Browsing by Subject "Radiation"
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Item A revised model for radiation dosimetry in the human gastrointestinal tract(Texas A&M University, 2004-09-30) Bhuiyan, Md. Nasir UddinA new model for an adult human gastrointestinal tract (GIT) has been developed for use in internal dose estimations to the wall of the GIT and to the other organs and tissues of the body from radionuclides deposited in the lumenal contents of the five sections of the GIT. These sections were the esophagus, stomach, small intestine, upper large intestine, and the lower large intestine. The wall of each section was separated from its lumenal contents. Each wall was divided into many small regions so that the histologic and radiosensitive variations of the tissues across the wall could be distinguished. The characteristic parameters were determined based on the newest information available in the literature. Each of these sections except the stomach was subdivided into multiple subsections to include the spatiotemporal variations in the shape and characteristic parameters. This new GIT was integrated into an anthropomorphic phantom representing both an adult male and a larger-than-average adult female. The current phantom contains 14 different types of tissue. This phantom was coupled with the MCNP 4C Monte Carlo simulation package. The initial design and coding of the phantom and the Monte Carlo treatment employed in this study were validated using the results obtained by Cristy and Eckerman (1987). The code was used for calculating specific absorbed fractions (SAFs) in various organs and radiosensitive tissues from uniformly distributed sources of fifteen monoenergetic photons and electrons, 10 keV - 4 MeV, in the lumenal contents of the five sections of the GIT. The present studies showed that the average photon SAFs to the walls were significantly different from that to the radiosensitive cells (stem cells) for the energies below 50 keV. Above 50 keV, the photon SAFs were found to be almost constant across the walls. The electron SAF at the depth of the stem cells was a small fraction of the SAF routinely estimated at the contents-mucus interface. Electron studies showed that the ?self-dose? for the energies below 300 keV and the ?cross-dose? below 2 MeV were only from bremsstrahlung and fluorescent radiations at the depth of the stem cells and were not important.Item Detector Photon Response and Absorbed Dose and Their Applications to Rapid Triage Techniques(2009-05-15) Voss, Shannon PrenticeAs radiation specialists, one of our primary objectives in the Navy is protecting people and the environment from the effects of ionizing and non-ionizing radiation. Focusing on radiological dispersal devices (RDD) will provide increased personnel protection as well as optimize emergency response assets for the general public. An attack involving an RDD has been of particular concern because it is intended to spread contamination over a wide area and cause massive panic within the general population. A rapid method of triage will be necessary to segregate the unexposed and slightly exposed from those needing immediate medical treatment. Because of the aerosol dispersal of the radioactive material, inhalation of the radioactive material may be the primary exposure route. The primary radionuclides likely to be used in a RDD attack are Co-60, Cs-137, Ir-192, Sr-90 and Am-241. Through the use of a MAX phantom along with a few Simulink MATLAB programs, a good anthropomorphic phantom was created for use in MCNPX simulations that would provide organ doses from internally deposited radionuclides. Ludlum model 44-9 and 44-2 detectors were used to verify the simulated dose from the MCNPX code. Based on the results, acute dose rate limits were developed for emergency response personnel that would assist in patient triage.Item Development of mobile platform for inventory and inspection applications in nuclear environments(2015-12) Anderson, Robert Blake; Landsberger, Sheldon; Pryor, Mitchell WayneThe efforts made towards deploying a mobile robotic system at Los Alamos National Laboratory are detailed in this thesis. The platform application is non-contact tasks related to inspection, inventory, and radiation surveying. It is intended for a Special Nuclear Material storage facility featuring a high radiation environment and a variety of storage modes. New robotic capabilities have been developed using several mobile platforms to address the requirements of this application. Many of challenges are common to any warehouse application, such as autonomous task planning, vision, navigation, and inventory data management. Others are specific to a nuclear laboratory environment, such as radiation measurement and analysis, response to radioactive contamination, criticality safety, and restrictive security measures. This thesis describes the progress made towards meeting these challenges, outstanding issues, and future work that is necessary to complete the project. Nuclear facilities are under ever-increasing demands to reduce worker radiation exposure. Since the vault is a high radiation area, it is one of the first targets at Los Alamos for the application of novel solutions. The deployment of this system promises to enhance worker safety by reducing their presence inside the vault and therefore total occupational dose. As robotic systems become more trusted in the nuclear weapons complex, it also has the potential to reduce total operator labor by performing time-consuming tasks autonomously.Item Effect of HZE radiation and diets rich in fiber and n-3 poly unsaturated fatty acids (n-3 PUFA) on colon cancer in rats(Texas A&M University, 2006-08-16) Glagolenko, Anna