Mountain Scholar :: Browsing by Author "Brandl, Alexander, committee member"

Browsing by Author "Brandl, Alexander, committee member"

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Open Access
A comparison of methods to derive aggregated transfer factors: tested using wild boar data from the Fukushima prefecture
(Colorado State University. Libraries, 2017) Anderson, Donovan, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Hess, Ann, committee member
In March of 2011, the Fukushima Daiichi disaster released airborne radioactive material dominated by Cs-134 and Cs-137. When the radionuclides settled, they contaminated soil and plants, with wild boar also becoming contaminated through various pathways. An estimate of the radiocesium concentration in wild boar tissues can be obtained from an aggregated transfer factor based on soil contamination levels. The aggregated transfer factor (Tag) for purposes of this study, is the ratio of Cs-137 concentration in wild boar tissues (Bq kg-1) divided by the Cs-137 surface contamination of soils (Bq m-2). In this study, two methods were used to estimate the Tag values, and a comparison was made to determine which method reduced uncertainty. Both methods rely on harvesting and measuring radiocesium in wild boar tissues (bicep femoris muscle). The radiocesium value used for soil, however, was different in the two methods. One was obtained from a public database of samples collected by the Japanese government in 2015. Oftentimes, the soil sample paired with the wild boar trap site were not within the home range of the wild boar, reducing accuracy of the predicted radiocesium concentration levels in the animal. The other method used soil samples collected at the point of wild boar capture. The purpose of this study is to ascertain if the use of the database radiocesium soil concentration values is of sufficient granularity to provide a useful estimate of Tag values. The mean Tag value calculated in the Fukushima prefecture for wild boar were 2.3×10-3 m2 kg-1 fresh weight. The research revealed that the database radiocesium concentration values for soil (Bq m-2) used in calculating aggregated transfer factors, do not accurately represent the containment levels in the wild boar. Collecting soil samples within the home range of the animal reduces uncertainty in calculating Tag values to estimate whole body contamination levels of a wild boar. Our data complements and supports the existing monitoring programs conducted by the National and Prefecture governments in Japan by showing lower concentrations of cesium in soil and wild boar within decontaminated areas.
Open Access
A comparison of the use of sodium iodide and lanthanum bromide scintillation crystals for airborne surveys
(Colorado State University. Libraries, 2014) Bailey, Derek M., author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Milton, Stephen, committee member
The Environmental Protection Agency (EPA) Aerial Spectral Environmental Collection Technology (ASPECT) program performs aerial radiological and chemical characterization of geographical regions of interest. Airborne surveys are performed to characterize environmental radionuclide content, for mineral exploration, as well as for emergency scenarios such as major releases or lost sources. Two radiological detection systems are used by the ASPECT team for gamma-ray detection and characterization: lanthanum bromide [LaBr3(Ce)] and sodium iodide [NaI(Tl)] scintillation systems. An aerial survey of a uranium mine in the western United States was performed using both NaI(Tl) and LaBr3(Ce) detection systems. Analyses of the survey data were performed with RadAssist software and applying International Atomic Energy Agency (IAEA) airborne gamma ray mapping guidelines. The data for the survey were corrected for cross-over, which is spectral interference from higher energy photons as a result of Compton scattering, height attenuation, cosmic ray contribution to signal, and Radon contribution to signal. Two radiation survey contours were generated from each discrete data set. Based on analysis of the uranium mine survey results, LaBr3(Ce) produced a product comparable to that of NaI(Tl). The LaBr3(Ce) detection system contained 1/16th the scintillating volume and had a total system weight that was 1/4th that of the NaI(Tl) system. LaBr3(Ce) demonstrated a clear advantage over NaI(Tl) detectors in system mobility, and weight factors in airborne gamma ray spectroscopy.
Open Access
A net-risk approach to displacement and reoccupation decision making
(Colorado State University. Libraries, 2019) Braley, Gerald Scott, author; Johnson, Thomas E., advisor; Brandl, Alexander, committee member; Fisher, Gwen, committee member; Sudowe, Ralf, committee member
Decision makers and planners have a large body of information available concerning most aspects of a radiation disaster. International and national standards organizations, as well as national and local level policies and plans provide little guidance about the risks involved in relocating a population from a radiologically contaminated area. Populations displaced after all types of disasters have demonstrated poorer health outcomes, both physiological and psychological, than their non-displaced peers. These include a greater risk of diabetes and greater rates of post-traumatic stress disorder and depression when compared with other populations who experienced the disaster but were not relocated. Methodologies for population-level radiation dose prediction have improved, with recent data from contaminated areas in Japan providing real-world information about radiation doses. These improvements have not yet made their way into policies and guidance. The objective of this work is to quantify and incorporate multiple forms of risk, radiological and non-radiological, into a single model to improve decision making and minimize harm connected to displacement from and reoccupation of radiologically contaminated areas after a disaster.
