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- Harry Reid Center (8)
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Articles 1 - 14 of 14
Full-Text Articles in Nuclear Engineering
Electrochemical Approaches To Life-Support Resources In Space Missions And Nuclear Technologies: Hydrogen Peroxide And Uranium Films, Armando Manuel Pena-Duarte
Electrochemical Approaches To Life-Support Resources In Space Missions And Nuclear Technologies: Hydrogen Peroxide And Uranium Films, Armando Manuel Pena-Duarte
Open Access Theses & Dissertations
Space race has developed several technological advances that have achieved and continue to achieve the success of space missions in the aerospace timeline. Currently, the number of space technical and scientific innovations is still growing––demanding new materials and developments for extreme performing applications of fuel cells, batteries, supercapacitors, and systems of nuclear energy. Space missions require life-support solutions, auto-sustainable closed-loop living environments, cleaning and sanitizing solutions against pathogens, and safe nuclear-based resources of energy––with fissile materials with well-controlled dimensions within the core fuel elements. Likewise, to guarantee safety conditions, reduce costs, and facilitate operational logistics, space missions must reduce their …
Microstructure-Informed Modeling Of Hydrogen Diffusion In Zirconium Polycrystals, Alireza Tondro
Microstructure-Informed Modeling Of Hydrogen Diffusion In Zirconium Polycrystals, Alireza Tondro
Electronic Thesis and Dissertation Repository
Zirconium alloys are widely used in the core of various types of nuclear reactors. During service, the hot water coolant reacts with zirconium and releases hydrogen atoms that ingress into the lattice of the metal alloy. With time, hydrogen concentration exceeds its terminal solid solubility limit in zirconium, and a brittle phase known as zirconium hydride forms. This phase severely deteriorates the mechanical properties of zirconium alloys, leading to safety concerns regarding the integrity of nuclear pressure tubes. This thesis uses a crystal plasticity finite element model coupled with diffusion equations to study the effects of localized deformation at the …
A Dislocation-Based Crystal Plasticity Model For Hexagonal Close-Packed Polycrystals, Omid Sedaghat
A Dislocation-Based Crystal Plasticity Model For Hexagonal Close-Packed Polycrystals, Omid Sedaghat
Electronic Thesis and Dissertation Repository
Due to their low neutron absorption cross-section and good corrosion properties, zirconium and its alloys have been widely used as the structural material in the core of nuclear reactors. These alloys are exposed to an intensive neutron flux which may lead to dimensional instabilities and the degradation of the mechanical properties of the alloy over the service time of the reactor. The changes in deformation behavior and mechanical properties can be traced back to the formation, evolution, and interaction of the irradiation-induced microstructural defects, e.g., point defect clusters, dislocation loops, and complex dislocation line networks. However, the materials constitutive models …
Modeling Of Dislocation Channel Formation And Evolution In Irradiated Metals, Peter James Doyle
Modeling Of Dislocation Channel Formation And Evolution In Irradiated Metals, Peter James Doyle
Masters Theses
Defect-free dislocation channel formation has been reported to promote plastic instability during tensile testing via localized plastic flow, leading to a distinct loss of ductility and strain hardening in many low-temperature irradiated materials. In order to study the underlying mechanisms governing dislocation channel width and formation, the channel formation process is modeled via a simple stochastic dislocation-jog process dependent upon grain size, defect cluster density, and defect size. Dislocations traverse a field of defect clusters and jog stochastically upon defect interaction, forming channels of low defect-density. Based upon prior molecular dynamics (MD) simulations and in-situ experimental transmission electron microscopy (TEM) …
Development And Application Of 3-D Fuel Performance Modeling To Assess Missing Pellet Surface Influence On Pellet Clad Interaction And Clad Failure, Nathan Allen Capps
Development And Application Of 3-D Fuel Performance Modeling To Assess Missing Pellet Surface Influence On Pellet Clad Interaction And Clad Failure, Nathan Allen Capps
