Recursos de colección

DSpace at MIT (104.280 recursos)

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Nuclear Engineering - Ph.D. / Sc.D.

Mostrando recursos 1 - 20 de 496

  1. Further development of the miniaturized disk bend test approach for post-irradiation mechanical property testing

    Sohn, Dong-Seong
    by Dong-Seong Sohn.

  2. Characterization and mitigation of crud at pressurized water reactor conditions

    Dumnernchanvanit, Ittinop
    The nuclear industry is no exception when it comes to those affected by fouling deposit problems. Fouling deposits on fuel rods in nuclear reactors, known as crud, can cause a variety of undesirable effects including axial power shifts, accelerated corrosion, increased primary circuit radiation dose, and possible fuel failure. This study revisits the crud problem once again using a newly constructed Internally Heated Testloop For PWRs (IHTFP) and new analytical techniques, and attempt to find a way to prevent or mitigate crud, or at least better understand it. This is the first time that fuelrod coatings are examined as a...

  3. Spatial distribution of the neutron flux on the surfaces of a graphite-lined cavity

    Madell, J. T
    by John Thomas Madell.

  4. The use of experiments on a single fuel element to determine the nuclear parameters of reactor lattices,

    Pilat, E. E., 1937-
    Edward Ernest Pilat.

  5. Use of neutron absorbers for the experimental determination of lattice parameters in subcritical assemblies.

    Harrington, Joseph, III
    Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1966.

  6. Nuclear warhead monitoring : a study of photon emissions from fission neutron interactions with high explosives as a tool in arms control verification

    Snowden, Mareena Robinson
    Since the signing of the Nuclear Nonproliferation Treaty, the technical community has been working to develop verification options that provide confidence in the reduction or elimination of nuclear warheads, while respecting countries' requirement of limited access to national secrets. This dissertation used a simplified open-source warhead model as a vehicle to investigate the use of secondary gammas, generated passively by neutron interactions inside high explosive (HE), as a signature for the presence of a warhead-like object. Analytical calculations were done to estimate the detectability of radiative capture and inelastic scatter emissions generated within the warhead model. Results showed the emission...

  7. Development and analysis of high order neutron transport-depletion coupling algorithms

    Josey, Colin
    The coupling of depletion and neutron transport together creates a particularly challenging mathematical problem. Due to the stiffness of the ODE, special algorithms needed to be developed to minimize the number of transport simulations required. In addition, for stochastic transport, both the time step and the number of particles per time step need to be considered. In recent years, many new coupling algorithms have been developed. However, relatively little analysis of the numeric and stochastic convergence of these techniques has been performed. In this document, several new algorithms are introduced. Some are improvements of current techniques, some are taken from...

  8. Experimental and modelling studies of pit-to-crack transition under corrosion fatigue conditions

    Huang, Xuejun, Ph. D. Massachusetts Institute of Technology
    Corrosion fatigue cracking is a material degradation mechanism which occurs when materials are under cyclic loading and in a corrosive environment. The joint effect of both mechanical and environmental factors makes it one of the most challenging topics in the study of material degradation. The corrosion fatigue cracking process can be separated into four phases, namely development of crack initiation sites (e.g. film breakdown, compositional inhomogeneity, processing variables), development of crack precursors (e.g. pit initiation/growth, grain boundary or localized corrosion), short crack growth and long crack growth. While the mechanism in the long crack growth regime is relatively well understood,...

  9. A robust momentum closure approach for multiphase computational fluid dynamics applications

    Sugrue, Rosemary M
    Multiphase computational fluid dynamics (M-CFD) modeling approaches allow for the prediction of critical three-dimensional thermal-hydraulics phenomena in nuclear reactor applications. The advancement and consistent adoption of such tools could transform the industry's approach to the design of reliable systems, and the efficient operation of systems existing, which in the past have been dependent upon correlation-based sub-channel analysis codes. The success of these M-CFD methods in simulating two-phase flow and boiling heat transfer depends on their demonstrated accuracy and robustness, which signals a dual need for the comprehensive analysis of existing data and a reevaluation of the underlying physics. By virtue...

  10. Energy partition in magnetic reconnection and kinetic turbulence in weakly collisional plasmas

    Willmott, Christopher Edward
    This thesis presents the results of two studies detailing the dissipation of energy in magnetic reconnection and decaying turbulence in weakly collisional plasmas. One of the open questions regarding magnetic reconnection is how magnetic energy is dissipated into particle heating, kinetic energy, and supra-thermal particle acceleration; an understanding of energy partition in reconnection may be used to explain numerous physical phenomena such as the turbulent heating of the solar wind and the formation of high-energy astrophysical jets. We find the plasmoid dominated regime results in the formation of magnetised collisionless shocks which cause strong particle heating and the formation of...

  11. Reactor agnostic multi-group cross section generation for fine-mesh deterministic neutron transport simulations

    Boyd, William Robert Dawson, III
    A key challenge for full-core transport methods is reactor agnostic multi-group cross section (MGXS) generation. Monte Carlo (MC) presents the most accurate method for MGXS generation since it does not require any approximations to the neutron flux. This thesis develops novel methods that use MC to generate the fine-spatial mesh MGXS that are needed by high-fidelity transport codes. These methods employ either engineering-based or statistical clustering algorithms to accelerate the convergence of MGXS tallied on fine, heterogeneous spatial meshes by Monte Carlo. The traditional multi-level approach to MGXS generation is replaced by full-core MC calculations that generate MGXS for multi-group...