Open Access
Active radiation detectors for use in space beyond low earth orbit: spatial and energy resolution requirements and methods for heavy ion charge classification
(Colorado State University. Libraries, 2017) McBeth, Rafe A., author; Borak, Thomas, advisor; Brandl, Alexander, committee member; Ray, Andrew, committee member; Homrighausen, Darren, committee member
Space radiation exposure to astronauts will need to be carefully monitored on future missions beyond low earth orbit. NASA has proposed an updated radiation risk framework that takes into account a significant amount of radiobiological and heavy ion track structure information. These models require active radiation detection systems to measure the energy and ion charge Z. However, current radiation detection systems cannot meet these demands. The aim of this study was to investigate several topics that will help next generation detection systems meet the NASA objectives. Specifically, this work investigates the required spatial resolution to avoid coincident events in a detector, the effects of energy straggling and conversion of dose from silicon to water, and methods for ion identification (Z) using machine learning. The main results of this dissertation are as follows: 1. Spatial resolution on the order of 0.1 cm is required for active space radiation detectors to have high confidence in identifying individual particles, i.e., to eliminate coincident events. 2. Energy resolution of a detector system will be limited by energy straggling effects and the conversion of dose in silicon to dose in biological tissue (water). 3. Machine learning methods show strong promise for identification of ion charge (Z) with simple detector designs.
Open Access
Analysis of potential airborne radionuclide emissions during and after fires through contaminated soil areas on the INL
(Colorado State University. Libraries, 2021) Williams, Connor, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Lindsay, James, committee member
The risk of wildfires burning through legacy soil contamination areas of the Idaho National Laboratory (INL) facility with consequent airborne radiological releases has been a concern for some time and this concern has only increased in recent years with an increasing number and size of wildfires burning through the property. The question of personnel safety has been raised in terms of firefighters and other first responders who might be in close proximity to an ongoing fire as well as the health risks to facility staff and members of the general public. As a result, this study seeks to update the current soil nuclide inventory of the known legacy contamination sites which pose a fire risk as well as update previous fire resuspension studies made of INL contamination sites through the use of updated modeling techniques and inputs available in more recent literature. Baseline soil contamination values were developed for the contaminated areas starting with average measured radionuclide concentrations in soil, using in-situ gamma spectroscopy or decay correcting the best available data from previous reports. Soil-to-plant uptake fractions from the literature were used to estimate radionuclide concentrations in plants growing on the sites. Worst case estimates of plant biomass were used to yield release estimates during a fire. Doses to first responders or other high-exposure individuals were estimated through a comparison to the minimum soil screening concentrations calculated specifically for the INL facility in the literature. This study involved using dynamic dispersion models to determine the minimum soil and plant concentration, for various common nuclides found at INL, which would be necessary to produce an exposure of 10 mrem or greater either during a fire due to release of radionuclides from plant tissue, or after a fire due to resuspension of rootless soil. Based on the relatively low level of soil radionuclide concentrations in even the most contaminated sites, the low soil-to-plant transfer coefficients of the specific measured nuclides remaining in the soil and the likely quick dispersion and dilution of any released nuclides in the smoke/dust column, the overall exposure is likely to be small. Therefore, it is hypothesized that that any measurable radiological doses which could be expected to any given individual would be well below current occupational or public exposure limits and thus would not present a health hazard.
Open Access
Beam-driven co-linear X-band energy booster (CXEB) for a compact FEL
(Colorado State University. Libraries, 2017) Sipahi, Taylan, author; Milton, Stephen V., advisor; Biedron, Sandra G., advisor; Menoni, Carmen S., committee member; Brandl, Alexander, committee member
Achieving compact, efficient and cost-effective particle accelerators is overall major goal of the community to help propel future projects forward. In the realm of particle accelerators that enable both the high-energy physics and light-source communities, achieving the highest energy with the brightest beams in the shortest distance is most important and it is here where a paradigm shift is needed. Achieving high energies in a shorter distance (higher gradients) than presently achievable is important for even small laboratory settings, i.e. universities or industries desiring light sources, as it would permit an affordable cost. While there are several methods being considered for compact, efficient particle accelerators, it was chosen to pursue a unique application of X-band (11.7 GHz) RF cavities as they are capable, due to their intrinsic high shunt impedance, of generating high gradients with relatively low input power. A novel idea that can push the Colorado State University's (CSU) Advanced Beam Laboratory's beam energy up from the present 6 MeV to over 32.6 MeV, without the need of additional, expensive X-band power sources was conceived. The concept is called the co-linear X-band energy booster (CXEB) and it relies on the use of X-band structures powered by the beam that is already available from the facility's existing L-band (1.3 GHz) linear accelerator system. Also, this proposed system can provide electron beam to a compact free-electron laser (FEL) at CSU. The overall FEL system is quite compact and comparatively cost-effective given the fact that the existing L-band infrastructure already exists.
