Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “post”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Post-irradiation examination to assess performance and safety of nuclear fuel

This work presents some results from testing campaigns performed at JRC-ITU on irradiated fuels and analogues aimed at characterizing fuel alterations during and after irradiation. The characterization of local structural and property changes is the first step towards the description of the overall behaviour of the fuel, including safety- and performance-relevant properties. High burnup light water reactor (LWR) UO{sub 2} fuel (= 60 GWd/tHM) was used for morphology and mechanical property studies. Radial profiles of porosity obtained from scanning electron microscopy image analysis were compared with corresponding sub-surface data obtained using acoustic microscopy. An increase of porosity was observed at the rim of the pellet in correspondence with the high burnup structure (HBS), and also at intermediate radius locations in correspondence with the occurrence of the so-called dark zone. This zone is characterized by several features similar to the HBS: in addition to increased local porosity, grain subdivision features were observed. The examination of grain free surface morphology along the pellet radius revealed the onset of surface alteration which resulted in almost complete loss of the original grain shape in conjunction with the formation of the dark zone. Additionally, possible ageing effects due to accumulation of microstructural decay damage during storage were investigated and compared to the results obtained under accelerated ageing conditions using alpha-doped analogues. Similar hardening trends were observed by comparing the hardness evolution as a function of accumulated damaged in unirradiated analogues and spent fuel. No significant hardness increase was observed on the same high burnup/high dose spent fuel after >10 years of additional storage in hot cell, confirming that hardening saturates at a damage level near 0.1 dpa. These experimental campaigns contribute establishing a basis of data for further analysis, in combination with suitable modelling tools. The final goal is to achieve the full scientific understanding of mechanisms and processes affecting fuel properties and behaviour, as a necessary step to establish the basis for developing advanced fuel systems with optimized performance and safety. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Plan for Post-Irradiation Examination of Zion Reactor Pressure Vessel Beltline Materials

The reactor pressure vessel (RPV) is a potentially life-limiting component in light-water reactors (LWR) because replacement of the RPV is not considered a viable option. Researchers studying the effects of radiation on RPV materials have long been interested in evaluating service-irradiated materials to assess currently available models for predicting radiation embrittlement of RPV steels. The decommissioning of the Zion Unit 1 NPP in Zion, Illinois presents a unique opportunity for characterization of an actual reactor pressure vessel (RPV) material after inservice degradation. The main interests in this case are the belt-line weld and base metals. Through-RPV wall thickness attenuation and chemical composition distributions are the obvious objectives of this characterization program. However, it also provides an opportunity to examine the inservice degradation and its comparison with currently available models for prediction of radiation embrittlement of RPV steels. All of these efforts will provide a better understanding of materials degradation and other issues associated with extending the lifetime of existing NPPs beyond 60 years of service. The primary foci are the Linde 80 flux, wire heat 72105 (WF-70) circumferential belt-line weld and the A533B-1 base metal from the intermediate shell harvested from a region of peak fluence (0.7 x 10{sup 19} n/cm{sup 2}, E > 1.0 MeV) on the internal surface of the Zion Unit 1 vessel. Following determination of the through-thickness chemical composition, Charpy impact, fracture toughness, tensile, and hardness testing will be being performed to characterize the through-thickness mechanical properties of the base metal and belt-line-weld materials. In addition to mechanical properties, microstructural characterizations will be performed using various techniques, including Atom Probe Tomography, Small Angle Neutron Scattering, and Positron Annihilation Spectroscopy.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Post-Irradiation Examination for Conventional and Advanced Nuclear Fuel

During irradiation in a nuclear reactor, the fuel pellet experiences non-uniform fission rate and strong thermomechanical loads, which result in alterations and restructuring occurring non-homogeneously in the fuel volume. The irradiated fuel is characterized by a highly heterogeneous structure, with a correspondingly heterogeneous distribution of phases and properties. It is a big technical challenge for a hot cell facility to be able to cover effectively a broad variety of fuel types and compounds, characterized by different compositions, physico-chemical properties, geometries and configurations. The first challenge is to provide testing environments and procedures which do not alter or degrade the original irradiated fuel properties and are technically suitable for hot cell or shielded facility operation. For instance, non-oxide fuel compounds require protective atmosphere to avoid sample oxidation during storage, preparation and testing. Moreover, suitable adaptations of tools and measuring devices must be available to characterize fuel configurations which differ from the conventional cylindrical pellet-cladding geometries (e.g. spherical fuel elements for pebble bed HTR and TRISO coated fuel particles). Finally, adequate scientific methods of investigation must be available to measure properties and study the behaviour of highly heterogeneous irradiated fuel. In addition to basic techniques for non-destructive and destructive examination of nuclear fuel systems (e.g. covering fuel and cladding or fuel and coatings, or other configurations), 'in-depth' methods are applied to determine physical, thermomechanical and micro-analytical properties of specific phases/features present in irradiated fuel. This paper presents relevant trends and examples from fuel safety studies performed at JRC-Karlsruhe and in other laboratories which highlight the 'added value' obtainable by applying combined techniques, high resolution tools or 3D methods of analysis for the experimental 'multiscale' characterization of irradiated fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Mathematical modeling of a moving bed reactor for post-combustion CO 2 capture

A mathematical model for a moving bed reactor with embedded heat exchanger has been developed for application to solid sorbent-based capture of carbon dioxide from flue gas emitted by coal-fired power plants. The reactor model is one-dimensional, non-isothermal, and pressure-driven. The two-phase (gas and solids) model includes rigorous kinetics and heat and mass transfer between the two phases. Flow characteristics of the gas and solids in the moving bed are obtained by analogy with correlations for fixed and fluidized bed systems. From the steady-state perspective, this work presents the impact of key design variables that can be used for optimization. From the dynamic perspective, the article shows transient profiles of key outputs that should be taken into account while designing an effective control system. Additionally, the article also presents performance of a model predictive controller for the moving bed regenerator under process constraints.