AnatolievnaThis study examines the carcinogenic effect of HZE radiation and protective effects of different types of diets against colon carcinogenesis in a rat model. The effect of HZE radiation on health state and colon cancer development was evaluated. HZE radiation was found to suppress food consumption (P<0.0001) leading to lower body weight gain of irradiated rats when compared to the non-irradiated rats (P<0.05). The animals exposed to HZE radiation were found to start dying and/or getting pathologies 11 weeks earlier and at the end of the study had morbidity/mortality rate 14.2% higher (P=0.0005) than non-irradiated rats. There was no significant effect of HZE radiation on colon cancer incidence. The effects of dietary fibers and oils on health state and colon carcinogenesis were evaluated. Morbidity/mortality was found to be delayed in rats fed with pectinbased diets when compared to cellulose-based diet, regardless of radiation treatment. Similarly, fish oil was found to beneficially affect health of the experimental animals when compared to corn oil. Ten- and twenty-week delayed morbidity/mortality for irradiated and non-irradiated groups, respectively, was observed for rats fed with fish oil-based diets when compared to corn oil-based diets. Fish oil was also found to significantly reduce colon tumor incidence and multiplicity in non-irradiated rats (P<0.05). A similar trend was observed for the irradiated animals. No significant effect of fiber on colon cancer incidence was found. Finally, the effect of diets on general health and colon cancer development was investigated. Rats fed with corn oil/cellulose diet started dying and/or getting a disease earlier than rats fed with other diets, regardless of radiation treatment. The effect of diet on colon cancer development was found to depend on radiation treatment. Thus, in the absence of radiation treatment fish oil/cellulose was found to significantly reduce tumor incidence and multiplicity when compared to corn oil/pectin diet (P<0.05). In the presence of radiation treatment fish oil/pectin was found to lower the values of tumor incidence and tumor multiplicity, though the data obtained were not significant.Item Error analysis for radiation transport(2013-12) Tencer, John Thomas; Howell, John R.All relevant sources of error in the numerical solution of the radiative transport equation are considered. Common spatial discretization methods are discussed for completeness. The application of these methods to the radiative transport equation is not substantially different than for any other partial differential equation. Several of the most prevalent angular approximations within the heat transfer community are implemented and compared. Three model problems are proposed. The relative accuracy of each of the angular approximations is assessed for a range of optical thickness and scattering albedo. The model problems represent a range of application spaces. The quantified comparison of these approximations on the basis of accuracy over such a wide parameter space is one of the contributions of this work. The major original contribution of this work involves the treatment of errors associated with the energy-dependence of intensity. The full spectrum correlated-k distribution (FSK) method has received recent attention as being a good compromise between computational expense and accuracy. Two approaches are taken towards quantifying the error associated with the FSK method. The Multi-Source Full Spectrum k–Distribution (MSFSK) method makes use of the convenient property that the FSK method is exact for homogeneous media. It involves a line-by-line solution on a coarse grid and a number of k-distribution solutions on subdomains to effectively increase the grid resolution. This yields highly accurate solutions on fine grids and a known rate of convergence as the number of subdomains increases. The stochastic full spectrum k-distribution (SFSK) method is a more general approach to estimating the error in k-distribution solutions. The FSK method relies on a spectral reordering and scaling which greatly simplify the spectral dependence of the absorption coefficient. This reordering is not necessarily consistent across the entire domain which results in errors. The SFSK method involves treating the absorption line blackbody distribution function not as deterministic but rather as a stochastic process. The mean, covariance, and correlation structure are all fit empirically to data from a high resolution spectral database. The standard deviation of the heat flux prediction is found to be a good error estimator for the k-distribution method.Item G.R.A.C.E. satellite thermal model(2012-12) Jones, Fraser Black III; Howell, John R.I developed a thermal model of the Gravity Recovery and Climate Experiment satellite for the Center for Space Research to use in verifying their thermal models and for developing the next generation of satellites for their experiments. I chose COMSOL to model the satellite and used ProEngineer and 3Ds Max to generate the mesh from a .STEP file provided by DaimlerChrysler. I adjusted the model based on previous computer models and actual telemetry data from the GRACE satellite provided from 2002 through 2008. Using the model, I developed a sensitivity analysis of the satellites key thermal environment components and used that to recommend design changed for the next generation of satellites. Special attention should be given to redesigning the Star Camera Arrays and the heat transfer between the Main Equipment Platform and the Radiator.Item The k-distribution method for radiation heat transfer in non-isothermal real air-gas plasmas(2011-12) Tencer, John Thomas; Howell, John