Engineering Commons^™

Radiation Effects On Metastable States Of Superheated Water, Charles William Alvord

Doctoral Dissertations

Radiation Effects on Metastable States of Superheated Water covers theory, application, and experimentation into the behavior of water at temperatures above the boiling point. The backgrounds of Positron Emission Tomography target design, bubble chambers, and superheat measurements are presented. The quantitative theory of metastable liquids and their characteristic waiting time is discussed. Energetics of bubble formation from two different perspectives are included. Finally, the design of an apparatus for measuring liquid superheats in the presence of radiation is covered in some detail, including several design iterations, first measurements made on the apparatus, and techniques for data reduction.

Optimal Designs Of Mobile Nuclear Engines To Power Manned Vehicles On Mars, Robert D. Woolley

Masters Theses

This work develops original conceptual designs for compact nuclear fission reactor engines to power robust mobile equipment operating on the surface of the planet Mars. This is a nuclear application area not well explored in previous publications. Some novel analytical approaches are developed herein, including the application of optimal control theory to minimize radiation shielding mass. This work also provides the first study of using another planet's atmosphere to implement open-cycle thermal conversion systems.

To power equipment on Mars for extended durations at sustained power levels ranging from one hundred horsepower to several thousand horsepower, there is no practical alternative …

Dose Modeling And Statistical Assessment Of Hot Spots For Decommissioning Applications, Eric Warner Abelquist

Doctoral Dissertations

A primary goal of this research was to develop a technically defensible approach for modeling the receptor dose due to smaller "hot spots" of residual radioactivity. Nearly 700 combinations of environmental pathways, radionuclides and hot spot sizes were evaluated in this work. The hot spot sizes studied ranged from 0.01 m² to 10 m², and included both building and land area exposure pathways. Dose modeling codes RESRAD, RESRAD-BUILD, and MicroShield were used to assess hot spot doses and develop pathway-specific area factors for eleven radionuclides. These area factors are proposed for use within the existing Multiagency Radiation …

An Improved Knockout-Ablation-Coalescence Model For Prediction Of Secondary Neutron And Light-Ion Production In Cosmic Ray Interactions, Sirikul Sriprisan

Doctoral Dissertations

An analytical knockout-ablation-coalescence model capable of making quantitative predictions of the neutron and light-ion spectra from high-energy nucleon-nucleus and nucleus-nucleus collisions is being developed for use in space radiation protection studies. The FORTRAN computer code that implements this model is called UBERNSPEC. The knockout or abrasion stage of the model is based on Glauber multiple scattering theory. The ablation part of the model uses the classical evaporation model of Weisskopf-Ewing. In earlier work, the knockout-ablation model was extended to incorporate important coalescence effects into the formalism. Recently, the coalescence model was reformulated in UBERNSPEC and alpha coalescence incorporated. In addition, …

A Methodology For Establishing Zones Of Acceptable Caas Coverage For A New Storage Facility Utilizing Mcnp 5 In Adjoint, Zia A. Tompkins

Masters Theses

ANSI/ANS 8.3 “Criticality Accident Alarm System”, Appendix B states “Determining the adequacy of criticality alarm detector placement is far from an exact process”. With this statement in mind a novel method for establishing areas of acceptable Criticality Accident Alarm System (CAAS) coverage was developed and demonstrated utilizing Los Alamos’ Monte Carlo N-Particle Code 5 (MCNP5) in multigroup Adjoint. Validation of the methodology was shown in the comparison of benchmark calculations with empirical results of Sandia testing and with hand calculations utilizing ANS 8.3. Demonstration involved the determination of zones of CAAS coverage from detector sensitivity maps generated by MCNP5 for …

The Solubility And Diffusivity Of Helium In Mercury With Respect To Applications At The Spallation Neutron Source, Matthew W. Francis

Doctoral Dissertations

Models for solubility of noble gases in liquid metals are reviewed in detail and evaluated for the combination of mercury and helium for applications at the Spallation Nuetron Source (SNS) at Oak Ridge National Laboratory (ORNL). Gas solubility in mercury is acknowledged to be very low; therefore, mercury has been used in ASTM standard methods as a blocking media for gas solubility studies in organic fluids and water. Models from physical chemistry predict a Henry coefficient for helium in mercury near 3.9x10¹⁵ Pa-molHg/molHe, but the models have large uncertainties and are not verified with data. An experiment is designed …