A 40 kW transferred arc plasma melter was designed and built for the vitrification of nuclear waste. Borosilicate glass, high silica glass and sphene glass-ceramic were successfully melted with the waste using an argon plasma in both batch and continuous transferred arc plasma melters. / The use of both direct heating and indirect heating were examined in the continuous plasma melter. The loss of total glass weight and the elemental losses of Na, Cs, U and Nd were examined as a function of operating conditions. The losses of Cs during melting were from 25 to 73 wt% and depended on operating conditions. The loss of Cs during melting could be minimized by decreasing the plasma power, increasing the feed rate, using indirect heating rather than direct heating and choosing suitable waste form. / A heat transfer model and a mass transfer model were developed to analyze cesium losses during melting.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4797. Advisers: Barclay G. Jones; Ty A. Newell. Includes bibliographical references (leaves 135-144) Available on microfilm from Pro Quest Information and Learning.

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>

An experimental investigation of inverted annular film boiling heat transfer has been performed for vertical up-flow in a round tube. The working fluid was R-134a and the flow conditions covered a pressure range of 640 to 2390 kPa (water equivalent range: 4000 to 14000 kPa) and a mass flux range of 500 to 4000 kgm-2s-1 (water equivalent range: 700 to 5700 kgm-2s-1 ). The inlet qualities of the tests ranged from -0.75 to -0.03. The hot-patch technique is used to obtain the subcooled film boiling measurements. The parametric trends of the heat transfer coefficient with respect to mass flux, inlet quality, heat flux and pressure are examined and compared to reported parametric trends from the literature. The comparison shows agreement between observed effects of flow parameters with those reported by other researchers. The heat transfer vs. quality curve is divided into four different regions. It is shown that these regions are dependent on pressure, mass flux and local quality. A two-fluid one-dimensional model has been developed to predict the wall temperature of an internally-heated tube during IAFB. The model is derived using basic conservation equations of mass, momentum and energy. To simplify the derivation of the constitutive heat transfer relations, flow between two parallel plates is assumed. The model features shear stress and interfacial relations that make it accurately predicts the parametric effects and heat transfer characteristics of IAFB over a wide range of flow conditions. The model predicts wall temperatures of R-134a-cooled tubes with an average error of -1.21% and an RMS error of 6.37%. This corresponds to average and RMS errors in predicted heat transfer coefficients of 1.33% and 10.07%, respectively. Using water data, the model predicts wall temperatures with an average error of -1.76% and an RMS error of 7.78% which corresponds to average and RMS errors in predicted heat transfer coefficients of 4.16% and 15.06%, respectively.

No description available.

Master of Science / Department of Mechanical and Nuclear Engineering / William L. Dunn / One of the most pressing threats facing the United States is the increasingly effective use of improvised explosive devices or IEDs. Many commonly used techniques to detect explosives involve imaging. The primary drawback of imaging is that it requires interpretation of one or more images from each target. Human interpretation requires extensive training and is subject to the chance of false-negatives due to human fatigue. To counter the threat posed by IEDs, the signature-based radiation scanning (SBRS) technology has been developed. The goal of this project is to create an automated system, with minimal operator assistance, that is capable of detecting at least a gallon-sized explosive sample from at least one meter away. It is hoped that this can be accomplished quickly, in less than 30 seconds, with high sensitivity and specificity. The SBRS technique is based on the fact that many classes of materials have similar stoichiometries. For example, many common explosives have characteristic concentrations of hydrogen, carbon, nitrogen and oxygen. As neutrons interact with a material, unique gamma rays are created based on the composition of the material. Specifically, in this work, the gamma rays from inelastically scattered neutrons and from thermal neutron capture are investigated. Two neutron detectors are also used, whose responses depend on neutron thermalization in and around the target. Response templates are created based on gamma-ray and neutron responses that are collected from targets that contain explosives,. These templates are developed under different conditions for many different explosive materials to create a library of templates. The collection of responses from an unknown target is compared to a subset of the library of templates using a figure of merit to distinguish benign from explosive targets. Preliminary experiments were performed at Kansas State University. A high-purity germanium detector (HPGe) was used to detect the gamma rays. Two neutron detectors, one covered with cadmium, were used to detect back-streaming neutrons. A 252Cf radioisotope source as well as a Triga Mk III reactor were used as neutron sources.

The effect of non-catastrophic human body model positive electrostatic discharge pulses on the radiation response of low power VDMOS N-channel transistors is explored. The effect of multiple pulses of HBM ESD is to cause a change in threshold-voltage shifts between stressed and non-stressed devices when exposed to Co₆₀ gamma radiation. This difference is due to the build-up of a space charge region next to the Si/SiO₂ interface. This space charge region reduces the net electric field across the gate oxide when biased with a positive voltage and thus reduces the formation of holes and interface traps. Therefore, the ESD stressed devices appear to be less sensitive to radiation.

A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.

The long-term disposal of commercially generated high-level wastes (HLW) is of principal importance for the public safety because these wastes can be released to the environment and reach the biosphere. One solution for the isolation of the wastes is to put them into deep geologic repository. One way to predict the fate of the released radioactive species from deep geologic repository is to use a mathematical model. The mathematical model can be used to predict the transport in space and time of the radioactive species. Using as input parameters the characteristics for a specific place we can decide if a place can be used as a repository. We can cite here the "Yucca Mountain Site" in Nye County, Nevada, which is currently planned to be a HLW repository. We developed a three dimensional model of subsurface flow and reactive chemical transport. The second order partial differential equations governing the groundwater flow in saturated and unsaturated zones, and the advection-diffusion equation for the transport of solute are solved using the finite element method (FEM). The chemical phenomena are treated using the concept of point chemical equilibrium at each point of the mesh used in the finite element scheme. The Newton-Raphson method is employed to calculate the chemical equilibrium. The solute transport equation and the point chemical equilibrium are solved simultaneously using an iterative scheme. Radioactive decay is included in the solute transport equation and the chemical species phenomena of complexation, surface adsorption, ion-exchange, oxidation-reduction and precipitation are included in the point chemical equilibrium.