Nuclear Engineering Commons^™

Development Of A Novel Framework For The Application Of Signature Based Safeguards (Sbs) To Pyroprocessing, Philip Leo Lafreniere

Nuclear Engineering ETDs

Traditional nuclear material accountancy (NMA) faces several challenges when applied to pyroprocessing facilities. To address these challenges, alternative methods of safeguarding nuclear material are being developed. One method is process monitoring (PM). PM involves taking operational process data and applying it to safeguards using an advanced framework. Signature Based Safeguards (SBS), a proposed PM framework, involves the identification of anomalous scenarios and the subsequent identification and detection of their respective PM signatures from a system of measurements. SBS has previously focused on failure modes that result in transfer of mass to unexpected places in the mass flowsheet. This work developed …

The Inverse Kinetics Method And Its Application To The Annular Core Research Reactor, Thomas A. Ball

Nuclear Engineering ETDs

The inverse kinetics method, is a method to calculate a reactor’s reactivity profile from its power profile. In this thesis, the reactivity profile corresponding to pulse operations of the Annular Core Research Reactor (ACRR) was sought. Of specific interest was the shutdown reactivity of the reactor following the pulse. This required accounting for delayed beryllium photoneutrons that are present in the ACRR in addition to U-235 delayed neutron precursors. The power profiles of the pulses were experimentally measured using a diamond photoconductive detector (PCD). Using the inverse kinetics equation, a computer code was written to numerically calculate the reactivity corresponding …

Evaluation Of Energy Released From Nuclear Criticality Excursions In Process Solutions, Corey Michael Skinner

Nuclear Engineering ETDs

Typically, the staff of a nonreactor nuclear facility or a processing facility involving nuclear material are not expected to have a strong technical background in nuclear criticality physics, as that is not the purpose of these sites, yet handle material with the potential to undergo a criticality excursion. Such excursions have occurred 22 times in the past, 21 of which involved an aqueous solution material. Therefore, it would be useful to have a general model capable of providing a quick estimation of the consequences of a criticality excursion in a processing plant. To this end, correlations developed utilizing experimental data …

Time-Of-Flight And Energy Loss Analysis On The Unm Fission Fragment Spectrometer, Shelby Fellows

Nuclear Engineering ETDs

The University of New Mexico spectrometer experimental work has been used to provide an event-by-event fission product measurement to aid in filling in the gaps in existing fission product yield data, as part of the Los Alamos National Lab Spectrometer for Ion Detection in Fission Research project (SPIDER) collaboration. This thesis examines the time-of-flight (TOF) component of the spectrometer towards improving the resolution of the system. Different thicknesses of TOF conversion foils were examined with alpha particles and fission fragments: 20, 55, and 100 µg/cm² carbon foils. For the thinnest carbon foil studied, a timing resolution of 160 ps …

Asymptotic Neutronic Solutions For Fast Burst Reactor Design, Edward L. Hobbs

Nuclear Engineering ETDs

Deterministic numerical methodologies for solving time-eigenvalue problems are valuable in characterizing the inherent rapid transient neutron behavior of a Fast Burst Reactor (FBR). New nonlinear solution techniques used to solve eigenvalue problems show great promise in modeling the neutronics of reactors. This research utilizes nonlinear solution techniques to solve for the dominant time-eigenvalue associated with the asymptotic (exponential) solution to the neutron diffusion and even-parity form of the neutron transport equation, and lays the foundation for coupling with other physics phenomena associated with FBRs.

High security costs and proliferation risks associated with Highly Enriched Uranium (HEU) fueled FBRs are the …

Time And Energy Characterization Of A Neutron Time Of Flight Detector Using A Novel Coincidence Method For Constraining Neutron Yield, Ion Temperature And Liner Density Measurements From Maglif Experiments, Jedediah Styron

Nuclear Engineering ETDs

The focus of this work is the characterization of a typical neutron time-of-flight (NTOF) detector that is fielded on inertial confinement fusion (ICF) experiments conducted at the Z-experimental facility with emphasis on the Magnetized Liner Fusion (MagLIF) concept. An NTOF detector consisting of EJ-228 scintillator and two independent photomultiplier tubes (PMTs), a Hamamatsu-mod 5 and Photek-PMT240, has been characterized in terms of the absolute time and energy response. The characterization was done by measuring single, neutron-induced events in the scintillator by measuring the alpha particle and neutron produced from the D-T reaction in kinematic coincidence. The results of these experiments …

