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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Technology Advancement and Insertion into Operating Nuclear Facilities

Key challenges in the NNSA modernization effort are centered around the selection of new processing / production technologies to deploy in existing, operating, and oftentimes, aging nuclear facilities. New uranium processing technologies may offer significant improvements in worker and environmental safety, material control and accountability, and production efficiencies, but adaptation of these technologies into existing facilities presents unique (and usually, difficult) engineering solutions for each new technology. This presentation discusses approaches utilized at Y-12 to mature and demonstrate new processing and production technologies for deployment into aging nuclear facilities. The technology advancement lifecycle (from concept to deployment) of uranium electrorefining technologies will be reviewed, as a prototypical example, to describe steps and approaches utilized at Y-12 (and NNSA Sites) to (i) mature technologies and manufacturing strategies, (ii) establish testbed capabilities for full-scale process demonstrations, and (iii) reduce risks associated with operational disruptions when commissioning new uranium processing technologies.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2012

3D analysis of the reactivity insertion accident in VVER-1000

Fuel parameters such as peak enthalpy and temperature during rod ejection accident are calculated. The calculations are performed by 3D neutron kinetics code NESTLE and 3D thermal-hydraulic code VIPRE-W. Both hot zero power and hot full power cases were studied for an equilibrium cycle with Westinghouse hex fuel in VVER-1000. It is shown that the use of 3D methodology can significantly increase safety margins for current criteria and met future criteria. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

Chapter 2: Trackable Multiplex Recombineering (TRMR) and Next-Generation Genome Design Technologies: Modifying Gene Expression in E. coli by Inserting Synthetic DNA Cassettes and Molecular Barcodes

This chapter describes the trackable multiplex recombineering (TRMR) and tunable trackable multiplex recombineering (T2RMR) techniques, which not only make the multiplexing of recombineering possible in Escherichia coli but also provide the ability to track the engineered genetic changes accurately. TRMR and T2RMR have only been used for modifying the expression level of genes. Screening and selection of TRMR and T2RMR clones can be carried out using either liquid or solid media with any chemical compound that modifies growth or confers a phenotype that can be detected by a high-throughput assay. In order to engineer a genome using TRMR or T2RMR, a synthetic DNA (synDNA) cassette is created that encodes for a genetic feature and a molecular barcode that is used to track each feature. These synDNA cassettes are then introduced in parallel into cell populations via recombineering.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Highly Efficient Uniaxial In-Plane Stretching of a 2D Material via Ion Insertion

On-chip dynamic strain engineering requires efficient micro-actuators that can generate large in-plane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1 V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful “straintronic” devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe 2 causes large anisotropic in-plane strain: 5% in one in-plane direction and 0.1% in the other. This efficient stretching of the 2D WTe 2 layers contrasts to intercalation-induced strains in related materials which are predominantly in the out-of-plane direction. The unusual actuation of Li x WTe 2 is linked to the formation of a newly discovered crystallographic phase, referred to as Td', with an exotic atomic arrangement. On-chip low-voltage (<0.2 V) control is demonstrated over the transition to the novel phase and its composition. Within the Td'-Li 0.5-δ WTe 2 phase, a uniaxial in-plane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in-plane chemical expansion coefficient of Td'-Li 0.5-δ WTe 2 far greater than of any other single-phase material, enabling fast and efficient planar electrochemical actuation.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Operando Observations and First-Principles Calculations of Reduced Lithium Insertion in Au-Coated LiMn 2 O 4

The deposition of protective coatings on the spinel LiMn 2 O 4 (LMO) lithium–ion battery cathode is effective in reducing Mn dissolution from the electrode surface. Although protective coatings positively affect LMO cycle life, much remains to be understood regarding the interface formed between these coatings and LMO. Using operando powder X–ray diffraction with Rietveld refinement, it is shown that, in comparison to bare LMO, the lattice parameter of a model Au–coated LMO cathode is significantly reduced upon relithiation. Less charge passes through Au–coated LMO in comparison to bare LMO, suggesting that the reduced lattice parameter is associated with decreased Li + solubility in the Au–coated LMO. Density functional theory calculations show that a more Li + –deficient near–surface is thermodynamically favorable in the presence of the Au coating, which may further stabilize these cathodes through suppressing formation of the Jahn–Teller distorted Li 2 Mn 2 O 4 phase at the surface. Electronic structure and chemical bonding analyses show enhanced hybridization between Au and LMO for delithiated surfaces leading to partial oxidation of Au upon delithiation. Furthermore, this study suggests that, in addition to transition metal dissolution from electrode surfaces, protective coating design must also balance potential energy effects induced by charge transfer at the electrode–coating interface.

25 ENERGY STORAGE↗
DOE OSTI2018

Palladium‐Catalyzed Reductive Insertion of Alcohols into Aryl Ether Bonds

Abstract Palladium on carbon catalyzes C−O bond cleavage of aryl ethers (diphenyl ether and cyclohexyl phenyl ether) by alcohols (R−OH) in H 2 . The aromatic C−O bond is cleaved by reductive solvolysis, which is initiated by Pd‐catalyzed partial hydrogenation of one phenyl ring to form an enol ether. The enol ether reacts rapidly with alcohols to form a ketal, which generates 1‐cyclohexenyl−O−R by eliminating phenol or an alkanol. Subsequent hydrogenation leads to cyclohexyl−O−R.

Wang, Meng↗
DOE OSTI2017

Inserting Porphyrin Quantum Dots in Bottom-Up Synthesized Graphene Nanoribbons

Diels–Alder copolymerization of tetraphenylcyclopentadienone, a precursor for cove graphene nanoribbons (cGNRs), with bifunctional porphyrins yields defined nanostructures comprised of a single cGNR-porphyrin-cGNR heterojunction within each ribbon. 13 C NMR labeling and high-resolution mass spectrometry of solubilized polymer intermediates indicates that every porphyrin is covalently linked to two extended segments of cGNRs. UV/Vis absorption and fluorescence emission spectroscopy reveal a strong electronic correlation between the porphyrin and the adjacent cGNR segments that can be attenuated through reversible metalation of the porphyrin core. This versatile bottom-up synthetic strategy provides access to structurally well-defined, functional GNR-quantum dot-GNR heterostructures within a single graphene nanoribbon.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Atypical effect of temperature tuning on the insertion of the catalytic iron−sulfur center in a recombinant [FeFe]‐hydrogenase

Abstract The expression of recombinant [FeFe]‐hydrogenases is an important step for the production of large amount of these enzymes for their exploitation in biotechnology and for the characterization of the protein‐metal cofactor interactions. The correct assembly of the organometallic catalytic site, named H‐cluster, requires a dedicated set of maturases that must be coexpressed in the microbial hosts or used for in vitro assembly of the active enzymes. In this work, the effect of the post‐induction temperature on the recombinant expression of CaHydA [FeFe]‐hydrogenase in E. coli is investigated. The results show a peculiar behavior: the enzyme expression is maximum at lower temperatures (20°C), while the specific activity of the purified CaHydA is higher at higher temperature (30°C), as a consequence of improved protein folding and active site incorporation.

Morra, Simone↗