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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

MIS High-Purity Plutonium Oxide Metal Oxidation Product BLO-39-11-14-004 (SSR132 and 132A): Final Report

A high-purity, reactor-grade plutonium dioxide material from the Material Identification and Surveillance (MIS) Program inventory has been studied with regard to gas generation and corrosion in a storage environment. BLO-39-11-14-004 is a high specific power oxide that represents Hanford process plutonium oxides from oxalate process product, oxalate precipitation of impure plutonium and pure mixed uranium/plutonium nitrate solutions, PFP NDA and impure and scrap plutonium oxides 80-85% from PFP and the 300 area. It also represents plutonium oxides from oxalate precipitation at LANL and Savannah River. After calcination to 950 °C, the material contained 80% plutonium and 7% americium with no major impurities. This study followed over time the gas pressure of a sample with nominally 0.5 wt% water in a sealed container with an internal volume scaled to 1/500th of the volume of a 3013 container. A leak occurred in the original reactor (SSR132) which was terminated after 3 years. The sample was reloaded (SSR132A) and an additional set of data was collected. Results from both loadings are discussed. Gas compositions were measured periodically over three (SSR132) and four and a half (SSR132A) year periods. The maximum observed gas pressures were 93 kPa and 94 kPa, respectively. The increase over the initial pressure was primarily due to generation of nitrogen gas. For SSR132, the maximum observed gas pressure for hydrogen was 1.2 kPa and oxygen was 9.3 kPa (includes oxygen from leak). For SSR132A, the maximum observed gas pressure for hydrogen was 5.5 kPa and oxygen was 0.9 kPa. At the completion of the study, the internal components of the sealed container showed limited signs of corrosion.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Application of a Density Law via Python for Aqueous Plutonium Nitrate

A predictive density tool has been developed in Python to reduce bias and uncertainty in nuclear criticality safety calculations for plutonium nitrate systems. The Pitzer Method and an empirical method were implemented into the tool, allowing for plutonium nitrate density calculations. Additionally, the Python tool can generate atom densities for a MCNP6.2 material card using the density from the selected method and directly the densities into a prepared MCNP6 input text file. The material card and density are calculated based on customizable user inputs of plutonium content, nitric acid content, temperature, plutonium isotope weight percentages and impurity concentrations. The Python tool has been validated and verified against the International Handbook of Evaluated Criticality Safety Benchmark Experiments to predict densities within a root mean square error of 1.0% for the Pitzer method and 1.8% for the empirical method. These errors in density were shown to lead to a ±0.5% error in MCNP6.2 calculated k effective for the Pitzer method and a ±1.7% error for the Empirical method. Simultaneous work is also being done at the University of New Mexico and Los Alamos National Laboratory to create a similar tool for plutonium chloride solutions, which aims to provide the accreditation of the chlorine absorption. These capabilities will not only provide more accurate models but also lead the way towards a better understanding of solution systems and potential relaxation in the conservatism of the current aqueous plutonium processing limits.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2013

Controllability of plutonium concentration for FBR fuel at a solvent extraction process in the PUREX process

Typical Purex solvent extraction systems for the reprocessing of spent nuclear fuel have a feed material containing dilute, 1% in weight, plutonium, along with uranium and fission products. Current reprocessing proposals call for no separation of the pure plutonium. The work described in this paper studied, by computer simulation, the fundamental feasibility of preparing a 20% concentrated plutonium product solution from the 1% feed by adjusting only the feed rates and acid concentrations of the incoming streams and without the addition of redox reagents for the plutonium. A set of process design flowsheets has been developed to realize a concentrated plutonium solution of a 20% stream from the dilute plutonium feed without using redox reagents. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Using Biomolecules to Separate Plutonium - 18393