Examination Of Color Center Formation In Caf2 Crystals When Exposed To Gamma And Mixed Neutron/Gamma Fields, Sara M. Pelka

Nuclear Engineering ETDs

Color centers in CaF₂ were studied in this work, in parallel with examinations of changes in the refractive index of the crystals by the larger research group, after they were subjected to radiation. Color centers induced by gamma rays and in mixed neutron-gamma fields were studied in CaF₂ and LiF using transmittance and absorbance spectra. The goals were to examine both neutron and neutron-gamma mixed field irradiations to be able to isolate neutron only effects and to correlate these color center effects with refractive index effects studied by our larger collaboration. Irradiation sources include ¹³⁷Cs, DD and …

High Precision Refractive Index Measurement Techniques Applied To The Analysis Of Neutron Damage And Effects In Caf2 Crystals, Joseph P. Morris Ph.D.

Nuclear Engineering ETDs

Neutron irradiation damages material by atomic displacements. The majority of these damage regions are microscopic and difficult to study, though they can cause a change in density and thus a change in refractive index in transparent materials. This work utilized CaF₂ crystals to track refractive index change based on neutron radiation dose. High precision refractive index measurements were performed utilizing a nested-cavity mode-locked laser where the CaF₂ crystal acted as a Fabry-Pérot Etalon (FPE). By comparing the repetition rate of the cavity and the repetition rate of the FPE, refractive index change was determined. Following several irradiation experiments, …

Experimental And Computational Investigations Of Heat Transfer Systems In Fluoride Salt-Cooled High-Temperature Reactors, Joel T. Hughes

Nuclear Engineering ETDs

Fluoride salt-cooled high-temperature reactors (FHRs) face a number of challenges similar to those faced by other Generation IV advanced reactor concepts. Predicting heat transfer in these systems accurately and reliably is one major challenge. Another is ensuring the safety of these systems during challenging operating conditions across the design basis envelope. Finally, achieving good economics to compete in a modern power generation portfolio is necessary for moving any nuclear power plant concept past the pre-conceptual stage. This dissertation attempts to support, from a thermal-hydraulics research standpoint, the case that the FHR can attain these goals. The dissertation focuses on several …

Remote Handled Disposal Enhancement At The Waste Isolation Pilot Plant, Philip Theisen

Nuclear Engineering ETDs

The Waste Isolation Pilot Plant (WIPP) is a deep underground facility for the disposal of Transuranic Defense Waste located in Southeastern New Mexico. Transuranic (TRU) Waste is defined as any radionuclides with an atomic number greater than that of Uranium, has a half-life greater than 20 years, and activity greater than 100nanocuries. According to the ‘Land Withdrawal Act’ (LWA), WIPP is licensed to dispose of 6.2million cubic feet of waste. TRU waste is categorized into two types: Contact Handled (CH) and Remote Handled (RH). CH waste is any waste that does not have a surface dose rate that exceeds 200mrem …

An Ionization Chamber For High Resolution Fission Product Spectroscopy, James Cole

Nuclear Engineering ETDs

The fission process has played a vital role in the world’s search for effective sources of alternative energy. With almost 80 years of work with fissionable material there is still much that is unknown about the process. Fission fragment mass and atomic number distributions are still lacking in completeness and critical detail. Knowledge of this information is highly sought after in the effort to improve various fields of nuclear physics and engineering such as reactor design, predictive models, waste disposal methods, and an overall understanding of the fission process. In an effort to better understand this process, we have developed …

Doppler Temperature Coefficient Calculations Using Adjoint-Weighted Tallies And Continuous-Energy Cross Sections In Mcnp6, Matthew A. Gonzales

Nuclear Engineering ETDs

The calculation of the thermal neutron Doppler temperature reactivity feedback co- efficient, a key parameter in the design and safe operation of advanced reactors, using first order perturbation theory in continuous energy Monte Carlo codes is challenging as the continuous energy adjoint flux is not readily available. Traditional approaches of obtaining the adjoint flux attempt to invert the random walk process as well as require data corresponding to all temperatures and their respective tem- perature derivatives within the system in order to accurately calculate the Doppler temperature feedback.