R.; Ezekoye, Ofodike A.The k-distribution method for treating the spectral properties of and absorbing-emitting medium represents an alternative to line-by-line calculations which reduces the number of evaluations of the radiative transport equation from the order of a million to the order of ten without any significant loss of accuracy. For problems where an appropriate reference temperature can be defined, the k-distribution method is formally exact and consists only of a change of variables in the spectral domain. However, when no appropriate reference temperature can be defined such as for strongly non-isothermal media, the method results in errors. These errors are difficult to quantify. There have been several attempts to implement corrections to the k-distribution method to extend its application to inhomogeneous media by modeling the effects of temperature, pressure, and concentration gradient. The Multi-Source Full Spectrum K-Distribution Method (MSFSK) introduced here extends the k-distribution method to non-isothermal media without variations in pressure or concentration. The MSFSK method manages to attain this goal by applying the superposition principle to the original RTE before applying the k-distribution transformation to decompose the problem into a set of sub-problems each of which is able to be solved effectively via the ordinary or modified full spectrum k-distribution method. The concept behind this new Multi-Source Full Spectrum K-Distribution Method is to break up the problem domain into isothermal or nearly isothermal emission zones. For each zone, the heat flux and flux divergence are calculated considering only emission from that zone. The RTE is solved using the full spectrum k-distribution method. The k-distribution for each gas volume is generated using the temperature of the current emission zone as the reference temperature. This process is repeated for each emission zone and the heat flux and flux divergence are summed. This method is applied to a variety of one dimensional slab geometry problems are results are presented. It is shown that the MSFSK method provides very accurate results for the radiative heat flux and flux divergence in these geometries. The effect of different quadrature schemes for performing the spectral integration on solution accuracy.Item Metamaterial window glass for adaptable energy efficiency(2014-05) Mann, Tyler Pearce; Ezekoye, Ofodike A.; Howell, John R.A computational analysis of a metamaterial window design is presented for the purpose of increasing the energy efficiency of buildings in seasonal or cold climates. Commercial low-emissivity windows use nanometer-scale Ag films to reflect infrared energy, while retaining most transmission of optical wavelengths for functionality. An opportunity exists to further increase efficiency through a variable emissivity implementation of Ag thin-film structures. 3-D finite-difference time-domain simulations predict non-linear absorption of near-infrared energy, providing the means to capture a substantial portion of solar energy during cold periods. The effect of various configuration parameters is quantified, with prediction of the net sustainability advantage. Metamaterial window glass technology can be realized as a modification to current, commercial low-emissivity windows through the application of nano-manufactured films, creating the opportunity for both new and after-market sustainable construction.Item Natural Convection and Radiation in Small Enclosures with a Non-Attached Obstruction(Texas A&M University, 2004-09-30) Lloyd, Jimmy LynnNumerical simulations were used to investigate natural convection and radiation interactions in small enclosures of both two and three-dimensional geometries. The objectives of the research were to (1) determine the relative importance of natural convection and radiation, and to (2) estimate the natural convection heat transfer coefficients. Models are generated using Gambit, while numerical computations were conducted using the CFD code FLUENT. Dimensions for the two-dimensional enclosure were a height of 2.54 cm (1 inch), and a width that varied between 5.08 cm and 10.16 cm (2 inches and 4 inches). The three-dimensional model had a depth of 5.08 cm (2 inches) with the same height and widths as the two-dimensional model. The obstruction is located at the centroid of the enclosure and is represented as a circle in the two-dimensional geometry and a cylinder in the three-dimensional geometry. Obstruction diameters varied between .51 cm and 1.52 cm (0.2 inches and 0.6 inches). Model parameters used in the investigation were average surface temperatures, net total heat flux, and net radiation heat flux. These parameters were used to define percent temperature differences, percent heat flux contributions, convective heat transfer coefficients, Nusselt numbers, and Rayleigh numbers. The Rayleigh numbers varied between 0.005 and 300, and the convective heat transfer coefficients ranged between 2 and 25 W/m2K depending on the point in the simulation. The simulations were conducted with temperatures ranging between 310 K and 1275 K on the right boundary. For right boundary temperatures above 800 K, the estimated error on the obstruction temperature is less than 6.1% for neglecting natural convection and conduction from the heat transfer analysis. Lower right boundary temperatures such as 310 K had significant contributions, over 50%, from heat transfer modes other than radiation. For lower right boundary temperatures, a means of including natural convection should be included. When a bulk fluid temperature and average surface temperature values are available, a time average heat transfer coefficient of 6.73 W/m2K