Relying on the thermodynamics and the reaction kinetics of the metal-ligand bond is the traditional approach to selective separation of metals such as plutonium. An alternative is to use a biologically based separation that leverages multiple factors to sense, bind and transport metals in a series of steps. The protein serum transferrin (Tf) handles the regulation and transport of iron in the blood. Iron and a synergistic anion bind to Tf in one or both of Tf's two lobes (N-lobe and C-lobe). The conformation of Tf changes due to the lobes closing around the metals. The conformational change that occurs when a metal ion and synergistic anion bind to transferrin can trigger additional interactions with the transferrin receptor protein and the subsequent transport of the metal-transferrin complex into cells. Transferrin also is known to bind and transport plutonium into cells but this process is less efficient than iron transport because certain plutonium-transferrin complexes appear to be unable to trigger the same conformational change in transferrin as the iron-transferrin complex. We hypothesize that the synergistic anion is the cause of the different conformational changes that inhibit plutonium-transferrins from binding to the transferrin receptor protein. Using cerium as a non-radioactive surrogate for plutonium(IV), we have been able to synthesize cerium-transferrin complexes with only carbonate as the synergistic anion as a prelude to experiments with plutonium-transferrin complexes that can test our hypothesis. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Subcritical Copper-Reflected-α-phase Plutonium (SCRαP) Integral Experiment Design

A Subcritical Copper-Reflected α-phase Plutonium (SCRαP) integral benchmark experiment is proposed where multiplication will be approximated using correlated neutron data from a detector system consisting of {sup 3}He tubes inside polyethylene. Measurements will be performed on various subcritical experimental configurations consisting of a weapons-grade plutonium sphere surrounded by different Cu thicknesses. In addition to the proposed base experimental configurations with Cu, additional configurations are planned with the plutonium ball nested in various thicknesses of interleaved polyethylene spherical shells mixed in with the Cu shells. The polyethylene is intended to provide fast neutron moderation and reflection, resulting in additional measurements with differing multiplication, spectra, and nuclear data sensitivity. The proposed experiments will performed at the National Criticality Experiments Research Center (NCERC). NCERC is home to a 4.5-kg α-phase stainless steel clad plutonium sphere that is referred to as the BeRP (Beryllium-Reflected Plutonium) ball due to its historical use in a beryllium-reflected critical experiment. In 2014, similar subcritical measurements were performed with the BeRP ball surrounded by nickel and tungsten. The nickel-reflected measurements were documented as a benchmark evaluation which was accepted by the International Criticality Safety Benchmark Evaluation Project (ICSBEP). Similar to past measurements, the proposed work will help both identify deficiencies and quantify uncertainties in nuclear data and validate computational methods related to neutron multiplication inference for subcritical benchmark evaluations. Monte Carlo simulations were performed for the preliminary design of a subcritical Copper-Reflected - phase Plutonium (SCRP) integral benchmark experiment. Specifically, MCNP{sup R} version 6 was used to determine the k{sub eff} and associated nuclear data sensitivities for different preliminary configurations (reflector thickness, material type). The final experimental design process will include continuous-energy nuclear data sensitivity analysis. This will help assess the potential impact of this integral measurement as it relates to international efforts to continuously improve current libraries (ENDF, JEFF, JENDL etc) that still tend to over/under-estimate the measured results of integral experiments, sometimes significantly. Deficiencies in underlying nuclear data quantities such as Nubar have been shown to have an effect on inferred values from subcritical measurements as well. The proposed experiments and subsequent computational validation will help identify such deficiencies. It will also help validate new nuclear data evaluations, including one for Cu that was recently performed in the resolved region up to 100 MeV for {sup 65}Cu and {sup 63}Cu which is expected to improve Cu-related benchmark simulation performance. The final experimental design phase will also include simulation results that will incorporate the detectors that will be used for the subcritical measurements. For the benchmark portion of the measurements, the main detectors that are being considered are portable neutron multiplicity counters made up of {sup 3}He tubes embedded in polyethylene and lined with cadmium. These detectors employ a data acquisition system that produces list-mode data (correlated information where each event is listed sequentially) that can be analyzed using the Feynman variance-to-mean method. Other detector systems including SNAP (single {sup 3}He tube embedded in polyethylene), and a high-purity germanium (HPGe) detector are being considered for supplementary measurements only and are not intended to be used for the final benchmark measurements. Decoupling the supplementary detectors from the system eliminates any contribution to the total system multiplication, and greatly simplifies the final computational benchmark model. Therefore, an optimization of the portable neutron multiplicity counter placement in the benchmark measurements will be performed to ensure that there is minimal contribution to the total system multiplication. In addition, new temperature measurement techniques and hardware will be explored. (authors)