A new method has been developed using adjoint-weighted tallies and On-The-Fly (OTF) …

Fokker-Planck-Based Acceleration For Sn Equations With Highly Forward Peaked Scattering In Slab Geometry, Japan K. Patel

Nuclear Engineering ETDs

Short mean free paths are characteristic of charged particles. High energy charged particles often have highly forward peaked scattering cross sections. Transport problems involving such charged particles are also highly optically thick. When problems simultaneously have forward peaked scattering and high optical thickness, their solution, using standard iterative methods, becomes very inefficient. In this dissertation, we explore Fokker-Planck-based acceleration for solving such problems.

Advanced Stochastic Collocation Methods For Polynomial Chaos In Raven, Paul W. Talbot

Nuclear Engineering ETDs

As experiment complexity in fields such as nuclear engineering continually increases, so does the demand for robust computational methods to simulate them. In many simulations, input design parameters and intrinsic experiment properties are sources of uncertainty. Often small perturbations in uncertain parameters have significant impact on the experiment outcome. For instance, in nuclear fuel performance, small changes in fuel thermal conductivity can greatly affect maximum stress on the surrounding cladding. The difficulty quantifying input uncertainty impact in such systems has grown with the complexity of numerical models. Traditionally, uncertainty quantification has been approached using random sampling methods like Monte Carlo. …

Reduced-Order Monte Carlo Modeling Of Radiation Transport In Random Media, Aaron J. Olson

Nuclear Engineering ETDs

The ability to perform radiation transport computations in stochastic media is essential for predictive capabilities in applications such as weather modeling, radiation shielding involving non-homogeneous materials, atmospheric radiation transport computations, and transport in plasma-air structures. Due to the random nature of such media, it is often not clear how to model or otherwise compute on many forms of stochastic media. Several approaches to evaluation of transport quantities for some stochastic media exist, though such approaches often either yield considerable error or are quite computationally expensive. We model stochastic media using the Karhunen-Loève (KL) expansion, seek to improve efficiency through use …

Thin Film Alsb Carrier Transport Properties And Room Temperature Radiation Response, Erin Vaughan

Nuclear Engineering ETDs

Theoretical predictions for AlSb material properties have not been realized using bulk growth methods. This research was motivated by advances in molecular beam epitaxial (MBE) growth technology to produce high-quality thin-film AlSb for the purpose of evaluating transport properties and suitability for radiation detection. Simulations using MCNP5 were performed to benchmark an existing silicon surface barrier detector and to predict ideal AlSb detector behavior, with the finding that AlSb should have improved detection efficiency due to the larger atomic number of Sb compared with Si. GaSb diodes were fabricated by both homoepitaxial MBE and ion implantation methods in order to …

Innovative Open Air Brayton Combined Cycle Systems For The Next Generation Nuclear Power Plants, Bahman Zohuri

Nuclear Engineering ETDs

The purpose of this research was to model and analyze a nuclear heated multi-turbine power conversion system operating with atmospheric air as the working fluid. The air is heated by a molten salt, or liquid metal, to gas heat exchanger reaching a peak temperature of 660 0C. The effects of adding a recuperator or a bottoming steam cycle have been addressed. The calculated results are intended to identify paths for future work on the next generation nuclear power plant (GEN-IV). This document describes the proposed system in sufficient detail to communicate a good understanding of the overall system, its components, …

Stochastic Methods For Uncertainty Quantification In Radiation Transport, Erin D. Fichtl

Nuclear Engineering ETDs

The use of stochastic spectral expansions, specifically generalized polynomial chaos (gPC) and Karhunen-Loeve (KL) expansions, is investigated for uncertainty quantification in radiation transport. The gPC represents second-order random processes in terms of an expansion of orthogonal polynomials of random variables. The KL expansion is a Fourier-type expansion that represents a second-order random process with known covariance function in terms of a set of uncorrelated random variables and the eigenmodes of the covariance function. The flux and, in multiplying materials, the k-eigenvalue, which are the problem unknowns, are always expanded in a gPC expansion since their covariance functions are also unknown. …

