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

Americium Utilization Via Pyroelectrochemical Granulation and Vibrocompaction Technologies

An experiment in which americium is introduced into the composition of fuel pins with vibrocompacted uranium-plutonium oxide fuel is described within the scope of work performed on the development of a closed fuel cycle for a fast reactors. Possible directions of R&D work for validating the design, fabrication technology, and serviceability of fuel pins with fuel containing americium are examined. A variant based on the chemical-technological complex at the Research Institute for Atomic Reactors (NIIAR) is proposed for developing centralized production of americium burn-out elements for liquid-metal cooled fast reactors. The assimilated remote-controlled technologies of pyroelectrochemical granulation of oxide fuel compositions and vibrocompaction in radiation protected boxes as well as the automated equipment specially developed within the special federal program are proposed for manufacturing the burn-out elements.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Utilization of non-weapons-grade plutonium and highly enriched uranium with breeding of the {sup 233}U isotope in the VVER reactors using thorium and heavy water

A method for joint utilization of non-weapons-grade plutonium and highly enriched uranium in the thorium–uranium—plutonium oxide fuel of a water-moderated reactor with a varying water composition (D{sub 2}O, H{sub 2}O) is proposed. The method is characterized by efficient breeding of the {sup 233}U isotope and safe reactor operation and is comparatively simple to implement.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Towards application of a neutron cross-section uncertainty propagation capability in the criticality safety methodology - 14434

At the Paul Scherrer Institute (PSI) the methodology for criticality safety evaluations (CSE) used for Swiss applications is focused, following common practice, on establishing an upper subcriticality limit (USL) for the effective neutron multiplication factor (k{sub eff}), based on a statistical evaluation of the obtained validation results in terms of the calculated-to-benchmark k{sub eff} values. Recently, a new computational tool referred to as NUSS (Nuclear data Uncertainty Stochastic Sampling) was developed in order to propagate neutron-nuclear data (ND) uncertainties in calculations with Monte Carlo transport codes in combination with general-purpose ND libraries in ACE format. Thereby, this tool should now allow for a quantification of ND data uncertainties in CSE and to introduce these into the CSE criteria definition. This paper concerns an application of the NUSS methodology for criticality validation studies. Calculated k{sub eff} uncertainty estimations were obtained for the current PSI validation suite including in total 149 critical benchmark configurations for which in-house MCNP(X) models were developed, covering both uranium and mixed uranium-plutonium oxide fuels. The MCNPX-2.7.0 code was used together with the ENDF/B-VII.1 ND library while the ND variance-covariance matrixes (VCM) were taken from both SCALE-6.0 44-group libraries and also from ENDF/B-VII.1 files. Based on the newly obtained information on the uncertainties, a re-assessment of the lower tolerance bound (LTB) for k{sub eff} using the total uncertainties as weighting factors is proposed as means for the present PSI CSE methodology upgrade and some possible directions of further methodology enhancements are discussed next. (authors)

42 ENGINEERING↗
DOE OSTI2021

Rapid dissolution of PuO 2 analytical samples using mediated electrochemical oxidation

Current methods for quantitative dissolution of solid PuO 2 involve lengthy dissolution times. The adaptation of mediated electrochemical oxidation, which uses an electrochemically produced oxidizing agent to catalyze dissolution, has been explored for radiochemical analysis scale dissolutions of PuO 2 . The effects of temperature, electrode material, and electrocatalyst on the dissolution kinetics were explored. Under conditions examined in this study, complete dissolution of tens of milligrams of solid PuO 2 can be achieved in less than 1 h at ambient temperature. Overall, this methodology could be adapted to dissolve other metal oxides.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

A Rapid Sequential Separation Method for Determination of Actinides and TENORM in Fracking Wastes - 20223