Doctoral Dissertations
In the late 1970s PCI related failures caused the implementation of startup ramp restrictions. These ramp restrictions where intended to reduce the stresses caused by pellet cladding contact. These ramp restrictions had a significant impact on Westinghouse fueled PWRs, reducing PCI related failure until 2003. Through investigation into these fuel rod failures lead to the conclusion that missing pellet surfaces (MPS) were the root cause of the failures. MPS are local geometric defects in nuclear fuel pellets that result from pellet mishandling or the manufacturing process. The presence of MPS defects can cause stress concentrations in the clad of sufficient …
Modeling And Experimental Investigation On The Influence Of Radiation Defects On Helium Behavior In Bcc Iron, Zuya Huang
Modeling And Experimental Investigation On The Influence Of Radiation Defects On Helium Behavior In Bcc Iron, Zuya Huang
Masters Theses
Fe-based alloys are important structural materials for both fission and fusion energy. For fusion applications, the challenges of radiation-induced changes in microstructure, properties and performance is further challenged by the concomitant production of helium from (n, alpha) nuclear reactions and fusion reactions. Due to the lack of a volumetric, high flux 14-MeV neutron source, studying these phenomena require the use of computational materials modeling and novel experimental methods. In this thesis, molecular dynamics (MD) simulations was used to investigate the synergistic interactions of helium with prismatic dislocation loops characteristic of those observed in neutron irradiated iron to determine how the …
Stress Corrosion Cracking And Hydrogen Embrittlement Of Martensitic Alloy Ep-823, Mohammad K. Hossain
Stress Corrosion Cracking And Hydrogen Embrittlement Of Martensitic Alloy Ep-823, Mohammad K. Hossain
UNLV Theses, Dissertations, Professional Papers, and Capstones
This investigation is focused on the evaluation of stress corrosion cracking (SCC), localized corrosion, and hydrogen embrittlement (HE) susceptibility of martensitic Alloy EP-823 in neutral and acidic solutions at ambient and elevated temperatures. While no failures were observed in smooth specimens in the neutral solution, failures were noticed in the 90°C acidic solution at constant-load (CL) leading to a threshold stress (O'th) of 102 ksi. The presence of a notch reduced the O'th value to 91 ksi in a similar environment. The ductility (%El and %RA), time-to-failure (TTF), and true failure stress (O'r) were gradually …
Stress Corrosion Cracking Resistance Of Martensitic Stainless Steels For Transmutation Applications, Phani P. Gudipati
Stress Corrosion Cracking Resistance Of Martensitic Stainless Steels For Transmutation Applications, Phani P. Gudipati
UNLV Theses, Dissertations, Professional Papers, and Capstones
The susceptibility of Alloy EP-823 to stress corrosion cracking has been evaluated using smooth and notched cylindrical specimens in neutral and acidic solutions at ambient and elevated temperatures using constant load and slow strain rate testing (SSR) techniques. C-ring and U-bend specimens have also been tested in the acidic solution. The effect of hydrogen on the cracking susceptibility has been evaluated under controlled cathodic potential. While no failures were observed with smooth specimens at constant load, the notched specimens showed failure. The SSR test results indicate that the true failure stress (o'f), time to failure and ductility parameters …
Cfd Analysis Of 3-D Thermalhydraulics Flow Effects On Wall Concentration Gradient Profiles For Lbe Loop Fittings, Narain Armbya
Cfd Analysis Of 3-D Thermalhydraulics Flow Effects On Wall Concentration Gradient Profiles For Lbe Loop Fittings, Narain Armbya
UNLV Theses, Dissertations, Professional Papers, and Capstones
The objective of the thesis is to study the effects of thermalhydraulics flows on the wall concentration gradient profiles in LBE loop fittings. To that end detailed models of the fittings have been constructed to study these effects. These fittings include sudden expansion, sudden contraction, t-joint and elbow. The typical flow rates chosen for these simulations are typical of design criteria chosen for the loop with Reynolds numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions, which include detailed …
Embrittlement And Localized Corrosion In Alloy Ht-9, Sudheer Sama