Time Dependent Non-Extinction Probability For Fast Burst Reactors, Michael Gregson

Nuclear Engineering ETDs

Sandia National Laboratories has successfully operated fast burst reactors over the past four decades. Fast burst reactors refer to a type of reactor that is able to achieve intense neutron pulses in very short periods of time using fissile material. Typically these systems are comprised of enriched metallic uranium fuel. During operation of a fast burst reactor, a phenomena known as a pre-initiation has been known to take place. A pre-initiation occurs when the neutron population exceeds some fiducial prior to achieving the final reactivity state in a pulse operation. Reactivity is determined from the physical configuration of the reactor …

Brayton Rotating Unit Design And Analysis For Space Reactor Power Systems, Bruno Martin Gallo

Nuclear Engineering ETDs

This work developed designs and analyses models of centrifugal flow compressor and radial-inflow turbine of integrated Brayton Rotating Units (BRUs) for space reactor power systems. These models calculate the polytropic efficiency of the compressor and turbine, and the electric power and thermal efficiency of the BRUs and the power system for shaft rotational speed of 30 - 55 krpm, reactor power of 120 - 471 kW_th, turbine inlet temperatures of 900 - 1149 K, and He-Xe working fluids of 15 and 40 g/mole. The turbine and compressor models are coupled to the developed model of the rotating shaft …

Thermalhydraulics Analysis Of The Unit-Cell Nuclear Light Bulb Rocket Engine, Vojislav Banjac

Nuclear Engineering ETDs

This dissertation presents a detailed thermalhydraulics analysis of the unit-cell derivative of the Nuclear Light Bulb (NLB) rocket engine. The NLB engine is a gas core nuclear rocket first proposed in the 1960's by the then-United Aircraft Research Laboratories (UARL); its unit-cell derivative consists of a low-temperature moderator/reflector as well as segmented propellant channels, both proposed with the intent of increasing the k_eff of the system.

The results of this work can be grouped into two major areas: (1) thermal and neutronics analysis of the engine, and (2) investigation of the feasibility of the engine over a wide range …

Impact Of Nuclear Rocket Engine Design On Control Strategies, John A. Lambright

Nuclear Engineering ETDs

In a nuclear thermal rocket engine, the propellant gas can be varied independent of the peak chamber temperature. Startup and shutdown times can be varied over a wide range due to this uncoupling of the energy source from the working fluid. Therefore, in the early stages of nuclear rocket engine development. a study of the impact of the engine design on control strategies and systems was conducted. In order to define what is required in terms of engine thrusting times. this study focused on the thrust requirements for a Reusable Orbital Transfer Vehicle (R0TV).

Three nuclear rocket designs were used …

Agglomarate Formation During Drying Of Fine Powders, Alok Maskara

Nuclear Engineering ETDs

The effect of capillary pressure, solubility, and surface chemistry on agglomeration of silica and titania particles during drying was studied. Three batches of silica particles with diameter between 15 and 500 nm as well as titania particles with nominal diameter of 30 nm were used. Drying rate was varied by using both tray drying and spray drying. Aprotic solvents ranging in surface tension from 18 dynes/cm (hexane) to 72 dynes/cm (water), and mixtures of water/propanol and water/butanol ranging in surface tension from 35 dynes/cm to 72 dynes/cm, were used to vary the surface tension of the solvent. Water between pH …

Conceptual Design Of The Modular Transuranic Shipping Cask Mts-54, Vojislav Banjac

Nuclear Engineering ETDs

The storage, transportation, and disposal of radioactive waste has become a problem of immense proportions in the United States. This Thesis focuses on the transportation of defense transuranic (TRU) waste to the Waste Isolation Pilot Plant (WIPP) repository near Carlsbad, New Mexico. The objective of the cask conceptual design was based on the following:

• Taking into account the latest available data on TRU waste drum mass, investigate the possibility of increased drum capacity per shipment over the current design;
• Present a new TRU cask design with increased drum capacity and the potential for transporting both Contact-handled (CH and Remote-handled (RH) …