With recent advances in unconventional drilling technology in the US and around the world, the risks of environmental contamination and exposure due to technologically enhanced naturally occurring radioactive materials (TENORM) from fracking wastes have also surfaced. Although the Permian Basin (southeastern New Mexico, western Texas) has long been a modest producer of oil, the advent of fracking technology a decade ago turned it into hot property for producers. A 2018 assessment of undiscovered, technically recoverable continuous oil and gas resources by the U.S. Geological Survey estimates an average 46.3 billion barrels of oil and 281 trillion cubic feet of gas. This is likely to increase the use of unconventional drilling and TENORM generation. TENORM concentrations in oil and gas exploration and production waste can be several hundred to several thousand times higher than background TENORM concentrations. Both the thorium and uranium decay chains contribute to airborne radionuclides arising from the radon gas escaping the ground and subsequently decaying as airborne particulates. Additionally, radon decay products {sup 210}Pb and {sup 210}Po can build up in scale on the internal surfaces of oil and gas handling pipes and in sludge in refineries, becoming potential inhalation and ingestion hazards for workers. Furthermore, southeastern NM is also home to world's only licensed and operating transuranic nuclear waste repository, the DoE's Waste Isolation Pilot Plant (WIPP). Plutonium isotopes ({sup 239+240}Pu) and {sup 241}Am, are expected to account for more than 99% of the total radioactivity scheduled for disposal in the WIPP repository. Thus, an improved understanding of the environmental fate and transport of TENORM, liberated by unconventional drilling, is essential to assess how best to protect individuals and the environment. In this context, accurate measurement of TENORM and actinides in environmental and biological samples is essential. In this presentation, a new sequential method for the separation and pre-concentration of actinides (Pu, Am, Np) and TENORM (Po, U and Th) derived from oil and gas exploration is proposed. The TEVA method involves a rapid co-precipitation step to remove matrix interferences from the samples, followed by plutonium oxidation state adjustment to Pu (IV) and an incubation period of ∼ 1 hour at 50-60 deg. C to allow the resultant Po (II) to oxidize into Po(IV). The polonium, neptunium, thorium and plutonium are then separated on a TEVA column, while americium and uranium are separated on a TRU column. After separation, the alpha counting source was prepared by micro-precipitation with copper sulfide (CuS) for polonium and neodymium fluoride (NdF{sub 3}) for actinides. The efficiency and reliability of the procedures were tested by analyzing filter, drinking water and frack sand samples. The method is simple, robust and can be performed quickly with excellent removal of interferences, high chemical recovery and very good alpha peak resolution. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2013

Repackaging of High Fissile TRU Waste at the Transuranic Waste Processing Center - 13240

Twenty-six drums of high fissile transuranic (TRU) waste from Oak Ridge National Laboratory (ORNL) operations were declared waste in the mid-1980's and placed in storage with the legacy TRU waste inventory for future treatment and disposal at the Waste Isolation Pilot Plant (WIPP). Repackaging and treatment of the waste at the TRU Waste Packaging Center (TWPC) will require the installation of additional equipment and capabilities to address the hazards for handling and repackaging the waste compared to typical Contact Handled (CH) TRU waste that is processed at the TWPC, including potential hydrogen accumulation in legacy 6M/2R packaging configurations, potential presence of reactive plutonium hydrides, and significant low energy gamma radiation dose rates. All of the waste is anticipated to be repackaged at the TWPC and certified for disposal at WIPP. The waste is currently packaged in multiple layers of containers which presents additional challenges for repackaging activities due to the potential for the accumulation of hydrogen gas in the container headspace in quantities than could exceed the Lower Flammability Limit (LFL). The outer container for each waste package is a stainless steel 0.21 m{sup 3} (55-gal) drum which contains either a 0.04 m{sup 3} or 0.06 m{sup 3} (10-gal or 15-gal) 6M drum. The inner 2R container in each 6M drum is ∼12 cm (5 in) outside diameter x 30-36 cm (12-14 in) long and is considered to be a > 4 liter sealed container relative to TRU waste packaging criteria. Inside the 2R containers are multiple configurations of food pack cans, pipe nipples, and welded capsules. The waste contains significant quantities of high burn-up plutonium oxides and metals with a heavy weight percentage of higher atomic mass isotopes and the subsequent in-growth of significant quantities of americium. Significant low energy gamma radiation is expected to be present due to the americium in-growth. Radiation dose rates on inner containers are estimated to be 1-3 mSv/hr (100-300 mrem/hr) with an unshielded dose rate on the waste itself of over 10 mSv/hr (1 rem/hr). Additional equipment to be installed at the TWPC will include a new perma-con enclosure and a shielded/inert glovebox in the process building to repackage and stabilize the waste. All of the waste will be repackaged into Standard Pipe Overpacks. Most of the waste (21 of the 26 drums) is expected to be repackaged at the food-pack can level (i.e. the food-pack cans will not be opened). Five of the incoming waste containers are expected to be repackaged at the primary waste level. Three of the containers exceed the 200 gram Pu-239 Fissile Gram Equivalent (FGE) limit for the Standard Pipe Overpack. These three containers will be repackaged down to the primary waste level and divided into eight Standard Pipe Overpacks for shipment to WIPP. Two containers must be stabilized to eliminate any reactive plutonium hydrides that may be present. These containers will be opened in the inert, shielded glovebox, and the remaining corroded plutonium metal converted to a stable oxide form by using a 600 deg. C tube furnace with controlled oxygen feed in a helium carrier gas. The stabilized waste will then be packaged into two Standard Pipe Overpacks. Design and build out activities for the additional repackaging capabilities at the TWPC are scheduled to begin in Fiscal Year 2013 with repackaging, stabilization, and certification activities scheduled to begin in Fiscal Year 2014. Following repackaging and stabilization activities, the Standard Pipe Overpacks will be certified for disposal at WIPP utilizing Non-Destructive Examination (NDE) to verify the absence of prohibited items and Non-Destructive Assay (NDA) to verify the isotopic content under the TWPC WIPP certification program implemented by the Central Characterization Project (CCP). (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Cheesecloth Alternatives Testing