Open Access
Calibration of an irradiation facility
(Colorado State University. Libraries, 2017) Marcinko, Rion, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Duncan, Colleen, committee member
The objective of this research is to provide accurate reliable data for use in an irradiation facility and present findings in a manner useful to operators. The intended use of the irradiator and irradiator protocols dictate a need for a well-known administered dose. Dose rates from two independent methods were investigated at multiple distances away from the source. First, the irradiation platforms were examined for "hot spots" using Gafchromic © film to provide a qualitative estimate of the dose distribution. A quantitative assessment of doses was then performed using Fricke dosimetry (a primary standard). Finally, MCNP modeling was used to simulate irradiation at the various measured points and intermediate points in the radiation field. The results were used to provide dose rates within the radiation field for future researchers, and demonstrated how precision and accuracy vary using theoretical (MCNP) and measurement methodology. MCNP simulation matched the Fricke measurements within 10% for the first two positions explored, then diverged upon further movement from the source.
Open Access
Deposition of strontium-90 in soil and vegetation at various locations surrounding the Fukushima Daiichi Nuclear Power Plant
(Colorado State University. Libraries, 2015) Ball, Joseph E., author; Steinhauser, Georg, advisor; Brandl, Alexander, committee member; Gudmestad, Robert, committee member
As a result of the 2011 Honshu earthquake, a tsunami formed off the coast of Japan that overtook the Fukushima Daiichi Nuclear Power Plant (FDNPP). This tsunami caused a cooling system failure at FDNPP. Due to this failure, a meltdown and subsequent release of radioactivity occurred. This project attempts to determine if 90Sr was released during the meltdown and could be detected in the surrounding environment. Vegetation and soil samples were collected from eight locations near the FDNPP ranging from 0 km to 40 km. The samples were subjected to a radiochemical separation to isolate 90Sr from other potential radionuclides in the samples. This was done to eliminate interference from those radionuclides in our analysis of 90Sr in the Hidex 300SL liquid scintillation counter (LSC). Results of the analysis determined with 95% confidence that 90Sr was detectable in both vegetation and soil samples within 4.1 km of the FDNPP. The highest levels of 90Sr activity concentration fall in-between the activity concentrations of naturally-occurring radionuclides in the earth's upper crust and do not pose a significant health threat to humans due to ingestion.
Open Access
Dose reconstruction in the large Japanese field mouse using electron paramagnetic resonance spectroscopy of tooth enamel
(Colorado State University. Libraries, 2020) Davis, Mariah, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Gelfand, Martin, committee member
Electron spin resonance (ESR) analysis of tooth enamel is recognized as a reliable method for lifetime dose reconstruction, particularly in human tooth enamel. While the use of ESR to reconstruct dose is well understood for human tooth enamel, the reliability and usefulness of dose reconstruction using ESR in mouse tooth enamel has not been as thoroughly studied. This paper aims to resolve this gap in knowledge concerning the use of the tooth enamel from the Large Japanese Field Mouse as acting dosimeter using EPR spectroscopy. Methods of tooth preparation were analyzed to find a preparation method that resolved a baseline shift or slope in output signals of preliminary samples. Use of purity EDTA (ethylenedinitrilotetraacetic acid, disodium salt dihydrate) was initially found to reduce an observed baseline shift and slope in the output spectrum. Subsequent samples treated with EDTA, however, again saw baseline shifts. More needs to be done to analyze appropriate methodology to reduce the baseline shift, and to further determine the suitability of mouse teeth for ESR spectroscopy for reconstruction of lifetime dose.
