Mountain Scholar :: Browsing by Author "Johnson, Thomas, committee member"

Browsing by Author "Johnson, Thomas, committee member"

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Open Access
A comparison of air samples at ground level and aerial gamma count rates from the response to the Fukushima Dai-Ichi Nuclear Power Plant accident
(Colorado State University. Libraries, 2014) Sublett, Sarah Miriam, author; Brandl, Alexander, advisor; Biedron, Sandra, committee member; Johnson, Thomas, committee member
March 11, 2011 will be a day that will never be forgotten in the minds of the thousands of Japanese people whose lives were forever changed by a series of natural disasters, including a 9.0 earthquake and subsequent tsunami that triggered the Fukushima Dai-Ichi Nuclear Power Plant (FDNPP), located on the eastern coast of Japan, to become cripplingly damaged. The FDNPP nuclear accident resulted in the emission of radionuclides into the environment and those released nuclides, specifically 134Cs, 137Cs, and 131I and their measurement by ground and air based means, are the subject of this research project. Within the first few days following the start of the disaster, numerous US federal agencies responded and deployed to Japan to help characterize and measure the release of radionuclides from FDNPP. Over the course of approximately a two-month span, over 500,000 measurements were obtained and analyzed, including air and soil samples and in situ spectra. The core of this research project was to analyze and compare ground air samples to aerial gamma count rate measurements obtained in Fukushima Prefecture within the first two months following the disaster. The results of this project estimate the ground deposition of radionuclides in Fukushima Prefecture, which accounted for 99.4% of the measured aerial net gamma count rate. Another finding of this project is the estimated ground deposition of nuclides based upon aerial gamma count rates in areas where there was measurable ground air contamination was 14.25 times higher than in areas where there was no measurable ground air contamination as determined by the evaluated air samples in this project. Of the samples evaluated in this project, ground deposition averaged 5.4E6 Bq/m2 in areas where there was measurable ground air contamination, versus 3.79E5 Bq/m2 in areas where there was no measurable ground air contamination.
Open Access
An ultra-high resolution pulsed-wire magnet measurement system
(Colorado State University. Libraries, 2016) D'Audney, Alex, author; Milton, Stephen, advisor; Biedron, Sandra, advisor; Johnson, Thomas, committee member
The performance of a Free-Electron Laser (FEL) depends in part on the quality of the magnetic field in the undulator. Ideally the magnetic field on the axis of the undulator is transverse to the axis and sinusoidally varying due to the periodic sequence of alternating field dipole magnets. The resulting ideal trajectory of a relativistic electron bunch traveling along the axis is also sinusoidal in the plane perpendicular to that of the ideal magnetic field. Imperfections in the magnetic field lead to an imperfect electron trajectory, both offset and angle, as well as a relative phase error between the oscillation phase of the electrons and the generated electromagnetic field. The result of such errors is a reduction of laser gain impacting overall FEL performance. A pulsed-wire method can be used to determine the profile of the magnetic field. This is achieved by sending a square-current pulse through a wire placed along the length of the axis that will induce an Lorentz-force interaction with the magnetic field. Measurement of the resulting displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field and so provides a measure of the local magnetic field strength. Dispersion in the wire can be corrected using algorithms, with a resulting increase in overall accuracy of the measurement. Once the fields are known, magnetic shims can be placed to correct the magnetic fields to the desired level. In this thesis we will describe the design, construction and testing of a pulsed-wire magnetic measurement system and use this system to characterize the CSU FEL undulator.