42 ENGINEERING↗
DOE OSTI2019

Extension of the Plutonium Oxide Nanocluster Family to Include {Pu 16 } and {Pu 22 }

Plutonium(IV) oxide nanoclusters represent an interesting scientific problem regarding structure-function relationships and are also relevant to global concerns surrounding plutonium reprocessing, the remediation of plutonium-contaminated soils, and the storage or disposal of plutonium-containing wastes. Here we report the synthesis of five unique Pu IV oxide nanoclusters containing 38,22, or 16 metal centers and capped only with inorganic ligands, such as chlorine and water, which prevent formation of the extended PuO 2 structure. The products are interrogated through single-crystal X-ray diffraction, bond valence calculations, and comparisons to other known metal-oxide nanoclusters. Of particular interest is the in-corporation of hydroxide linkages into the smaller plutonium oxide nanoclusters, which underscores previous observations and hypotheses regarding the formation of plutonium polymers and colloids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Raman and infrared spectra of plutonium (IV) oxalate and its thermal degradation products

For over 80 years, plutonium dioxide has been routinely produced via thermal decomposition of hydrated plutonium(IV) oxalate. Despite the longstanding utility of this process, the chemical structures of starting materials and intermediates produced during this thermal conversion remain ill-defined. To help resolve this uncertainty, we measured high-resolution Raman and infrared spectra of Pu(C 2 O 4 ) 2 ·6H 2 O that was heated to 25, 100, 220, 250, 350, and 450 °C in air. Our measurements show that Pu(C 2 O 4 ) 2 ·6H 2 O has a rich vibrational spectrum with at least 15 Raman bands between 180 cm -1 and 1900 cm -1 and 9 infrared bands between 800 cm -1 and 4000 cm -1 . As Pu(C 2 O 4 ) 2 ·6H 2 O is heated, water is liberated, and the oxalate ligand decomposes to produce plutonium oxycarbide species. When heated to 350 °C or higher, vibrational spectra are consistent with PuO 2 with some residual carbon-containing species. Full vibrational spectra, powder X-ray diffraction, and scanning electron microscopy measurements of Pu(C 2 O 4 ) 2 ·6H 2 O and its thermal degradation products are presented herein along with approximate assignments for observed spectral bands. These data can be used to validate and potentially improve existing computational models that describe the chemical structure of compounds produced during thermal degradation of plutonium (IV) oxalate. Given the utility of plutonium (IV) oxalate in synthesizing plutonium dioxide, these results are expected to provide value in the fields of nuclear fuel processing, nuclear nonproliferation, and nuclear forensics.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Verification of Plutonium Content in PuBe Sources Using MCNP® 6.2.0 Beta with TENDL 2012 Libraries

Although the production of PuBe neutron sources has discontinued, hundreds of sources with unknown or inaccurately declared plutonium content are in existence around the world. Institutions have undertaken the task of assaying these sources, measuring, and calculating the isotopic composition, plutonium content, and neutron yield. The nominal plutonium content, based off the neutron yield per gram of pure 239 Pu, has shown to be highly inaccurate. New methods of measuring the plutonium content allow a more accurate estimate of the true Pu content, but these measurements need verification. Using the TENDL 2012 nuclear data libraries, MCNP6 has the capability to simulate the (α, n) interactions in a PuBe source. Theoretically, if the source is modeled according to the plutonium content, isotopic composition, and other source characteristics, the calculated neutron yield in MCNP can be compared to the experimental yield, offering an indication of the accuracy of the declared plutonium content. In this study, three sets of PuBe sources from various backgrounds were modeled in MCNP6 1.2 Beta, according to the source specifications dictated by the individuals who assayed the source. Verification of the source parameters with MCNP6 also serves as a means to test the alpha transport capabilities of MCNP6 1.2 Beta with TENDL 2012 alpha transport libraries. Finally, good agreement in the comparison would indicate the accuracy of the source parameters in addition to demonstrating MCNP's capabilities in simulating (α, n) interactions.

