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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

DISSOLUTION AND ANALYSIS OF YELLOWCAKE COMPONENTS FOR FINGERPRINTING UOC SOURCES

There are a number of chemical and physical parameters that might be used to help elucidate the ore body from which uranium ore concentrate (UOC) was derived. It is the variation in the concentration and isotopic composition of these components that can provide information as to the identity of the ore body from which the UOC was mined and the type of subsequent processing that has been undertaken. Oak Ridge National Laboratory (ORNL) in collaboration with Lawrence Livermore and Los Alamos National Laboratories is surveying ore characteristics of yellowcake samples from known geologic origin. The data sets are being incorporated into a national database to help in sourcing interdicted material, as well as aid in safeguards and nonproliferation activities. Geologic age and attributes from chemical processing are site-specific. Isotopic abundances of lead, neodymium, and strontium provide insight into the provenance of geologic location of ore material. Variations in lead isotopes are due to the radioactive decay of uranium in the ore. Likewise, neodymium isotopic abundances are skewed due to the radiogenic decay of samarium. Rubidium decay similarly alters the isotopic signature of strontium isotopic composition in ores. This paper will discuss the chemical processing of yellowcake performed at ORNL. Variations in lead, neodymium, and strontium isotopic abundances are being analyzed in UOC from two geologic sources. Chemical separation and instrumental protocols will be summarized. The data will be correlated with chemical signatures (such as elemental composition, uranium, carbon, and nitrogen isotopic content) to demonstrate the utility of principal component and cluster analyses to aid in the determination of UOC provenance.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Evaluation of Resin Dissolution Using an Advanced Oxidation Process - 13241

The ion-exchange resin is widely used in nuclear reactors, in cooling water purification and removing radioactive elements. Because of the long periods of time inside the reactor system, the resin becomes radioactive. When the useful life of them is over, its re-utilization becomes inappropriate, and for this reason, the resin is considered radioactive waste. The most common method of treatment is the immobilization of spent ion exchange resin in cement in order to form a solid monolithic matrix, which reduces the radionuclides release into the environment. However, the characteristic of contraction and expansion of the resin limits its incorporation in 10%, resulting in high cost in its direct immobilization. Therefore, it is recommended the utilization of a pre-treatment, capable of reducing the volume and degrading the resin, which would increase the load capacity in the immobilization. This work aims to develop a method of degradation of ion spent resins from the nuclear research reactor of Nuclear and Energy Research Institute (IPEN/CNEN-SP), Brazil, using the Advanced Oxidative Process (AOP) with Fenton's reagent (hydrogen peroxide and ferrous sulphate as catalyst). The resin evaluated was a mixture of cationic (IR 120P) and anionic (IRA 410) resins. The reactions were conducted by varying the concentration of the catalyst (25, 50, 100 e 150 mM) and the volume of the hydrogen peroxide, at three different temperatures, 50, 60 and 70 deg. C. The time of reaction was three hours. Total organic carbon content was determined periodically in order to evaluate the degradation as a function of time. The concentration of 50 mM of catalyst was the most effective in degrading approximately 99%, using up to 330 mL of hydrogen peroxide. The most effective temperature was about 60 deg. C, because of the decomposition of hydrogen peroxide in higher temperatures. TOC content was influenced by the concentration of the catalyst, interfering in the beginning of the degradation process. It was possible to correlate it with the final amount of non-degraded resins. These results show that these conditions were favorable to destroy the resins, indicating to be the AOP an effective technique to reduce the volume of the waste. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Dissolution of metal oxides and separation of uranium from lanthanides and actinides in supercritical carbon dioxide

This paper investigates the feasibility of extracting and separating uranium from lanthanides and other actinides by using supercritical fluid carbon dioxide (sc-CO{sub 2}) as a solvent modified with tri-n-butylphosphate (TBP) for the development of a counter current stripping technique, which would be a more efficient and environmentally benign technology for spent nuclear fuel reprocessing compared to traditional solvent extraction. Several actinides (U, Pu, and Np) and europium were extracted in sc-CO{sub 2} modified with TBP over a range of nitric acid concentrations and then the actinides were exposed to reducing and complexing agents to suppress their extractability. According to this study, uranium/europium and uranium/plutonium extraction and separation in sc-CO{sub 2} modified with TBP is successful at nitric acid concentrations of less than 6 M and at nitric acid concentrations of less than 3 M with acetohydroxamic acid or oxalic acid, respectively. A scheme for recycling uranium from spent nuclear fuel by using sc-CO{sub 2} and counter current stripping columns is presented. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Nondisruptive Dissolution of Hyperpolarized 129 Xe into Viscous Aqueous and Organic Liquid Crystalline Environments

Studies of hyperpolarized xenon-129 (hp- 129 Xe) in media such as liquid crystals and cell suspensions are in demand for applications ranging from biomedical imaging to materials engineering but have been hindered by the inability to bubble Xe through the desired media as a result of viscosity or perturbations caused by bubbles. In this paper a device is reported that can be reliably used to dissolve hp- 129 Xe into viscous aqueous and organic samples without bubbling. This method is robust, requires small sample volumes (<60 μL), is compatible with existing NMR hardware, and is made from readily available materials. Experiments show that Xe can be introduced into viscous and aligned media without disrupting molecular order. We detected dissolved xenon in an aqueous liquid crystal that is disrupted by the shear forces of bubbling, and we observed liquid-crystal phase transitions in (MBBA). This tool allows an entirely new class of samples to be investigated by hyperpolarized-gas NMR spectroscopy.