Open Access
Characterization of X-ray transmission and scattering during equine radiology procedures at the Johnson Family Equine Hospital
(Colorado State University. Libraries, 2023) Parajuli, Bal K., author; Brandl, Alexandar, advisor; Johnson, Thomas, committee member; Lindsay, James, committee member
Personnel handling radioactive materials or radiation-emitting devices are at risk of exposure to ionizing radiation, directly from primary beams and indirectly from scattered beams. Hence, radiation workers are enrolled in a radiation dosimetry program to comply with regulations and effectively track exposures. Because X-ray radiation is used daily for diagnostics and therapeutics of animals at the Veterinary Teaching Hospital (VTH) of the Colorado State University (CSU), the Radiation Control Office (RCO) at CSU monitors the workers' radiation dose monthly to ensure safety and compliance. The RCO has set an ALARA Level 1 investigation at 150 millirems (mrem) in a month to keep doses As Low As Reasonably Achievable (ALARA). Personnel exceeding 150 mrem in a month are notified, and the dose is investigated. An investigation level of 150 mrem provides an opportunity for the RCO to intervene early and is low compared to the regulatory annual dose limit of 5000 mrem per year. Over the course of the last few years, the ALARA Level 1 has been exceeded on various occasions by radiology technicians at the Johnson Family Equine Hospital (JFEH), which is affiliated with the VTH at CSU. This project was designed to bridge a substantial knowledge gap regarding the procedures conducted at the JFEH, associated radiation doses, and the facility's suitability for large-animal veterinary applications. This experiment design characterizes the facility and anticipates radiation exposures across various spatial points within the radiology areas, facilitating the identification of radiation exposure hotspots. This study started with staff interview, comprehensive analysis of the daily diagnostic imaging procedures at the JFEH and cross-referencing months with elevated exposure to images. Radiation exposures in the primary beam were modelled for all Technique Factors (TFs) at various distances using SpekCalc® software generated photon fluence energy spectra. The output spectrum data were entered into an MCNP® model for dose assessment using effective dose conversion coefficients. The benchmarked outcome for Cesium-137 differed 3% from the theoretical value. An MCNP® model was used to replicate the direct measurements conducted at 1 meter. The results were consistent with exposure measured by a Biomedical Fluke 451P ionization chamber, previously published exposure measurement for the given kVp and mAs, the calculated exposure for X-ray using kVp and mAs, and the typical effective radiation dose from diagnostic X-ray published by NCRP 160. Finally, another simulation was conducted to recreate the conditions within the radiology facility using phantoms. This simulation facilitated the quantification of effective doses across various spatial points. The simulated absorbed dose was highest in the primary beam, then directly behind the X-ray source, and lowest at a 90-degree angle from the direction of the beam, at the same distance from the source. The absorbed dose also differed considerably in front of and behind the phantom due to photoelectric absorption. After analyzing data, to measure dose accurately, two dosimeters are recommended, one inside and one outside the lead vest. Absorbed dose can be minimized by avoiding primary beam exposure and standing behind the X-ray tube while operating the handheld X-ray switch.
Open Access
Decontaminating cobalt-60 from wounds
(Colorado State University. Libraries, 2013) Mannis, Daniel, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Lindsay, James, committee member
Removing radionuclide contamination from wounds in tissue is essential to minimizing incorporation and dose to an individual. This experiment compared the effectiveness of decontaminating wounds inflicted in pig tissue that were contaminated with cobalt-60. The process was established to compare three decontamination methods consisting of: commercially available, non-prescription, surfactant based, non-ionic wound cleanser spray; physiologic saline solution spray; physiologic saline solution pour. Three wound types were used: smooth incision, jagged cut, and blunt force trauma wounds. The cleanser spray and the saline spray were more effective at decontaminating all three wounds than the saline pour. The difference between the cleanser spray and saline spray was not statistically significant, but the cleanser spray did decontaminate the wound to a lower mean value. The spray pressure used for the saline and cleanser sprays produced the most noticeable impact in the decontamination process.
Open Access
Design and simulation of the Colorado State University linear accelerator system
(Colorado State University. Libraries, 2014) Edelen, Jonathan Paul, author; Milton, Stephen, advisor; Biedron, Sandra, advisor; Notaros, Branislav, committee member; Johnson, Thomas, committee member
The University of Twente in the Netherlands recently donated a linear accelerator and free-electron laser system to Colorado State University. A detailed model and simulation of the system must be constructed in order to assist the re-commissioning process at CSU. An initial design of the beam-transport system must also be developed. This thesis begins with the basic theory needed to understand the context of the simulations and then works through the accelerator, starting from the point where the beam is generated and continuing through the whole system to the beam dump. Individual components are simulated, their parameters are characterized, and optimal initial settings are found. These individual simulations are then combined into a complete start-to-end simulation of the machine. The start-to-end simulation is then used to demonstrate the expected performance of the machine with the optimal settings. This provides a system design that will be used in the initial buildup of the accelerator, as well as a simulation tool that can be used for future studies (for example, testing of novel components) or for examining the impact of proposed design changes.