(α,n)↗
DOE OSTI2015

Plutonium Isotopes in the Terrestrial Environment at the Savannah River Site, USA. A Long-Term Study

This work presents the findings of a long term plutonium study at Savannah River Site (SRS) conducted between 2003 and 2013. Terrestrial environmental samples were obtained at Savannah River National Laboratory (SRNL) in A-area. Plutonium content and isotopic abundances were measured over this time period by alpha spectrometry and three stage thermal ionization mass spectrometry (3STIMS). Here we detail the complete sample collection, radiochemical separation, and measurement procedure specifically targeted to trace plutonium in bulk environmental samples. Total plutonium activities were determined to be not significantly above atmospheric global fallout. However, the 238 Pu/ 239+240 Pu activity ratios attributed to SRS are above atmospheric global fallout ranges. The 240 Pu/ 239 Pu atom ratios are reasonably consistent from year to year and are lower than fallout, while the 242 Pu/ 239 Pu atom ratios are higher than fallout values. Overall, the plutonium signatures obtained in this study reflect a mixture of weapons-grade, higher burn-up, and fallout material. This study provides a blue print for long term low level monitoring of plutonium in the environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Rapid quantitative analysis of trace elements in plutonium alloys using a handheld laser-induced breakdown spectroscopy (LIBS) device coupled with chemometrics and machine learning

Here, we present the first reported quantification of trace elements in plutonium via a portable laser-induced breakdown spectroscopy (LIBS) device and demonstrate the use of chemometric analysis to enhance the handheld device's sensitivity and precision. Quantification of trace elements such as iron and nickel in plutonium metal via LIBS is a challenging problem due to the complex nature of the plutonium optical emission spectra. While rapid analysis of plutonium alloys has been demonstrated using portable LIBS devices, such as the SciAps Z300, their detection limits for trace elements are severely constrained by their achievable pulse power and length, light collection optics, and detectors. In this paper, analytical methods are evaluated as a means to circumvent the detection constraints. Three chemometric methods often used in analytical spectroscopy are evaluated; principal component regression, partial least-squares regression, and artificial neural networks. These models are evaluated based on goodness-of-fit metrics, root mean-squared error, and their achievable limits of detection (LoDs). Partial least squares proved superior for determining content of iron and nickel in plutonium metal, yielding LoDs of 15 and 20 ppm, respectively. These results of identifying the undesirable trace elements in plutonium components are critical for applications such as fabricating radioisotope thermoelectric generators or nuclear fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Nuclear Archaeology to Distinguish Plutonium and Tritium Production Modes in Heavy-Water Reactors

Several nuclear archaeology techniques have been proposed to determine historic plutonium production in dedicated nuclear reactors. These methods rely on sampling materials from the reactor core or specially designed monitor tags, to examine suited isotopic ratios and deduce the amount of plutonium produced. However, some production reactors can be used to produce other isotopes than plutonium, such as tritium. If a reactor has been declared to produce tritium, it could be crucial to confirm that this was the case and that the reactor was not used to produce plutonium instead. In this paper, we describe how isotopic ratios discrepancies can be used to distinguish between plutonium and tritium production modes. Here, we present results obtained via the simulation of reactor lattices inspired by Savannah River Site heavy water production reactors and show that elements such as hafnium and tungsten can be conveniently used to detect undeclared production of plutonium.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

