-resolution diffractometer, and Flautim, a high-intensity diffractometer. In this work, we study the performance of the Araponga diffractometer through McStas simulations with input produced by the MCNP code of the RMB core. We investigate the neutron flux values considering a state-of-art high-resolution diffractometer, and the results are promising since some simulated scenarios present values compatible with high-intensity devices.

Critical comparison of INAA and ICP-MS applied in the characterization of purity of TRISO fuel and substrates to its production

Abstract The application of inductively coupled plasma mass spectrometry (ICP-MS), both in solution and laser ablation (LA) mode, and instrumental neutron activation analysis (INAA) in the nuclear material analysis are presented in this paper. The possibility of each technique for the chemical characterization of substances used during TRISO fuel production and its advantages and limitations are discussed based on the obtained results of the analysis of real materials used in TRISO fuel production in the Institute of Nuclear Chemistry and Technology. The paper also reports the application of INAA and LA-ICP-MS to the verification of the purity of the protective layers of pyrolytic carbon (PyC) and silicon carbide.

Safe and Quantitative Analysis of Nuclear Materials From the Milli to Nano-Scale

Safe and Quantitative Analysis of Nuclear Materials From the Milli to Nano-Scale

Overview of ion chromatographic applications for the analysis of nuclear materials: Case studies

AbstractAccurate, precise, and rapid analytical monitoring of various nuclear materials is essential for the smooth functioning of nuclear reactors. Ion chromatography (IC) has emerged as an effective analytical tool for simultaneous detection of different ions in a wide range of materials used in the nuclear industry. The major advantages over other techniques include superior selectivity and sensitivity for detection of anions and cations, wide dynamic range, and speciation studies of ions. This article provides an overview of different ion chromatographic methodologies developed for the analyses of various nuclear materials such as fuel, control rods, moderator, coolant, and process streams. Comparison of various analytical aspects of IC over the other routine techniques reveals the ease and multidimensional capability of the technique. An insight is given to the modern variations in the field such as coupling of IC with other techniques for the characterization of nuclear matrices, implementation of capillary IC in terms of miniaturization, and so on. The information presented herein will serve as a very useful resource for investigators in the field of characterization of nuclear materials.

Monte Carlo simulation for the analysis of various solid samples using handheld X-ray fluorescence spectrometer and evaluation of the effect by environmental interferences

Handheld X-ray fluorescence (HH-XRF) has expanded its utilization areas according to recent technological developments. Most current applications, though, are still concentrated in traditional areas including mineral resource analysis and environmental regulation rather than forensic science for the purpose of investigating a nuclear security event involving nuclear material out of regulatory control. To apply HH-XRF to nuclear material analysis, it is necessary to first obtain calibration data using standard reference materials. Considering the difficulty in obtaining such standard reference materials as well as the high costs involved, one well-known alternative method is to use Monte Carlo simulation code. This study investigated the feasibility of employing Monte Carlo N-Particle transport 6 (MCNP6) simulation to provide calibration data through comparison with experimental measurements of pure solid samples of graphite, copper, SiO2, and UO2 using HH-XRF. The results showed that the MCNP6 simulation results were entirely consistent with the measurement spectra, except for environmental interferences stemming from interactions with the mechanical components below 10 keV which varied slightly according to sample type. To quantitatively evaluate the effect of these environmental interferences on the whole spectrum, the coefficient of determination (R2) was used. In the case of graphite, the effect of the environmental interferences was evaluated to be about 20% on the conformity of the measured and simulated results, while those for copper, SiO2, and UO2 were about 1%, 3%, and less than 1%, respectively. These results indicate that samples having elements with higher rates of photoelectric absorption followed by fluorescence compared to scattering tend to decrease the effect of the environmental interferences over the entire spectrum. The origin of the environmental interferences was estimated to be interference with the detector shield and/or X-ray tube collimator, which are particular design features of the device used. Their effect on contributing to the environmental interferences was evaluated by experiment for the detector shield and simulation for the X-ray tube collimator. As the detector shield was found to only contribute to a decrease in overall spectrum intensity, the major contributor to the environmental interferences was determined to be the collimator. It is believed that the results of this study will help to confirm that Monte Carlo simulation can properly provide calibration data for using HH-XRF on nuclear materials for which reference materials are hard to obtain.