Open Access
Designing novel radio-frequency coils for high field and ultra-high field magnetic resonance imaging
(Colorado State University. Libraries, 2021) Athalye, Pranav Shrikant, author; Notaroš, Branislav, advisor; Ilić, Milan, committee member; Pezeshki, Ali, committee member; Johnson, Thomas, committee member
High field and ultra-high field magnetic resonance imaging is the upcoming technology in the field of magnetic resonance imaging. This has created the need for designing of new radio frequency (RF) coils. Here are presented several of these novel RF coils include multifilar helical antenna coils for 3-T, 4.7-T, 7-T and 10.5-T NMR scanners, slotted-waveguide array coils for 7-T, inverted microstrip array coil for 7-T along with other methods to improve the efficiency and homogeneity of the RF field. The coils were simulated using commercial electromagnetic solvers including WIPL-D and ANSYS-HFSS, and some were also measured experimentally. The results for B1+ efficiency are compared with state-of-art coils. These novel coils exhibit high B1+ efficiency, strong right-hand polarization, good field homogeneity with an acceptable level of SAR. Details of numerical methods for the simulations of the coils has also been discussed. Ongoing work and future plans have also been presented.
Open Access
Dose profile surrounding a waste repository
(Colorado State University. Libraries, 2014) Parson, Jenelle, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Woody, Robert, committee member
The waste repository analyzed is an interim storage facility that houses low and intermediate level conditioned radioactive waste. In total, it contains 9996 200-L waste barrels. The barrels are arranged in a crate geometry to ensure easy access to each barrel. The repository walls are 0.2 m thick with extra shielding (0.7 m) present on the west, north, and east sides of the repository. Instead of extra shielding the south side of the repository has a 5.25 m gap from the crates to the wall, allowing for crane maneuverability. The dose rate profile was analyzed using Monte Carlo N-Particle Transport eXtended (MCNPX) for the south, west, and north sides. The east side was not explicitly analyzed, because of the symmetry between the west and east sides. The dose rate was analyzed using f5 detector tallies and fluence rate to dose rate conversion factors from ICRP 21. Here, contributions due to skyshine and other wall effects are analyzed in detail. For the west and north side (where shielding was present), it was found that as distance from the source increases the dose rate initially increases logarithmically to a maximum and subsequently falls off following an exponential function. The initial increase in dose rate is significant with a peak dose rate as much as 300% of the dose rate at the wall and remaining elevated until approximately 60 m from the waste repository. A similar dose rate increase is not observed for the southern side of the repository; instead, the dose rate falls off with a power function corresponding to a function between that for an infinite plane and a point source. The dose rate profile was analyzed with and without repository structures, and the initial increase is only present with the repository structure. This indicates that the initial rise is due to the presence of walls and/or roof. The shape of the dose rate profile closely follows observed skyshine functions at accelerator facilities. Skyshine and wall effects have been analyzed extensively for medical accelerator facilities, but are generally not considered for a waste repository; the work suggests that skyshine and wall effects may be more significant than previously thought and should be considered in the design and construction of waste repositories.