URINARY EXCRETION OF PLUTONIUM IN MAYAK WORKERS DURING AND AFTER CA-DTPA ADMINISTRATION

Chelation therapy is sometimes used after potential exposures to plutonium to increase urinary excretion of the radionuclide to improve the accuracy of bioassay measurements. The purpose of this report is to describe the enhancement of urinary excretion of plutonium during and after the administration of the trisodium salt of calcium diethylenetriaminepentaacetate (Ca-DTPA) daily for 3 d to a group of male and female plutonium workers from the Mayak Production Association in Ozyorsk, Russia. One-hundred and two cases (18 females and 84 males) were selected where urinary contents of plutonium, prior to chelation, exceeded the detection threshold. Daily urine collections were obtained during the 3 d of Ca-DTPA treatments. In addition, 58 of these cases had urine bioassays at 1–45 d after chelation. The daily enhancement over baseline values excretion of plutonium was found to be 50.4×/1.4 (geometric mean and geometric standard deviation); 58.9×/1.2; 72.9×/1.4 in the first, second and third days of Ca-DTPA administration. The mean enhancement for the 3-d period was 60.1×/1.7. The rate of plutonium excretion from 1 to 45 d after chelation decreased with a half-period of 3.9 d and the chelation enhancement factor (Кenh-i) is described by the function Кenh-i = (0.79 ± 0.24) + (42.9 ± 1.2) × e-(0.18 ± 0.01) × day.

Environmental Sciences & Ecology↗
DOE OSTI2023

Chelation Model Validation: Modeling of a Plutonium-238 Inhalation Incident Treated with DTPA at Los Alamos National Laboratory

Accidental inhalation of plutonium at the workplace is a non-negligible risk, even when rigorous safety standards are in place. The intake and retention of plutonium in the human body may be a source of concern. Thus, if there is a suspicion of a significant intake of plutonium, medical countermeasures such as chelation treatment may be administered to the worker. The present work aimed to interpret the bioassay data of a worker involved in an inhalation incident due to a glovebox breach at Los Alamos National Laboratory’s plutonium facility. The worker was treated with intravenous injections of calcium salts of diethylenetriaminepentaacetic acid (DTPA) in an attempt to reduce the amount of plutonium from the body and therefore reduce the internal radiation dose. It is well known in the internal dosimetry field that the administration of chelation treatment poses additional challenges to the dose assessment. Hence, a recently developed chelation model was used for the modeling of the bioassay data. The objectives of this work are to describe the incident, model the chelation-affected and non-affected bioassay data, estimate the plutonium intake, and assess the internal radiation dose.

238Pu↗
DOE OSTI2021

TA-55 Plutonium Facility Fact Sheet

At the Los Alamos National Laboratory (LANL), virtually all plutonium operations occur within the Plutonium Facility at Technical Area 55 (TA-55). TA-55 is the nation’s most modern plutonium science and manufacturing facility, and is the only fully operational, full capability plutonium facility in the nation. TA-55 supports a wide range of national security programs that involve: 1) stockpile stewardship. 2) plutonium processing. 3) nuclear materials stabilization. 4) materials disposition. 5) nuclear forensics. 6) nuclear counter-terrorism. 7) nuclear energy. Operations at TA-55 maintain a critical skill base of plutonium expertise across a broad suite of technical capabilities. These capabilities form a center of excellence for actinide science and technology, including world-class manufacturing for solving significant national security challenges.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Discrete-event Simulation Process Model for the Pyrochemical Processing of Plutonium at Los Alamos National Laboratory

The pyrochemical metal production operations that occur in the Plutonium Facility at Los Alamos National Laboratory perform plutonium purification with the aim to provide plutonium metal for a variety of defense- and non-defense missions within the National Nuclear Security Administration. The demands and constraints associated with the pyrochemical processing of plutonium are complex, making decision analyses challenging for program managers who require plutonium production for their mission applications. The construction of a discrete-event simulation process model is proposed to measure and report the process capacity, material throughput, equipment requirements, and dose accumulation for operators of the pyrochemical metal production operations. The process model, constructed in the ExtendSim™ software, will represent the cause-and-effect relationships between the pyrochemical processing environment and the process constraints, including criticality limitations, material control and accountability measures, chemical analysis requirements, and equipment availability. An accurate representation of the pyrochemical metal production process capacity through simulation modeling will be helpful to program managers in their efforts to forecast plutonium availability for mission applications. Furthermore, the proposed process model will be vital for future analyses that will measure the interactions between the pyrochemical metal production operations and the aqueous reprocessing operations and their ability to minimize transuranic waste disposal.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Data Mining of the Rocky Flats Library Archive for Plutonium Compatibility Studies