42 ENGINEERING↗
DOE OSTI2021

In-situ observation of pre-, co- and post-seismic shear slip at 1.5 km depth

Understanding the initiation and arrest of earthquakes is one of the long-standing challenges of seismology. Here we report on direct observations of borehole displacement by a meter-sized shear rupture induced by pressurization of metamorphic rock at 1.5 km depth. We observed the acceleration of sliding, followed by fast co-seismic slip and transient afterslip. Total displacements were about 7, 5.5 and 9.5 micrometers, respectively for the observed pre-slip, co-seismic slip and afterslip. The observed pre-slip lasted about 0.4 seconds. Co-seismic slip was recorded by the 1 kHz displacement recording and a 12-component array of 3-C accelerometers sampled at 100 kHz. The observed afterslip is consistent with analytical models of arrest in a velocity-strengthening region and subsequent stress relaxation. < p >The observed slip vector agrees with the activation of a bedding plane within the phyllite, which is corroborated by relocated seismic events that were observed during the later stages of the injection experiment.

Schoenball, Martin↗
DOE OSTI2018

An Efficient Post-Polymerization Modification of Poly(Styrene- co -Maleic Anhydride) for Thermally Reversible Nanocomposites

A copolymer of maleic anhydride and styrene is functionalized with Diels–Alder (DA) capable pendant groups to enable the study of this material with different crosslink densities. This constituent is synthesized using commercially available starting materials and relatively simple and uncomplicated chemistries which open the possibility for its use in large-scale applications. The 10%, 25%, 50%, and 100% DA nominal crosslinking based on available pendant furan groups on the polymeric component is investigated. The reaction kinetics are monitored using infrared spectroscopy and rheology. Based on the rheological results, carbon nanotube (CNT) incorporation into the DA matrix is explored in order to determine its effects on the complex modulus of the material. This work done in this report is meant as a proof of concept for this DA material with the possibility of its incorporation into other commonly used bulk materials and/or adhesives to allow for an easily reversible product formulation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Visualization of Hemispherical Post‐Detonation Fireball Internal Structures

Hemispherical charges are initiated above a transparent plate in a half‐plane configuration, allowing optical access to the internal regions of the luminous fireball. High‐speed visualization enables characterization of the internal luminous structure, showing clearly the bright shell and dark core regions. Spectroscopic and pyrometric diagnostics are applied to these flows, generating quantitative information on the spatial distribution of temperature inside the fireball. Both cased and uncased charges can be examined using this methodology, and several different high explosives are tested. This approach can be useful in validation of detailed explosive fireball models. Initial comparisons with such models are presented.

detonation↗
DOE OSTI2017

Target highlights from the first post-PSI CASP experiment (CASP12, May–August 2016)

In this paper, the functional and biological significance of the selected CASP12 targets are described by the authors of the structures. Finally, the crystallographers discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP12 experiment.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Computational Nuclear Physics and Post Hartree-Fock Methods

We present a computational approach to infinite nuclear matter employing Hartree-Fock theory, many-body perturbation theory and coupled cluster theory. These lectures are closely linked with those of chapters 9, 10 and 11 and serve as input for the correlation functions employed in Monte Carlo calculations in chapter 9, the in-medium similarity renormalization group theory of dense fermionic systems of chapter 10 and the Green's function approach in chapter 11. We provide extensive code examples and benchmark calculations, allowing thereby an eventual reader to start writing her/his own codes. We start with an object-oriented serial code and end with discussions on strategies for porting the code to present and planned high-performance computing facilities.

Lietz, Justin↗
DOE OSTI2019

Usefulness of Direct Computed Tomography Venography in Predicting Inflow for Venous Reconstruction in Chronic Post-thrombotic Syndrome

Purpose: The purpose of this paper is to assess the applicability of direct computed tomography venography (DCTV) in assessing dominant inflow vein in the femoral confluence in extensive chronic iliofemoral venous obstruction, using venography as the gold standard. Methods: All DCTVs performed in symptomatic patients with previous iliofemoral deep vein thrombosis subsequently submitted to venography in the period from January 2014 to August 2018 were retrospectively reviewed. Two groups were defined depending on whether the femoral vein (FV) or the deep femoral vein (DFV) was the dominant inflow on venography in order to identify predictors of DFV as dominant inflow in DCTV. Statistical analysis was performed with SPSS V25. Results: A total of 30 DCTVs and subsequent venographies were reviewed. Venography identified the FV as the dominant inflow in 18 (60%) and the DFV in 12 (40%) patients. Predictors for DFV as dominant inflow were identified as follows: larger DFV diameter 50 mm and 250 mm below lesser trochanter (8.73 ± 4.34 mm vs. 11.9 ± 3.52 mm; p = 0.043 and 5.4 ± 3.90 mm vs. 8.90 ± 2.70 mm; p = 0.011); lower FV/DFV ratio 150 mm below lesser trochanter (11.39 ± 20.01 mm vs. 1.05 ± 0.47 mm; p = 0.043); and presence of FV scarring/synechiae, collaterals and abnormal wall thickness (p = 0.003, p = 0.003 and p < 0.0001). Conclusion: In cases of extensive chronic iliofemoral venous obstruction, especially when stent deployment into the DFV is entertained, the key to success is thorough pre-procedure planning focusing on choosing the access site. This study suggests DCTV is valuable in defining the dominant iliac vein inflow, but additional findings are necessary to validate these preliminary data.

62 RADIOLOGY AND NUCLEAR MEDICINE↗