is proposed for simplifying the numerical calculations. In the transient right boundary temperature analysis, all modes of heat transfer other than radiation can be neglected to have an error below 8.1%.Item Numerical Simulation of Three-Dimensional Combined Convective Radiative Heat Transfer in Rectangular Channels(2009-05-15) Ko, Min SeokThis dissertation presents a numerical simulation of three-dimensional flow and heat transfer in a channel with a backward-facing step. Flow was considered to be steady, incompressible, and laminar. The flow medium was treated to be radiatively participating. Governing momentum equations, energy equation, and the radiative equation were solved by a finite volume method. Extensive validation studies were carried out. As part of the validation study, three-dimensional combined convection and radiation in a rectangular channel without a backward-facing step was studied. The SIMPLE algorithm was used to link pressure and velocity fields. The combined convective-radiative heat transfer were studied by varying three parameters, i.e. optical thickness ( H ? =0.1, 0.2, and 0.4) and scattering albedo ( ?=0, 0.25, 0.5, 0.75 and 1). Variation of thermophysical properties with temperature was considered in this study. In this work consideration was given only to cooling. Effects of those radiative parameters on velocity, bulk temperature, and Nusselt number are presented in detail. The fluid with a hot inlet compared to a cold wall was cooled in a relatively short distance from the channel inlet because of the radiation effect. The thermal penetration decreased with a decrease in optical thickness and an increase in scattering albedo. Thermal penetration increased with increasing optical thickness and decreasing scattering albedo. The reattachment length varied with temperature due to variation of thermophysical properties with temperature.Item Substance of the sun : the cultural history of radium medicines in America(2010-08) Holmes, Robert Wendell, 1980-; Oshinsky, David M., 1944-; Hunt, Bruce J.; Kraut, Alan M.; Meikle, Jeffrey L.; Stoff, Michael B.From the moment Marie Curie announced the existence of radium, the strange new element captured the imagination of the American public. Radium, it seemed, could do anything. It gave off its own light and heat and appeared to realize the ancient alchemical dream of transmutation. It also showed promise as a medicine. The press ran with the idea that radium was a panacea that would cure everything from cancer to wife-beating. Soon it became impossible for the public to know what to believe when it came to radium and its effects on the body. Patent medicine companies exploited the murkiness surrounding ideas about radium, marketing a slew of products that claimed to harness the element’s healing and energizing powers. Meanwhile, physicians made slow, careful progress in defining the parameters of radium therapy, narrowing their focus to cancer. The popularity of radium patent medicines peaked in the 1920’s when hundreds of thousands of Americans purchased one or more of the dozens of radium products that proliferated at the time. Government regulators and members of the medical establishment sought to push these products from the market, but loopholes in the regulatory apparatus created under the Pure Food and Drug Act of 1906 allowed many of these companies to operate freely. Two scandals—the saga of the “Radium Girls” and the death of Eben Byers, a well-known industrialist who died after drinking over 1000 bottles of a radioactive tonic called Radithor—damaged radium’s image in the 1920’s and 1930’s. By the late 1930’s, strengthened regulatory laws helped push radioactive products from the marketplace. During World War II, scientists discovered artificial isotopes that proved more effective and less expensive than radium in the treatment of disease. For decades Americans had struggled to make sense of a scientific discovery that seemed to challenge fundamental ideas about the nature of the body and its relationship to the physical world. The ambiguities surrounding the element posed a unique challenge to progressive ideals of expertise and professionalization while providing a malleable image of energy and health that a variety of commercial interests could deploy.Item Temperature fluctuation analysis for GRACE twin satellites(2016-08) Fulcher, Ryan C.; Ezekoye, Ofodike A.; Bettadpur, Srinivas; Howell, John RThe overall objective of this research project is to find patterns and give a rudimentary explanation of these patterns in how heat flows through and around the GRACE Twin Satellites. Specifically, investigation of an unexplained frequency found in the temperature fluctuations gives rise to a new understanding of heat transfer in a complex mechanical system found in a near-vacuum environment. Impartial and unhindered information for this experiment come from two primary sources: the first is archived thermal analyses performed by the original manufacturers prior to the satellites’ launch in March 2002, and the second is current data feeds constantly streaming from the active satellites in orbit. The relevant data being extracted from this library of information for the purposes of this investigation are recorded at various time intervals, and taken from many locations, which are all discussed. These variables are used to run new simulations in attempt to recreate the original thermal analysis. Finally, significant changes in temperature leads to small thermal expansions, which can add noise to other data gathered by the satellites.Item The effects of radiation and extra-handling upon learning in the albino rat(Texas Tech University, 1961-05) Naylor, Lynda PearlNot available