<p> Accurate prediction of evaporative losses from light water reactor nuclear power plant (NPP) spent fuel storage pools (SFPs) is important for activities ranging from sizing of water makeup systems during NPP design to predicting the time available to supply emergency makeup water following severe accidents. Existing correlations for predicting evaporation from water surfaces are only optimized for conditions typical of swimming pools. This new approach modeling evaporation as a diffusion process has yielded an evaporation rate model that provided a better fit of published high temperature evaporation data and measurements from two SFPs than other published evaporation correlations. Insights from treating evaporation as a diffusion process include correcting for the effects of air flow and solutes on evaporation rate. An accurate modeling of the effects of air flow on evaporation rate is required to explain the observed temperature data from the Fukushima Daiichi Unit 4 SFP during the 2011 loss of cooling event; the diffusion model of evaporation provides a significantly better fit to this data than existing evaporation models.</p>

<p> Air bubble injection and subcooled flow boiling experiments have been performed to investigate the liquid flow field and bubble nucleation, growth, and departure, in part to contribute to the DOE Nuclear HUB project, Consortium for Advanced Simulation of Light Water Reactors (CASL). The main objective was to obtain quantitative data and compartmentalize the many different interconnected aspects of the boiling process &mdash; from the channel geometry, to liquid and gas interactions, to underlying heat transfer mechanisms. </p><p> The air bubble injection experiments were performed in annular and rectangular geometries and yielded data on bubble formation and departure from a small hole on the inner tube surface, subsequent motion and deformation of the detached bubbles, and interactions with laminar or turbulent water flow. Instantaneous and ensemble- average liquid velocity profiles have been obtained using a Particle Image Velocimetry technique and a high speed video camera. Reynolds numbers for these works ranged from 1,300 to 7,700.</p><p> Boiling experiments have been performed with subcooled water at atmospheric pres- sure in the same annular channel geometry as the air injection experiments. A second flow loop with a slightly larger annular channel was constructed to perform further boiling experiments at elevated pressures up to 10 bar. High speed video and PIV measurements of turbulent velocity profiles in the presence of small vapor bubbles on the heated rod are presented. The liquid Reynolds number for this set of experiments ranged from 5,460 to 86,000. It was observed that as the vapor bubbles are very small compared to the injected air bubbles, further experiments were performed using a microscopic objective to obtain higher spatial resolution for velocity fields near the heated wall. Multiple correlations for the bubble liftoff diameter, liftoff time and bub- ble history number were evaluated against a number of experimental datasets from previous works, resulting in a new proposed correlations that account for fluid prop- erties that vary with pressure, heat flux, and variations in geometry.</p>

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 23, 2007) Includes bibliographical references.

<p> Neutral particle radiation transport simulations are critical for radiation shielding and deep penetration applications. Arriving at a solution for a given response of interest can be computationally difficult because of the magnitude of particle attenuation often seen in these shielding problems. Hybrid methods, which aim to synergize the individual favorable aspects of deterministic and stochastic solution methods for solving the steady-state neutron transport equation, are commonly used in radiation shielding applications to achieve statistically meaningful results in a reduced amount of computational time and effort. The current state of the art in hybrid calculations is the Consistent Adjoint-Driven Importance Sampling (CADIS) and Forward-Weighted CADIS (FW-CADIS) methods, which generate Monte Carlo variance reduction parameters based on deterministically-calculated scalar flux solutions. For certain types of radiation shielding problems, however, results produced using these methods suffer from unphysical oscillations in scalar flux solutions that are a product of angular discretization. These aberrations are termed &ldquo;ray effects&rdquo;. </p><p> The Lagrange Discrete Ordinates (LDO) equations retain the formal structure of the traditional discrete ordinates formulation of the neutron transport equation and mitigate ray effects at high angular resolution. In this work, the LDO equations have been implemented in the Exnihilo parallel neutral particle radiation transport framework, with the deterministic scalar flux solutions passed to the Automated Variance Reduction Generator (ADVANTG) software and the resultant Monte Carlo variance reduction parameters&rsquo; efficacy assessed based on results from MCNP5. Studies were conducted in both the CADIS and FW-CADIS contexts, with the LDO equations&rsquo; variance reduction parameters seeing their best performance in the FW-CADIS method, especially for photon transport.</p><p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4797. Adviser: James F. Stubbins. Includes bibliographical references (leaves 164-171) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3243. Adviser: James F. Stubbins. Includes bibliographical references (leaves 230-240) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7075. Adviser: Robert S. Averback. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