Heat source plutonium oxide (HS-PuO 2 ) enriched with 65% or greater plutonium-238, is recovered and purified using an aqueous nitric acid process. Historically, cheesecloth has been employed for small spill clean-up and for routine housekeeping. However, the 2016 Department of Energy (DOE) Operating Experience report, entitled Nitrate Waste Evaluations, stated that the mixing of nitrate wastes with organic absorbents, such as cheesecloth, may render transuranic waste unacceptable for disposal at WIPP in the future. This report explores the feasibility of replacement of cheesecloth with an alternative sorbent wipe that has similar absorption and cleaning abilities and improved acid resistance. Currently, cheesecloth is used for three different functions in HS-PuO 2 operations: spill cleanup; general housekeeping operations such as cleaning glovebox floors and windows, balances, furnaces, etc.; and decontamination of iridium cladded heat sources containing HS-PuO 2 . Alternatives used for spill cleanup must be able to tolerate high neutron doses found in the HS-Pu gloveboxes. They must also be able to withstand exposure to nitric acid concentrations up to 15.8 M without decomposing. Wipes used for general housekeeping must also be durable enough to clean rough surfaces and remain intact when used for scrubbing. Wipes used for clad decontamination do not need to absorb large amounts of liquid but they must be able to withstand neutron exposures, temperatures of up to several hundred degrees Celsius, and exposure to acid solutions followed by mild scrubbing. Finally wipes used for any purpose must resist chemical reactions with nitric acid that could cause issues for waste disposal such as energetic exothermic reactions or flammable gas build-up. The wipes selected for this study were ranked based on their usability (radiation tolerance, absorbency, integrity in nitric acid, and durability) as well as their chemical compatibility with nitric acid as demonstrated using several types of chemical analyses. Wipes were then ranked based on the combination of their usability and chemical compatibility scores.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Nature of Nano-Sized Plutonium Particles in Soils at the Hanford Site

The occurrence of plutonium dioxide (PuO2) either from direct deposition or from the precipitation of plutonium-bearing solutions in contaminated soils and sediments has been well described, particularly for the Hanford site in Washington State. However, past research has suggested that plutonium may exist in environmental samples at the Hanford site in chemical forms in addition to large size PuO2 particles and that these previously unidentified nano-sized particles maybe more reactive and thus more likely to influence the environmental mobility of Pu. Here we present evidence for the formation of nano-sized plutonium iron phosphate hydroxide structurally related to the rhabdophane group nanoparticles in 216-Z9 crib sediments from Hanford using transmission electron microscopy (TEM). The distribution and nature of these nanoparticles varied depending on the adjacent phases present. Fine electron probes were used to obtain electron diffraction and electron energy-loss spectra from specific phase regions of the 216-Z9 cribs specimens from fine-grained plutonium oxide and phosphate phases. Energy-loss spectra were used to evaluate the plutonium N4,5 (4d → 5f ) and iron L2,3 absorption edges. The iron plutonium phosphate formation may depend on the local micro-environment in the sediments, availability of phosphate, and hence the distribution of these minerals may control long-term migration of Pu in the soil. This study also points to the utility of using electron beam methods for determining the identity of actinide phases and their association with other sediment phases.