Coupled Radiation Transport / Thermal Analysis Of The Radiation Shield For A Space Nuclear Retractor, William John Barattino

Nuclear Engineering ETDs

The renewed interest of conducting operations in space has given rise to re-establishment of space reactor systems development. The current SP-100 program is focussing on design of a 100 kW nuclear e reactor for space application. This research project investigated the coupling between radiation transport, energy deposition, and temperature distribution for a variety of space reactor shield configurations. The basic shield design consisted of tungsten [W], and natural lithium hydride either cast or pressed into a stainless steel matrix [LiH(Nat)].

For a nuclear reactor operating at a power level of 1.66 MW_th, temperature feedback effects on energy deposition …

Film Boiling Destabilization From Hydrodynamic And Thermodynamic Considerations, Fred Samuel Gunnerson

Nuclear Engineering ETDs

An analytical method is presented for predicting, from first principles, the minimum heater temperature and heat transfer rate at the onset of film boiling for spherical and ·flat plate heaters in saturated and subcooled liquids. Within the analysis, consideration is given to the two types of film boiling, they are:

(1) Pool film boiling where the entire heater is submerged within the boiling liquid, and

(2) Leidenfrost film boiling where a droplet of liquid boil s above a horizontal plate heater.

The Effect Of Volatile Fission Products On Fuel Motion In Nuclear Fuel Elements, Paul Sasa

Nuclear Engineering ETDs

Stringent licensing procedures for commercial nuclear reactor operation require an in-depth analysis of the phenomena associated with postulated reactor core overheating accidents. One aspect of nuclear reactor safety assessment is a prediction of fuel behavior associated with such postulated overheating events, which includes an assessment of the role of fission product inventory contained within irradiated fuel elements on fuel relocation potential. In general the gaseous fission product, such as Xenon and Krypton, have been considered the most likely candidates for fuel relocation due to gas dissolution from the fuel matrix and bubble expansion during fuel overheating; thus, such gaseous fission …

A System For Detecting Neutrons In The Harsh Radiation Environment Of A Relativistic Electron Beam, Lyle Wayne Kruse

Nuclear Engineering ETDs

Newly developed detectors and procedures allow measurement of neutron yield and energy in the harsh radiation environment of a relativistic electron beam source. A new photomultiplier tube design and special gating methods provide the basis for novel time-of-flight and total-yield detectors. The technique of activation analysis is expanded to provide a neutron energy spectrometer. There is a demonstrated potential in the use of the integrated system as a valuable diagnostic tool to study particle-beam fusion, intense ion-beam interactions, and pulsed neutron sources for simulating weapons effects. A physical lower limit of 10⁸ neutrons into 4π is established for accurate …

Improvement To The Solution Of Stefan-Like Freezing And Melting Problems, With Application To Lmfbr Safety Analysis, Mohamed Shafik El-Genk

Nuclear Engineering ETDs

This work involves development of improvements to two analytical methods to predict the instantaneous position of the moving phase-change front in one-dimensional Stefan-like problems. These techniques, the refined integral heat balance and the upper and lower bounds averaging methods, are useful in practical applications for reactor safety analysis, under hypothesized conditions leading to molten fuel relocation problems. With such applications in mind, the two methods are applied to four different one-dimensional problems which involve change-of­phase, with or without a convective boundary condition at the moving front. Comparison with the exact solution has been presented whenever possible; ultimately, all solutions have …

Vacuum-Freezing Vapor-Desublimation High Pressure Ice-Melting Process For Water Desalination, Ting-Chuan Chung

Nuclear Engineering ETDs

The present thesis study makes a preliminary technical feasibility study and a preliminary economic study of the Vacuum-Freezing Vapor-Desublimation High Pressure Ice-melting Process that was first introduced by C. Y. Cheng and W. Cheng. In the study, the processing steps are divided up into several key unit operations. Some of these key unit operations are similar to some operations in existing vacuum freezing processes and have already been studied extensively. Some key operations are, however, unique to the process under study. The feasibility study is made by borrowing information for the unit operations that have already been studied in connection …