Open Access
Effect of matrix constituents on the determination of plutonium and americium in bone
(Colorado State University. Libraries, 2019) Nguyen, Nhung Thi Nho, author; Sudowe, Ralf, advisor; Johnson, Thomas, committee member; Borch, Thomas, committee member
There are numerous methods available in the literature for separating and analyzing radionuclides of interest from an array of environmental matrices. The quality of these methods can be affected by the stable elements that are commonly found in many of these samples. The presence of such interfering constituents can result in incomplete separation of the radioisotopes of interest as well as a reduced rate of recovery. This is especially the case when complex matrices such as samples of bone and bone ash are analyzed. Plutonium and americium tend to concentrate in bone, they are therefore often referred to as bone seekers. They accumulate in actively metabolizing portions of bones of mammals including humans. It is therefore extremely important to study and evaluate the accumulation of these radionuclides in human bone by analyzing bone samples. However, calcium, which is present in high concentrations in the hydroxyapatite that constitutes the bone, as well as sodium and potassium, have the potential to strongly affect the efficacy of radiochemical separation methods. The objective of this research is to investigate the influence of the major and minor elemental constituents present in bone on the affinity of plutonium and americium for a variety of commercial extraction chromatographic resins.
Open Access
Effects of pH, temperature and competing ions on the adsorption of radiocesium on Prussian blue coated detonation nanodiamonds from aqueous solutions
(Colorado State University. Libraries, 2024) Zaiger, Megan, author; Sudowe, Ralf, advisor; Johnson, Thomas, committee member; Lindsay, James, committee member
The accident at the Fukushima Nuclear Powerplant, in 2011, resulted in the generation of radioactive contaminated water which is currently being stored on site. The Tokyo Electric Power Company (TEPCO), who owns the powerplant has begun treating and releasing the water into the ocean after most of the radioactivity has been removed by the Advanced Liquid Processing System (ALPS). Current techniques for preconcentration of radioisotopes, particularly radiocesium, from ocean waters are very labor and time intensive and often take months. Therefore, efficient, rapid, and reliable methods are needed for the determination of radiocesium in ocean water which represents a critical gap that this work seeks to address. A new technique using Prussian Blue (PB) coated detonation nanodiamonds (DND) to adsorb radiocesium from water samples is being investigated by the research group. The new technique takes hours to preconcentrate the radiocesium instead of months. The current study focuses on the effects of varying pH, temperature, competing ions, and stable cesium (Cs) on adsorption behavior of radiocesium. The results of the study show that high pH will result in a minimal decrease in Cs adsorption, while adsorption increases as pH increases, with the lowest adsorption of 95%. Temperature changes resulted in minimal decreases in Cs adsorption with the lowest adsorption of 98% measured at 4°C. Presence of potassium chloride (KCl), sodium chloride (NaCl), and lithium chloride (LiCl) at concentrations up to 1.0 M had no effect on the uptake of radiocesium showing adsorption of above 97% for all elements. However, adsorption decreased significantly in the presence of rubidium chloride (RbCl) as interferent concentration increased, with the lowest adsorption of 68% recorded for 1.0 M RbCl. The addition of stable Cs to low amounts of Cs-137 (1 Bq) saw high uncertainties and low adsorption reflecting the difficulty to obtain consistent results at very low concentrations. The study has shown promise for the use of DND in environmental settings with a continued need to be able to detect low levels of Cs-137.
Open Access
Efficiency modeling for neutron detectors
(Colorado State University. Libraries, 2014) Scallan, Lisa Marie, author; Brandl, Alex, advisor; Johnson, Thomas, committee member; Chen, Suren, committee member
Neutron detectors are used for various applications, such as for workplace monitoring in a neutron field, during nuclear incidents, and for the detection of contraband nuclear material. The Remote Sensing Laboratory has developed and employed several neutron detector designs, and characterization data have been collected with these detectors under varying environmental conditions. Using MCNP/MCNPX the neutron fluence rate and dose rate were evaluated during open-field deployment as a function of moisture content in air and soil, barometric pressure, and varying pavement and soil composition. The focus of this analysis was on the incident neutron spectra, detector efficiency and count rate at the detector location. The most prevalent parameters directly contributing to scattered neutrons into the active detector volume were evaluated. Experimentally observed functional dependence on the source-detector distance was compared to MCNP/MCNPX simulation data. This study provides detector efficiency data for a wide range of operational conditions beyond the current capacity for experimental detector characterization.