Cribs, Soil Contamination↗
DOE OSTI2024

Multiscale Modeling of Plutonium Radiation Chemistry in Nitric Acid Solutions. 1. Cobalt-60 Gamma Irradiation of Pu(IV)

We report careful manipulation of the plutonium oxidation states is essential in the study and utilization of its rich redox chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. To this end, we have developed an experimentally evaluated multiscale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.0, 3.0, and 6.0 M). Under these acidic, aqueous solution conditions, cobalt-60 gamma irradiation afforded marginal net conversion of Pu(IV) to Pu(VI), the extent of which was dependent on the concentration of HNO 3 and absorbed gamma dose. Multiscale calculations, which are in excellent agreement with experimental data, indicate that this observation is due to a combination of inherent plutonium disproportionation reactions and several radiation-induced processes, including redox cycling between Pu(IV) and Pu(III), as achieved by the reduction of Pu(IV) by nitrous acid and hydrogen peroxide, the oxidation of Pu(III) by nitrate and hydroxyl radicals, and the sequential oxidation of Pu(IV) to Pu(V) and Pu(VI) by the remaining available yield of nitrate radicals.

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

Electronic and optical properties of plutonium metal and oxides from Reflection Electron Energy Loss Spectroscopy

Reflection Electron Energy Loss Spectra (REELS) have been acquired on plutonium δ-Pu-Ga alloys, α-Pu 2 O 3 and PuO 2 . The position of the peaks attributable to the Pu 6p excitation can be used as ‘fingerprint’ for these species. X-ray Photoelectron Spectroscopy has been used to aid interpretation of the REELS spectra. The band gap of PuO 2 was determined from the onset of the energy loss in the REELS spectrum. The REELS data have been evaluated within the dielectric response theory by means of the QUEELS-ε(k, w)-REELS software. In this work, the Energy Loss Function, dielectric function, refractive index and extinction coefficient for these materials have been determined in the ultraviolet and extreme ultraviolet range and are compared to previously reported results.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Spectrophotometers for plutonium monitoring in HB-line

This report describes the equipment, control software, calibrations for total plutonium and plutonium oxidation state, and qualification studies for the instrument. It also provides a detailed description of the uncertainty analysis, which includes source terms associated with plutonium calibration standards, instrument drift, and inter-instrument variability. Also included are work instructions for instrument, flow cell, and optical fiber setup, work instructions for routine maintenance, and drawings and schematic diagrams.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Planning for Receipt of Mk-18A Recovered Nuclear Material at Oak Ridge National Laboratory

Oak Ridge National Laboratory (ORNL) ships and receives a wide variety of radioisotopes. These shipments will include the Mark-18A high-burnup targets, which are being processed at Savannah River National Laboratory to recover valuable isotopes that will then be shipped to ORNL for programmatic use. The Mark-18A targets will be processed to recover two products: a plutonium oxide stream and an oxide material that will contain the americium, curium, and lanthanides. A Type A shipping package has been designed, fabricated, and certified to transport the americium/curium/lanthanide oxide product in special form capsules. The package was designed with both gamma and neutron shielding for contents reading up to 5,000 R/hour. The plutonium stream will be shipped to ORNL in a Model 9975 Type B transport cask. A new content envelope for the Type B cask is being developed. This paper discusses the preparation underway at ORNL to receive the packages and transfer the material into hot cell processing and storage facilities for subsequent use in research and development applications and as feedstock for heavy actinide production.

Patton, Bradley↗
DOE OSTI2019

MIS High-Purity Plutonium/Uranium Oxide Hydride Product 5501407 (SSR129): Final Report