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

Bromine Assisted MnO 2 Dissolution Chemistry: Toward a Hybrid Flow Battery with Energy Density of over 300 Wh L −1

Abstract Mn 2+ /Mn 3+ redox pair has been considered as a promising cathode for high energy density batteries, due to its attractive features of high redox potential, solubility and outstanding kinetics. However, the disproportionation side reaction of Mn 3+ , which results in accumulation of “dead” MnO 2 limits its reversibility and further energy density. Herein, a novel catholyte based on mixture of Mn 2+ and Br − was proposed for flow batteries with high energy density and long cycle life. In the design, the “dead” MnO 2 can be fully discharged via Br − by a chemical‐electrochemical reaction. Coupled with Cd/Cd 2+ as anode, the assembled Bromine‐Manganese flow battery (BMFB) demonstrates a high energy efficiency of 76 % at 80 mA cm −2 with energy density of 360 Wh L −1 . The battery assembled with silicotungstic acid as anode could continuously run for over 2000 cycles at 80 mA cm −2 . With high power density, energy density and durability, the BMFB shows great potential for large‐scale energy storage.

Chemistry↗
DOE OSTI2014

Determination of Uranium Metal Concentration in Irradiated Fuel Storage Basin Sludge Using Selective Dissolution

Uranium metal corroding in water-saturated sludges now held in the US Department of Energy Hanford Site K West irradiated fuel storage basin can create hazardous hydrogen atmospheres during handling, immobilization, or subsequent transport and storage. Knowledge of uranium metal concentration in sludge thus is essential to safe sludge management and process design, requiring an expeditious routine analytical method to detect uranium metal concentrations as low as 0.03 wt% in sludge even in the presence of 30 wt% or higher total uranium concentrations.

Nuclear fuel storage basin sludge↗
DOE OSTI2016

Dissolution of uranium oxides from simulated environmental swipes using ammonium bifluoride

We developed an analytical chemistry method to quantitatively recover microgram quanties of solid uranium oxides from swipe media using ammonium bifluoride (ABF, NH 4 HF 2 ) solution. Recovery of uranium from surrogate swipe media (filter paper) was demonstrated at initial uranium loading levels between 3 and 20 µg filter -1 . Moreover, the optimal conditions for extracting U 3 O 8 and UO 2 are using 1 % ABF solution and incubating at 80 °C for one hour. The average uranium recoveries are 100 % for U 3 O 8 , and 90 % for UO 2 . Finally, with this method, uranium concentration as low as 3 µg filter -1 can be recovered for analysis.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Dissolution of Intermetallic Second-Phase Particles in Zircaloy-2 in High-Temperature Steam

The stability of intermetallic second-phase particles (SPPs) in coated Zircaloy-2 was studied in 700 °C steam environments up to 20 hours. Hydrogen generated from high-temperature steam oxidation of uncoated Zr-induced δ-hydrides formation in the Zircaloy matrix. Synchrotron XRD demonstrated that longer exposure times increased hydride peak intensity and decreased intermetallic SPPs’ peak intensity. Cross-sectional SEM analysis verified the intermetallic SPPs’ volume fraction reduction. The size distribution of intermetallic SPPs was characterized and larger particles were dissolved at longer oxidation time. Finally, a correlation between the hydrogen concentration and the volume fraction of intermetallic SPPs at 700 °C steam environment was found, with the volume fraction of SPPs decreasing as hydrogen concentration increases.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Precipitation of Carbides and Dissolution of Widmanstätten Structure for Enhanced Hardness in Ti{sub 2}AlNb-Based Alloys

Carbide-reinforced Ti{sub 2}AlNb matrix composites were spark plasma sintered at 1100 °C by incorporating CNTs into single-B2-phase Ti-22Al-25Nb powders. The as-SPSed alloys were solution treated and then aged in different phase regions. By kinetics analysis and energy-dispersive spectroscopy, it is found carbon will stabilize α{sub 2} phase during solution treatment, and the formation of carbide results in the Nb-depleted regions, which further induces the formation of curly B2 + O Widmanstätten structure during quenching. Different from the general Widmanstätten structure in the aged Ti{sub 2}AlNb alloy, the remained α{sub 2} will consume the B2 within the Widmanstätten structure, when the carbon-added alloy is aged in B2 + O phase region. Compared to the alloy without CNTs, the Vickers hardness of the aged carbon-added Ti{sub 2}AlNb alloy is increased significantly, which is related to the uniform and abundant columnar carbides within the O-phase matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Intercritical Annealing Time at Pearlite Dissolution Finish Temperature (Ac{sub 1f}) on Mechanical Properties of Low-Carbon Dual-Phase Steel

The effect of intercritical annealing at Ac{sub 1}, Ac{sub 1f}, and Ac{sub 3} temperatures followed by water quenching was studied on the microstructure and mechanical properties of a 0.035C-0.27Mn low-carbon steel. During short-term holding at Ac{sub 1} and Ac{sub 1f}, some pearlite remained after quenching and the yield-point phenomenon was still detectable, which was related to the formation of small amount of martensite inside pearlite colonies and on ferrite grain boundaries with marginal effect on the surrounding ferrite phase. By increasing holding time at Ac{sub 1f}, pearlite disappeared and DP microstructures were achieved with the disappearance of the yield-point phenomenon and the enhancement of the work-hardening capacity. At long holding times, however, the mechanical properties deteriorated mainly due to the coarsening of martensitic islands and disappearance of dynamic strain aging (Portevin–Le Chatelier) effect at room temperature.

36 MATERIALS SCIENCE↗