<p> Developing new multifunctional materials in recent years for nuclear systems has become increasingly critical owing to the high demand on better shielding in extreme environments. The purpose of this research was to design, manufacture, and evaluate the feasibility of utilizing novel light weight close-cell composite metallic foam (CMF) and open-cell Al foam with fillers as radiation shields at nuclear facilities to attenuate the background of ionization radiations to a minimum level for creating a safer workplace, meeting regulatory requirements and maintaining high quality performance. </p><p> Steel-steel composite metal foams (S-S CMFs) and Aluminum-steel composite metal foams (Al-S CMFs) with various sphere sizes and matrix materials were manufactured and investigated for nuclear and radiation environments applications. 316L stainless steel, highspeed T15 steel and aluminum materials were used as the matrix material together with 2, 4 and 5.2 mm steel hollow spheres to manufacture various types of composite metal foams (CMFs). High-speed T15 steel is selected due to its high tungsten and vanadium concentration (both high-Z elements) to further improve the shielding efficiency of CMFs. This new type of S-S CMF is called High-Z steel-steel composite metal foam (HZ S-S CMF). Open-cell Al foams with fillers were obtained by infiltrating original empty pores with variety of hydrogen-rich compounds: petroleum wax, borated polyethylene, water, and borated water. </p><p> All the foams were investigated for their radiation shielding efficiency in terms of X ray, gamma ray and neutron. X-ray transmission measurements were carried out on a highresolution microcomputed tomography (microCT) system. Gamma-emitting sources: 3.0mCi ⁶⁰Co, 1.8mCi ¹³⁷Cs , 13.5mCi ¹²⁴Am, and 5.0mCi ¹³³Ba were used for gamma-ray attenuation analysis. The evaluations of neutron transmission measurements were conducted at the Neutron Powder Diffractometer beam facility at North Carolina State University. The experimental results were verified theoretically through XCOM and Monte Carlo Z-particle Transport Code (MCNP). </p><p> A mechanical investigation was performed by the means of quasi-static compressive testing. Thermal characterizations were carried out through effective thermal conductivity and thermal expansion analyses in terms of high temperature guarded-comparativelongitudinal heat flow technique and thermomechanical analyzer (TMA), respectively. The experimental results were compared with analytical results obtained from respectively Brailsford and Major&rsquo;s model and modified Turner&rsquo;s model for verification. Flame test was performed in accordance with United States Nuclear Regulatory Commission (USNRC) standard. CMF sample and a 304L stainless steel control sample were subjected to a fully engulfing fire with an average flame temperature of 800&deg;C for a period of 30 minutes. Finite Element Analysis was conducted to secure the credibility of the experimental results. </p><p> This research indicates the potential of utilizing the lightweight close-cell CMFs and open-cell Al foam with fillers as shielding material replacing current heavy structures with additional advantage of high-energy absorption and excellent thermal characteristics.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3760. Adviser: Roy Axford. Includes supplementary digital materials. Includes bibliographical references (leaves 260-263) Available on microfilm from Pro Quest Information and Learning.

<p> Boiling heat transfer is a powerful cooling mechanism used in a variety of industries to efficiently dissipate heat by taking advantage of latent heat. Nucleation site interactions have been demonstrated to affect behaviors in the bulk fluid, in the solid substrate and coalescence. Despite extensive studies of multi-site interactions, the conclusions of these studies are not in agreement. Namely, hydrodynamic effects are explained by some studies to promote nucleation while other studies find that, even with thermally isolated heat supplies, the presence of nearby sites diminishes nucleation. The present study identifies superheated fluid as a possible explanation for this variability. Hydrodynamic factors are determined to only promote single site nucleation if there is an appreciable thermal boundary layer present. Even with a thermal boundary layer, the presence of other sites causes competition over the superheated fluid; thus, diminishing the promotive effects of hydrodynamic factors. There have also been studies that have characterized the changing dimensions of the microlayer and the heat transfer that occurs beneath it. However, there is not a complete study of bubble behavior resulting from varying heater areas; specifically heater areas smaller than the microlayer. The present study quantifies the effect of heater diameter on vapor effectiveness and determines the optimal heater diameter. A metric for the coincidence of vapor production and microlayer coverage is proposed. Vapor effectiveness and the coincidence metric are shown to have similar relationships with heater diameter.</p><p>