Open Access
Evaluation of sodium bismuthate chromatographic systems for the separation of americium from curium
(Colorado State University. Libraries, 2023) Labb, Samantha A., author; Sudowe, Ralf, advisor; Brandl, Alexander, committee member; Johnson, Thomas, committee member; Henry, Charles, committee member
The development of a successful and efficient americium (Am) and curium (Cm) separation method is necessary for stockpile stewardship science and for the simplification and improvement of currently proposed reprocessing schemes towards the closure of the nuclear fuel cycle. However, the similar chemical properties of these radionuclides (e.g., similar ionic radii, ionic bonding, and predominant trivalent oxidation states in acidic media) makes this difficult to achieve. Differences in redox chemistry can be exploited based on the fact that Am can be oxidized to higher oxidation states in acidic media while Cm cannot. Recently, the ability of solid sodium bismuthate to oxidize Am and its ion exchange properties were demonstrated in solvent extraction and chromatographic systems, but were limited by oxidation stability, kinetics, and flow rates. This dissertation focuses on evaluating and characterizing new solid-liquid chromatographic systems that combine both the oxidation and ion exchange mechanisms into one material for a continuous separation process. In addition, the solution behavior of NaBiO3 in nitric acid and the effect on acidity and dissolution kinetics is determined.
Open Access
Improved detection of radioactive material using a series of measurements
(Colorado State University. Libraries, 2016) Mann, Jenelle, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Kokoszka, Piotr, committee member; Leary, Del, committee member
The goal of this project is to develop improved algorithms for detection of radioactive sources that have low signal compared to background. The detection of low signal sources is of interest in national security applications where the source may have weak ionizing radiation emissions, is heavily shielded, or the counting time is short (such as portal monitoring). Traditionally to distinguish signal from background the decision threshold (y*) is calculated by taking a long background count and limiting the false negative error (α error) to 5%. Some problems with this method include: background is constantly changing due to natural environmental fluctuations and large amounts of data are being taken as the detector continuously scans that are not utilized. Rather than looking at a single measurement, this work investigates looking at a series of N measurements and develops an appropriate decision threshold for exceeding the decision threshold n times in a series of N. This methodology is investigated for a rectangular, triangular, sinusoidal, Poisson, and Gaussian distribution.
Open Access
Investigation of the bioavailability of radiocesium in the Fukushima exclusion zone using a sequential extraction technique
(Colorado State University. Libraries, 2019) McNabb, Ian, author; Sudowe, Ralf, advisor; Johnson, Thomas, committee member; Borch, Thomas, committee member
The nuclear reactor accident at the Fukushima Daiichi power plant in March of 2011, resulted in the release of large quantities of various radionuclides into the environment. The main radionuclide of concern still remaining today is cesium-137 due to its 30-year half-life. Several areas in the vicinity of the power plant are still considered an exclusion zone owing to contamination with radiocesium, and they have not been cleared for human resettlement. While these parts are not suitable for permanent habitation, they are accessible for field work. The purpose of this research was to analyze the movement and bioavailability of radiocesium in the ecosystems contaminated by fallout from the Fukushima Daiichi nuclear reactor accident. This was achieved by analyzing soil cores collected from within the exclusion zone. The core samples were run though a 5-step sequential extraction technique, which exposes the soils stepwise to an increasingly aggressive chemical treatment. Each step targets a specific soil host phase: exchangeable, carbonate bound, Fe/Mn bound, organic, and residual. The results of this extraction yielded the following distribution of Cs-137 activity (percent of total): 0% exchangeable, 1-16% carbonate bound, 0-5% Fe/Mn bound, 1-5% organic, 44-67% residual, and 25-47% non-extracted. These results show that most of the Cs-137 is irreversibly bound to clays in the soil. However there are differences between soil sampling sites in regards to the amount of Cs-137 successfully extracted in the carbonate bound, Fe/Mn bound, and Organic fraction, which provides evidence that Cs-137 mobility and bioavailability is partly dependent on local soil mineralogy and chemistry.