  12. Acceleration methods for Monte Carlo particle transport simulations

    Li, Lulu, Ph. D. Massachusetts Institute of Technology
    Performing nuclear reactor core physics analysis is a crucial step in the process of both designing and understanding nuclear power reactors. Advancements in the nuclear industry demand more accurate and detailed results from reactor analysis. Monte Carlo (MC) eigenvalue neutron transport methods are uniquely qualified to provide these results, due to their accurate treatment of space, angle, and energy dependencies of neutron distributions. Monte Carlo eigenvalue simulations are, however, challenging, because they must resolve the fission source distribution and accumulate sufficient tally statistics, resulting in prohibitive run times. This thesis proposes the Low Order Operator (LOO) acceleration method to reduce...

  13. Experimental data analysis techniques for validation of Tokamak impurity transport simulations

    Chilenski, Mark Alan
    This thesis presents two new techniques for analyzing data from impurity transport experiments in magnetically confined plasmas, with specific applications to the Alcator C-Mod tokamak. The objective in developing these new techniques is to improve the quality of the experimental results used to test simulations of turbulent transport: better characterization of the uncertainty in the experimental results will yield a better test of the simulations. Transport codes are highly sensitive to the gradients of the background temperature and density profiles, so the first half of this thesis presents a new approach to fitting tokamak profiles using nonstationary Gaussian process regression....

  14. The role of grain boundary character in hydrogen embrittlement of nickel-iron superalloys

    Hanson, John Paul, Ph. D. Massachusetts Institute of Technology
    Hydrogen embrittlement of engineering alloys is characterized by a loss of ductility and unpredictable failure. These failures affect numerous industries, including nuclear power, oil and gas exploration, and hydrogen transportation and storage. In face-centered cubic alloys, the resultant fracture is intergranular and very sensitive to grain boundary character. We study this behavior in alloy 725, a popular nickel-iron superalloy with high strength and corrosion resistance. Using a suite of complementary experimental techniques we reveal the fracture behavior of individual grain boundaries in hydrogen embrittlement for the first time, providing critical understanding of the role of grain boundary character and informing...

  15. Methods for including multiphysics feedback in Monte Carlo reactor physics calculations

    Ellis, Matthew Shawn
    The ability to model and simulate nuclear reactors during steady state and transient conditions is important for designing efficient and safe nuclear power systems. The accurate simulation of a nuclear reactor is particularly challenging because the multiple physical processes within the reactor are tightly coupled, which requires that the numerical methods used to resolve each physical process can accurately and efficiently transfer and utilize data from other applications. Monte Carlo methods are desirable for solving the neutron transport equation required in reactor analysis because of the inherent accuracy of the method, but the Computational Solid Geometry (CSG) representation of the...

  16. Modeling and simulation of liquid microlayer formation and evaporation in nucleate boiling using computational fluid dynamics

    Guion, Alexandre Nicolas
    The transport of latent heat makes boiling one of the most efficient modes of heat transfer, allowing a wide range of systems to improve their thermal performance, from microelectronic devices to nuclear power plants. In particular, Boiling Water Reactors (BWR) use boiling as the primary mode of heat transfer in the reactor core to accommodate very high heat fluxes. In Pressurized Water Reactors (PWR) subcooled flow boiling can occur in hot sub-channels. As a bubble grows outside of a surface imperfection during nucleate boiling, viscous stresses at the wall can be strong enough to impede liquid motion and trap a...

  17. Studies on hydration water dynamics and microstructure of synthetic cement

    Le, Peisi, Ph. D. Massachusetts Institute of Technology
    The mechanical properties of cement pastes depend strongly on their porosities. In a wet paste, the porosity links to the free water volume after hydration. Structural water which presents in the solid phase, constrained water absorbed on the surface of the pores and free water in the center of the pores have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. We investigated the dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS). C-S-H and M-S-H are the chemical binders...

  18. Fluoride-salt-cooled high-temperature test reactor thermal-hydraulic licensing and uncertainty propagation analysis

    Romatoski, Rebecca R. (Rebecca Rose)
    An important Fluoride-salt-cooled High-temperature Reactor (FHR) development step is to design, build, and operate a test reactor. Through a literature review, liquid-salt coolant thermophysical properties have been recommended along with their uncertainties of 2-20%. This study tackles determining the effects of these high uncertainties by proposing a newly developed methodology to incorporate uncertainty propagation in a thermal-hydraulic safety analysis for test reactor licensing. A hot channel model, Monte Carlo statistical sampling uncertainty propagation, and limiting safety systems settings (LSSS) approach are uniquely combined to ensure sufficient margin to fuel and material thermal limits during steady-state operation and to incorporate margin...

  19. Characterization of the dynamic formation of nano-tendril surface morphology on tungsten while exposed to helium plasma

    Woller, Kevin Benjamin
    Tungsten undergoes surface morphology changes on the nanometer scale when subjected to low energy helium ion bombardment. This is due in part to the ion bombardment causing tungsten atoms to move on the surface, but also because of helium implantation and bubble development in the near surface at a depth < 30 nm. At high enough surface temperatures, T/TM >/~ 0.2, where TM is the melting temperature, nanoscale tendrils form on the surface and grow longer with additional bombardment by helium, but will decompose at the same temperature without helium bombardment. A tungsten surface that develops a densely packed layer...

  20. Coherent control of electron spins in diamond for quantum information science and quantum sensing

    Cooper-Roy, Alexandre
    This thesis introduces and experimentally demonstrates coherent control techniques to exploit electron spins in diamond for applications in quantum information processing and quantum sensing. Specifically, optically-detected magnetic resonance measurements are performed on quantum states of single and multiple electronic spins associated with nitrogen-vacancy centers and other paramagnetic centers in synthetic diamond crystals. We first introduce and experimentally demonstrate the Walsh reconstruction method as a general framework to estimate the parameters of deterministic and stochastic fields with a quantum probe. Our method generalizes sampling techniques based on dynamical decoupling sequences and enables measuring the temporal profile of time-varying magnetic fields in...

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