The objective of this project was to create a searchable database of plutonium compatibility studies from the Rocky Flats Archive. The Rocky Flats Plant was a manufacturing complex in Golden, Colorado that produced nuclear weapons. It primarily focused on producing plutonium pits, which were the cores of many nuclear implosion-type weapons. Because plutonium is an extremely reactive metal, avoiding the use of incompatible materials is imperative to avoid damaging the plutonium pit during its production. The Rocky Flats Plant had conducted extensive surveys of materials used in plutonium pit fabrication for their compatibility with plutonium.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Cleaning up the Legacy of the Cold War: Plutonium Oxides and the Role of Synchrotron Radiation Research

The deceptively simple binary formula of AnO 2 belies an incredibly complex structural nature, and propensity to form mixed-valent, nonstoichiometric phases of composition AnO 2±x . For plutonium, the very formation of PuO 2+x has challenged a long-established dogma, and raised fundamental questions for long-term storage and environmental migration. This presentation covers two aspects of Los Alamos synchrotron radiation studies of plutonium oxides: (1) the structural chemistry of laboratory-prepared AnO 2+x systems (An = U, Pu; 0 ≤ x ≤ 0.25) determined through a combination of x-ray absorption fine structure spectroscopy (XAFS) and x-ray scattering of laboratory prepared samples; and (2) the application of synchrotron radiation towards the decontamination and decommissioning of the Rocky Flats Environmental Technology Site. Making the case for particle transport mechanisms as the basis of plutonium and americium mobility, rather than aqueous sorption-desorption processes, established a successful scientific basis for the dominance of physical transport processes by wind and water. The scientific basis was successful because it was in agreement with general theory on insolubility of PuO 2 in oxidation state IV, results of ultrafiltration analyses of field water/sediment samples, XAFS analyses of soil, sediment, and concrete samples, and was also in general agreement with on-site monitoring data. This understanding allowed Site contractors to rapidly move to application of soil erosion and sediment transport models as the means of predicting plutonium and americium transport, which led to design and application of site-wide soil erosion control technology to help control downstream concentrations of plutonium and americium in streamflow.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Storage and concentration of plutonium and uranium solutions in LES 401 hot cell (ATALANTE) - criticality safety considerations - 14414

ATALANTE, located in Marcoule, is one of the main nuclear facilities of the French CEA (Atomic Energy and Alternative Energies Commission). The LES 401 hot cell was built in the 1980's and, since then, has been operating only with low masses of fissile material. As part of the management optimization for purified Uranium and Plutonium solutions ('Fin U Pu' Project), the new functions provided in LES 401 are now expected to be the following: - Reception of Uranium and Plutonium solutions, - Concentration of these solutions, - Storage of the concentrates and distillates. From the criticality safety point of view, the equipment was originally designed in safe geometry for Plutonium Nitrate, considering only a 2.5 cm -thick water reflector. However, the new criticality safety case had to take into account the following points: - Reception of not only Plutonium solutions, but also highly enriched Uranium solutions, - Considering flood risk as a possible contingency, - Considering precipitation as a possible contingency. These more conservative assumptions have meant introducing a mass limit for the cell, in addition to the geometry control mode. For the equipment containing very low concentrations of fissile material in normal operation, it was necessary, using the double contingency principle, to take a concentration limit into account in the specific situation of water flooding the cell. Finally, given the mass and geometry control mode, it was necessary to perform all the calculations with both fissile media (Plutonium and Uranium), as it was found that depending on the selected mass, geometry, and reflection conditions, the most penalizing media is not always the same. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