Open Access
Isolation of reactor-borne neptunium using ion specific extraction chromatography resins and detection by gamma spectroscopy
(Colorado State University. Libraries, 2014) Rosenberg, Brett L., author; Steinhauser, Georg, advisor; Johnson, Thomas, committee member; Miller, Charles, committee member
Although actinides are the most informative elements with respect to the nature of a nuclear accident, plutonium analysis is complicated by the background created by fallout from nuclear explosions. Therefore, 239Np, a short-lived actinide (T1/2 = 2.4 d) that emits several gamma rays, is proposed herein as a suitable proxy. The most prominent photopeaks from 239Np are at 106 keV, 228 keV, and 278 keV. However, the 106 keV and 228 keV photopeaks of 239Np are also characteristic of 129mTe and 132Te, volatile fission products with half-lives of 33.6 days and 3.2 days, respectively. Although not as pronounced, there is also some spectral interference of the 278 keV peak with the 284 keV peak of 131I. The aim of this study was to screen the available ion specific resins provided by Eichrom Technologies, LLC, for the highest possible recovery and isolation of trace amounts of 239Np from samples with large amounts of fission and activation products such as radiocesium, 131I, and 129mTe. The investigated environmental media for these separations were aqueous solutions (simulating rainwater) and soil. Aqueous solutions containing 239Np and volatile radionuclides were filtered through UTEVA, Actinide, RE, and TRU Eichrom® resin columns to ascertain the most effective means of isolating 239Np from other fission and activation products for detection. This was followed up with isolation of 239Np from a soil matrix. The resins most effective for eluting 239Np from aqueous solution were UTEVA and RE (90±13% and 50±7%, respectively, calculated via the 278 keV peak yield). Isolation of 239Np from soil using these columns was found achievable only by washing out the entire 239Np-loaded stationary phase from the resin columns with acetone. This suggests that soil components can contribute to the formation of organometallic complexes within the resin matrix that enhance the retention of tetravalent neptunium. Analysis of the tellurium, cesium, and iodine content in eluates, washing solutions, and resins was conducted. Substantial fission product exclusion from eluates was found for TRU resins, RE resins, and UTEVA resins, although exclusion varied by the eluent used. In conclusion, the RE and UTEVA resins with HNO3 as a loading solution and eluent provide the best recovery of 239Np from rainwater samples while suppressing volatile radionuclides. Separation of neptunium from volatile radionuclides in soil requires further investigation, although we have demonstrated that the techniques used herein are effective at extracting neptunium from a soil matrix for detection by gamma spectroscopy.
Open Access
Neural networks for modeling and control of particle accelerators
(Colorado State University. Libraries, 2020) Edelen, Auralee Linscott, author; Biedron, Sandra, advisor; Milton, Stephen, advisor; Chong, Edwin, committee member; Johnson, Thomas, committee member
Charged particle accelerators support a wide variety of scientific, industrial, and medical applications. They range in scale and complexity from systems with just a few components for beam acceleration and manipulation, to large scientific user facilities that span many kilometers and have hundreds-to-thousands of individually-controllable components. Specific operational requirements must be met by adjusting the many controllable variables of the accelerator. Meeting these requirements can be challenging, both in terms of the ability to achieve specific beam quality metrics in a reliable fashion and in terms of the time needed to set up and maintain the optimal operating conditions. One avenue toward addressing this challenge is to incorporate techniques from the fields of machine learning (ML) and artificial intelligence (AI) into the way particle accelerators are modeled and controlled. While many promising approaches within AI/ML could be used for particle accelerators, this dissertation focuses on approaches based on neural networks. Neural networks are particularly well-suited to modeling, control, and diagnostic analysis of nonlinear systems, as well as systems with large parameter spaces. They are also very appealing for their ability to process high-dimensional data types, such as images and time series (both of which are ubiquitous in particle accelerators). In this work, key studies that demonstrated the potential utility of modern neural network-based approaches to modeling and control of particle accelerators are presented. The context for this work is important: at the start of this work in 2012, there was little interest in AI/ML in the particle accelerator community, and many of the advances in neural networks and deep learning that enabled its present success had not yet been made at that time. As such, this work was both an exploration of possible application areas and a generator of proof-of-concept demonstrations in these areas.