Embrittlement And Localized Corrosion In Alloy Ht-9, Sudheer Sama
UNLV Theses, Dissertations, Professional Papers, and Capstones
This investigation is focused on the evaluation of stress corrosion cracking (SCC), hydrogen embrittlement (HE) and localized corrosion susceptibility of Alloy HT -9 in neutral and acidic solutions at 30, 60 and 90°C. Constant-load and slow-strain-rate (SSR) testing techniques were used to evaluate the SCC and HE behavior of this alloy by using smooth and notched tensile specimens. Hydrogen effect on the cracking behavior was evaluated by applying cathodic (negative) potential to the test specimens. Localized corrosion susceptibility was evaluated by cyclic potentiodynamic polarization technique. The results of constant load SCC testing showed a threshold stress at 80% of the …
Environment-Induced Degradations In A Target Structural Material For Transmutation Applications, Ramprashad Prabhakaran
Environment-Induced Degradations In A Target Structural Material For Transmutation Applications, Ramprashad Prabhakaran
UNLV Theses, Dissertations, Professional Papers, and Capstones
This investigation is focused on the evaluation of stress corrosion cracking (SCC) and localized corrosion behavior of Type 422 stainless steel in aqueous environments at ambient and elevated temperature. The results of constant load SCC testing using smooth specimens showed no failure in the neutral solution but a threshold stress of 97 ksi was observed in the 90°C acidic environment. SCC testing by the slow-strain-rate test method indicate that the time-to-failure, true failure stress and ductility parameters were gradually reduced with increasing temperature, showing more pronounced effect in the acidic solution. The application of a controlled cathodic potential showed further …
Modeling, Optimization, And Flow Visualization Of Chemical Etching Process In Niobium Cavities, Sathish K. Subramanian
Modeling, Optimization, And Flow Visualization Of Chemical Etching Process In Niobium Cavities, Sathish K. Subramanian
UNLV Theses, Dissertations, Professional Papers, and Capstones
Niobium cavities are important component of the linear accelerators. Researchers have concluded that buffered chemical polishing on the inner surface of the cavity improves its performance. However the mechanism of chemical polishing is not well understood. A finite element computational fluid dynamics (CFD) model was developed to simulate the fluid flow characteristics of chemical etching process inside the cavity. The CFD model is then used to optimize the baffle design. The analysis confirmed the observation of other researchers that the iris section of the cavity received more etching than the equator regions. The baffle, which directs flow towards the walls …
Chemical Kinetics And Thermal Hydraulics Of Lead Bismuth Flow Loops, Kanthi Kiran Dasika
Chemical Kinetics And Thermal Hydraulics Of Lead Bismuth Flow Loops, Kanthi Kiran Dasika
UNLV Theses, Dissertations, Professional Papers, and Capstones
The objective of the thesis is to study the effect of chemical kinetics and thermal hydraulics of Lead Bismuth Eutectic (LBE) flow in the Materials Test Loop (MTL). The Materials Test Loop, also known as the Delta Loop, was built in Los Alamos National Laboratories (LANL) to obtain the experimental data for corrosion estimation and analysis. It is a well-known fact that corrosion plays an important role in the design of nuclear thermal hydraulic systems. Since the MTL is a multi-section closed system that differs in diameter from one part to another, an intensive study on the overall and regional …
Study Of Geometric Effects On Local Corrosion Rates For Lbe Loop, Chao Wu
Study Of Geometric Effects On Local Corrosion Rates For Lbe Loop, Chao Wu
UNLV Theses, Dissertations, Professional Papers, and Capstones
Corrosion is an extremely important issue in nuclear cooling system applications. Many scientific and engineering efforts have been contributed to the research of finding an ideal material, which has resistance to corrosive Lead Bismuth Eutectic (LBE). A Delta Loop was designed and constructed in Los Alamos National Lab (LANL) to obtain the experimental data. This loop is a multi-section closed system that differs in diameter from one part to another. As a result, an intensive study on the geometry effect is hence necessary and valuable. In this thesis, this problem was simulated by commercial software STAR-CD. Results provide a good …