A high-purity uranium/plutonium mixed oxide material from the Material Identification and Surveillance (MIS) Program inventory has been studied with regard to gas generation and corrosion in a storage environment. Sample 5501579 represents process plutonium oxides from high purity mixed oxides and mixed oxides from alloy oxidation at Hanford, hydride oxide from Rocky Flats, and mixed oxides from alloy oxidation and scrap mixed oxides at Savannah River that are currently stored in 3013 containers. This study followed over time the gas pressure of two samples of this material 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. The first experiment studied a mixture of 60% as-received material (AR) and 40% material that had been calcined at 950 °C. The mixture contained 66% weapons grade plutonium and 11% uranium, with approximately 7.3% impurities and the remainder principally oxygen. A second experiment studied material calcined at 950 °C which contained approximately 4.3% impurities and similar uranium and plutonium content. Gas compositions were measured periodically over approximately 3.5 years in the first container and 20 months for the second container, which was terminated early due to an inadvertent container pumpdown. The maximum observed gas pressures were 152 kPa and 161 kPa, respectively. The increase over the initial pressures of 82 kPa and 88 kPa, respectively, was primarily due to generation of carbon dioxide and nitrogen gases. In the container with the AR/calcined mixture, a small amount of hydrogen and oxygen was generated and was consumed. In the container with calcined material only, hydrogen partial pressure of 18.9 kPa was measured. A small amount of oxygen was generated and was consumed. At the completion of the study, the internal components of both sealed containers showed signs of corrosion

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Probing the thermal decomposition of plutonium (III) oxalate with IR and Raman spectroscopy, X-ray diffraction, and electron microscopy

The thermal decomposition of Pu(III) oxalate was analyzed by Raman microspectroscopy, infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction. These data show that crystalline Pu 2 (C 2 O 4 ) 3 •9H 2 O progressively loses water and oxalate ligands as it is heated, which leads to a decrease in long-range lattice ordering, though minimal changes are observed in gross crystalline morphology. The onset of PuO 2 formation was observed between 200 - 250 °C. Thermal decomposition of oxalate ligands leads to the formation of CO 2 and plutonium oxalate-carbonate moieties, which had not been observed in previously published thermogravimetric measurements of Pu(III) oxalate. Formation of plutonium oxalate-carbonate moieties is believed to be associated with a change in the plutonium oxidation state from 3+ to 4+, which occurs prior to PuO 2 formation. The data provided herein demonstrate the rich spectroscopic nature of a rather underexplored, and technologically relevant, plutonium system. Ideally these results will further future investigations into the Pu(III) oxalate system both experimentally and computationally.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Literature review for oxalate oxidation processes and plutonium oxalate solubility

A literature review of oxalate oxidation processes finds that manganese(II)-catalyzed nitric acid oxidation of oxalate in precipitate filtrate is a viable and well-documented process. The process has been operated on the large scale at Savannah River in the past, including oxidation of 20 tons of oxalic acid in F-Canyon. Research data under a variety of conditions show the process to be robust. This process is recommended for oxalate destruction in H-Canyon in the upcoming program to produce feed for the MOX facility. Prevention of plutonium oxalate precipitation in filtrate can be achieved by concentrated nitric acid/ferric nitrate sequestration of oxalate. Organic complexants do not appear practical to sequester plutonium. Testing is proposed to confirm the literature and calculation findings of this review at projected operating conditions for the upcoming campaign.

HB-line↗
DOE OSTI2022

Potential safety impacts associated with production of gaseous PuF 6 due to reactions between 3013-compliant PuO 2 with Novec TM 1230 at temperature

A part of the NNSA/SRNS Surplus Plutonium Disposition (SPD) project is a planned expansion of an existing facility with capabilities to handle, process, package, and characterize large amounts of plutonium oxide materials for permanent disposition at WIPP. The facility design for this future processing capability will include glovebox operations, HEPA filters, and exhaust/ventilation systems. An NNSA review of the facility support systems included comments on the potential residual reactivity of previously-stabilized PuO 2 , and on the possibility of chemical interactions between stabilized PuO 2 and a new fire suppressant (Novec TM 1230), a replacement for chlorinated/brominated compounds such as HALON TM , to be employed in the event of a room/glovebox fire where PuO 2 will be processed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Computational insights into the structure of anhydrous Pu(III) oxalate

Despite the plutonium oxalate method's wide use in plutonium reprocessing, the method's mechanistic details remain unclear, particularly the identity of the plutonium oxidation state during conversion from an oxalate hydrate to the oxide. Recently, the optical vibrational spectra of Pu(III) oxalate during calcination were measured, providing an experimental reference for computational studies aimed at elucidating the oxalate structure. Here, in this work, we compare the vibrational and electronic properties of two candidate anhydrous Pu(III) oxalate structures calculated using density functional theory with recent experiments. We find that both structures are plausible and may coexist at experimental temperatures, providing insights into the broad features measured in the Raman and infrared spectra.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