Open Access
Neutron fluence in a Howitzer drum and construction of a water moderated neutron irradiator
(Colorado State University. Libraries, 2024) Diaz Ruiz, Anilu S., author; Sudowe, Ralf, advisor; Johnson, Thomas, committee member; Fisher, Gwen, committee member
The Department of Environmental and Radiological Health Sciences at Colorado State University is utilizing a variety of irradiators to study the effects of ionizing on materials and tissue. Two of these are neutron irradiators based on 1 Ci and 5 Ci plutonium/beryllium (PuBe) sources, respectively. Neutron activation analysis is utilized to measure the neutron fluence at various positions in a Neutron Howitzer containing the 5 Ci source and a water tank containing the 1 Ci source. By determining the neutron flux in both systems, neutron irradiation at different intensities will become available for future research at Colorado State University. Additionally, both the drum and tank will be excellent teaching tools as they demonstrate neutron moderation, neutron shielding, material activation, and fluence measuring. Manufactured by the Nuclear-Chicago Corporation, the Model NH-3 Neutron Howitzer Drum is constructed in such a fashion that the PuBe neutron source can be moved in and out of irradiation position. In the irradiation position, two samples may be exposed to neutrons from the source by placing them in one of two horizontal ports in the drum. Both drum and ports are shielded with paraffin, which allows moderation of the neutron flux to thermal energies. In the experimental study, multiple metal foils were activated in the drum by irradiating them up to the point of measurable activity. Using a High Purity Germanium (HPGe) detector, the activity of the foils is quantified. The results of the measurements were used to calculate the neutron fluence using known neutron capture cross-sections. The calculated neutron fluence was then compared to the neutron fluence determined through a computational model of the drum using the Monte-Carlo N-Particle transport code (MCNP). Using the principles and methods practiced on the Howitzer drum, a water moderated neutron tank was constructed as a secondary neutron irradiator. The compared experimental and modeled neutron fluence spectrum in the drum were used to derive an effective model for total neutron fluence with respect to spacing from the inner end of the sample channel (x) of y = 69759e-0.17x and thermal neutron fluence of y = 12035e-0.176x.
Open Access
Neutron/muon correlation functions to improve neutron detection capabilities outside nuclear facilities
(Colorado State University. Libraries, 2016) Ordinario, Donald Thomas, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Wilson, Robert, committee member
The natural neutron background rate is largely due to cosmic ray interactions in the atmosphere and the subsequent neutron emission from the interaction products. The neutron background is part of a larger cosmic radiation shower that also includes electrons, gamma rays, and muons. Since neutrons interact much differently than muons in building materials, the muon and neutron fluence rates in the natural background can be compared to the measured muon and neutron fluence rate when shielded by common building materials. The simultaneous measurement of muon and neutron fluence rates might allow for an earlier identification of man-made neutron sources, such as hidden nuclear materials. This study compares natural background neutron rates to computer simulated neutron rates shielded by common structural and building materials. The characteristic differences between neutrons and muons resulted in different attenuation properties under the same shielded conditions. Correlation functions between cosmic ray generated neutrons and muons are then used to predict neutron fluence rates in different urban environments.