Hydrogen isotopic analysis of nuclear reactor materials using ultrafast laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy is a promising method for rapidly measuring hydrogen and its isotopes, critical to a wide range of disciplines (e.g. nuclear energy, hydrogen storage). However, line broadening can hinder the ability to detect finely spaced isotopic shifts. Here, the effects of varying plasma generation conditions (nanosecond versus femtosecond laser ablation) and ambient environments (argon versus helium gas) on spectral features generated from Zircaloy-4 targets with varying hydrogen isotopic compositions were studied. Time-resolved 2D spectral imaging was employed to detail the spatial distribution of species throughout plasma evolution. Results highlight that hydrogen and deuterium isotopic shifts can be measured with minimal spectral broadening in a ∼ 10 Torr helium gas environment using ultrafast laser-produced plasmas.

Radioactivity and Risk Assessment with Uncertainty Treatment for Analysis of Black Sand Minerals

Precise radiological analysis of environmental, ores, nuclear materials and minerals samples is of great value for monitoring and surveillance objectives. The information deduced from the analysis can be used to identify the origin and nature of the accompanied activities. This work focuses on analysis of some black sand ore samples to identify and quantify their radioisotopes and potential risk. The analysis can provide useful information about the environmental transport mechanism and about the sources of radionuclides in the studied area; Rashid city coast, Egypt. To achieve this target, a Non‐destructive gamma spectrometer (NDGS) was used to trace and amount the radioisotopes types and activities. The efficiency was calculated with uncertainty treatment. The specific activity with uncertainty assessment of 238U, 232Th decay series and 40K of these samples were varied from 72.2 to 252.4 with average value 111 ± 25 Bq·kg–1, 94.2 to 579.8 with average value 140 ± 22 Bq·kg–1 and 427.9 to 527.5 with average value 475 ± 36 Bq·kg–1 respectively. The mineralogical signature of the analyzed samples (XRD) indicates that the samples are mainly composed of ilmenite, zircon, rutile, sphene and monazite. The potential risk assay shows that the hazard parameters of these samples; the Absorbed Gamma Dose Rate (AGDR), Gamma Activity Index (Iγ), Annual Effective Dose Rate Equivalent (AEDRE), Radium equivalent, External and Internal Hazard Index (Hex and Hin) are of specific characteristics. The total absorbed gamma dose rate and the annual effective dose due these samples were found to be with average values 158 ± 24 (nGy/h) and 195 ± 29 (μSv/y) which are higher than the world average value of 59 nGy/h and 70 μSv/y respectively. The results obtained are important to establish baseline levels to detect any upcoming changes due to any activities. It can be observed that the studied area has elevated thorium and uranium content. The relatively high dose rate will be considered as a spa for the physical therapy such as treatment of some skin diseases and rheumatoid.

In situ liquid SIMS analysis of uranium oxide

Trace analysis of nuclear materials in solid particles collected in the environment or particles in liquid slurry generated in nuclear material manufacturing processes can pinpoint elemental, organic, and isotopic signatures of nuclear fuel cycle activities and processes. Such information can support nuclear safeguards programs by increasing our ability to detect undeclared nuclear materials, routine activities for safeguarding at declared facilities, and illicit activities. However, trace radioactive material analysis in liquids and slurries is challenging using bulk approaches. For example, one drawback of sensitive analysis such as inductively coupled plasma mass spectrometry (ICP‐MS) is that sample is consumed or destroyed as a result of the technical approach. We developed a vacuum compatible microfluidic interface to enable surface analysis of liquids and solid–liquid interactions using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). In this work, we illustrate the initial results from the analysis of liquid uranium oxide standard solutions using in situ liquid SIMS. Because the liquid SIMS analysis is almost nondestructive, the same sample can then be analyzed by other analytical techniques or saved for future reference. Consequently, multimodal analysis is possible. Our results demonstrate that in situ liquid SIMS can be used as a new approach to analyze radioactive materials in liquid and slurry forms of relevance to diverse applications.