Open Access
Optimization and comparison of radioanalytical methods for the determination of radium and other alpha-emitting radionuclides in process water samples from the oil & gas industry
(Colorado State University. Libraries, 2022) Coupannec, Maelle, author; Sudowe, Ralf, advisor; Brandl, Alexender, committee member; Johnson, Thomas, committee member; Borch, Thomas, committee member
A major concern arising from hydraulic fracturing is the generation of a large volume of flowback water potentially containing various amounts of dissolved Naturally Occurring Radioactive Material (NORM). Up to four million gallons of water-based fluid is injected per well, of which 10–70% is subsequently recovered as flowback. Improving the separation and measurement of "Technologically Enhanced Naturally-Occurring Radioactive Material" (TENORM) is a priority in efficiently determining the amount of radionuclides present. An accurate assessment of radium concentration in flowback water is needed to understand potential environmental contamination from hydraulic fracturing sites and bodies of water affected by the mining industry. A significant scientific challenge in radium determination in flowback water is the presence of chemical analogues, calcium, barium, and strontium, in the flowback and produce water. Thus, the development of an accurate radium measurement and separation process is an essential step for appropriate disposal of the flowback water as regulated or non-regulated NORM-containing wastes. Non-destructive analysis of radium using direct gamma spectrometry measurements was performed on flowback water and provided accurate quantities. However, the long counting time necessary to achieve the detection limits renders the analysis impractical. Several approaches to improving radium separation and measurement methods are explored in this work. Pre-conconcentration of radium with barium sulfates was investigated to provide a more rapid gamma screening. The use of Actinide resin instead of TRU resin for column separations was studied as a means to preconcentrate Th, U, and Po in flowback and produced water from the oil and gas industry. The use of an actinide resin is expected to improve the recently developed EPA method for alpha and beta dual analysis for a complete Ra, Th, U, and Po screening or flowback water. Complete separation of radium from the wastewater matrix is ideal and will provide faster radium analysis, reducing the costs associated with handling, treatment, and disposal of wastewater. Multiple proprietary extraction chromatographic resins developed by TrisKem Int. (Bruz, France) were investigated as a function of nitric acid concentration to quantify and enhance the separation of radium from its chemical analogues. Separation of strontium from the resin matrix could easily be achieved using TKI, Sr, or Pb resin as large separation factors were obtained. The TK101 resin is promising for achieving the more difficult separation of barium from radium as the separation factor was found to be 4.3 at 0.04 M HNO3.
Open Access
Rapid acute dose assessment using MCNP6
(Colorado State University. Libraries, 2017) Owens, Andrew Steven, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Lindsay, James, committee member
Acute radiation doses due to physical contact with a high-activity radioactive source have proven to be an occupational hazard. Multiple radiation injuries have been reported due to manipulating a radioactive source with bare hands or by placing a radioactive source inside a shirt or pants pocket. An effort to reconstruct the radiation dose must be performed to properly assess and medically manage the potential biological effects from such doses. Using the reference computational phantoms defined by the International Commission on Radiological Protection (ICRP) and the Monte Carlo N-Particle transport code (MCNP6), dose rate coefficients are calculated to assess doses for common acute doses due to beta and photon radiation sources. The research investigates doses due to having a radioactive source in either a breast pocket or pants back pocket. The dose rate coefficients are calculated for discrete energies and can be used to interpolate for any given energy of photon or beta emission. The dose rate coefficients allow for quick calculation of whole-body dose, organ dose, and/or skin dose if the source, activity, and time of exposure are known. Doses are calculated with the dose rate coefficients and compared to results from the International Atomic Energy Agency (IAEA) reports from accidents that occurred in Gilan, Iran and Yanango, Peru. Skin and organ doses calculated with the dose rate coefficients appear to agree, but there is a large discrepancy when comparing whole-body doses assessed using biodosimetry and whole-body doses assessed using the dose rate coefficients.
Open Access
Statistical methods for the detection and analysis of radioactive sources
(Colorado State University. Libraries, 2014) Klumpp, John, author; Brandl, Alexander, advisor; Johnson, Thomas, committee member; Steinhauser, Georg, committee member; LaRue, Susan, committee member; Givens, Geof, committee member
We consider four topics from areas of radioactive statistical analysis in the present study: Bayesian methods for the analysis of count rate data, analysis of energy data, a model for non-constant background count rate distributions, and a zero-inflated model of the sample count rate. The study begins with a review of Bayesian statistics and techniques for analyzing count rate data. Next, we consider a novel system for incorporating energy information into count rate measurements which searches for elevated count rates in multiple energy regions simultaneously. The system analyzes time-interval data in real time to sequentially update a probability distribution for the sample count rate. We then consider a "moving target" model of background radiation in which the instantaneous background count rate is a function of time, rather than being fixed. Unlike the sequential update system, this model assumes a large body of pre-existing data which can be analyzed retrospectively. Finally, we propose a novel Bayesian technique which allows for simultaneous source detection and count rate analysis. This technique is fully compatible with, but independent of, the sequential update system and moving target model.