Open Access
Effects of major inorganic constituents of asphalt on the rapid determination of plutonium
(Colorado State University. Libraries, 2024) Chunko, Raissa, author; Sudowe, Ralf, advisor; Brandl, Alexander, committee member; Quackenbush, Sandra, committee member
In case of a nuclear incident, standard radioanalytical techniques must be available to analyze radionuclides in unusual matrices. Radiochemical analysis of samples in standard matrices of soil, water, and air are very well established; however, much less research has been conducted on the effect of unusual matrices such as steel, concrete, glass, and asphalt. In the event of a detonation of an improvised nuclear device (IND) in an urban environment, the standard separation techniques used for plutonium separations from asphalt samples originating from roadways and roofing shingles must rigorously be tested to provide useful insight on the characteristics of the special nuclear material. Batch studies were used to determine the changes in uptake of plutonium on extraction chromatography resins in the presence of trace metal components found in asphalt including aluminum, iron, and manganese at possible ranges found in asphalt samples. In these studies, selected cations with a +3-oxidation state had some interesting effects on the uptake of plutonium on the extraction chromatography resins. Aluminum increased the sorption of plutonium only on DGA and TRU resins especially at rising concentrations. Iron very unexpectedly increased the sorption of plutonium on all resins particularly at high concentrations. Additionally, metals found in the +3 oxidation state were shown to interfere with the recovery of plutonium from column studies conducted due to the synergistic effects. From this data, the contaminates found in asphalt with a +3-oxidation state may either compete with plutonium or give rise to a "salting out" effect that increases the sorption on the extraction chromatography resins and will need to be considered during the development of a rapid separation technique for plutonium from asphalt samples.
Open Access
Electron paramagnetic resonance dosimetry and the use of Japanese wild boar tooth enamel as a dosimeter for reconstruction of lifetime external absorbed doses from the Fukushima Exclusion Zone
(Colorado State University. Libraries, 2018) Harshman, Amber, author; Johnson, Thomas E., advisor; Brandl, Alexander, committee member; Sudowe, Ralf, committee member; Fisher, Gwen, committee member
The goal of this study was to establish characteristics of Japanese wild boar tooth enamel in the region of 0.25 – 12.0 Gy and to reconstruct external doses to wild boar native to the Fukushima Exclusion Zone using Electron Paramagnetic Resonance Dosimetry. The significance of Japanese wild boar in their ecosystem and their position within the trophic hierarchy make the wild boar a species of particular importance and therefore the focus of this study. Dose response, linearity, and variability of enamel originating from various wild boar were investigated. Radiation dose response of Japanese wild boar tooth enamel in the range of 0.25 – 12.0 Gy was found to be linear, and the average variation in dose response between teeth originating from the same boar specimen was 30%. Analysis of dose response of permanent and deciduous tooth enamel revealed a statistically significant difference in both the degree of dose response and also variation. No statistically significant difference in dose response was found in permanent molar teeth of boar of differing ages or in boar of different sex. Doses were successfully reconstructed with large associated uncertainties. The critical level dose value for the calibration curve was 1.0 Gy, and the detection limit dose was 1.8 Gy, suggesting that this method would be more beneficial for boar with lifetime doses over 1 Gy. The method of reconstructing external doses using EPR dosimetry with tooth enamel from Japanese wild boar as dosimeters has proven to be a viable method which can be used to reconstruct doses to wildlife in accident-stricken areas in the absence of alternative dosimetry.
Open Access
Electronic dosimeter and thermoluminescent dosimeter correlation study at Catawba Nuclear Station
(Colorado State University. Libraries, 2014) Edquist, Britt Alyssa, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Biedron, Sandra, committee member
Duke Energy's nuclear fleet is comprised of seven nuclear plants. The dosimetry program at every plant includes a comparison of the dose recorded by the TLDs and EPDs at the end of each quarter. EPD over-response is desirable to a degree because the over-response offers a higher dose estimate; however, too great of an over estimate obscures the actual dose a worker receives. An EPD/TLD correlation study was conducted to quantify and identify factors contributing to excess EPD over-response and offer recommendations to improve the EPD/TLD correlation. The EPD/TLD correlations at Catawba Nuclear Station (CNS) (York, SC) were markedly higher than the EPD/TLD correlations at other Duke Energy nuclear plants. The purpose of this study was to investigate the EPD/TLD correlation experienced at CNS. Assemblies, comprised of a phantom (a one gallon plastic jug filled with water) with a V2/V3 Mirion 2000S EPD, V4 Mirion 2000S EPD and TLD inside of a plastic bag that was zip tied to the phantom, were placed in strategic locations within the CNS auxiliary building. Dose rates in the CNS auxiliary building ranged from approximately 10 μSv/h (1 mrem/h) to 350 μSv/h (35 mrem/h). Assemblies were removed after seven days and the dose from the EPDs and TLDs were determined and recorded. Both the V2/V3 and V4 EPDs over-responded compared to the TLD. The V4 over-response was found to be greater than the V2/V3 over-response. Reducing the V4 EPD bias from 15% to 7% would improve the correlation between EPD and TLD doses while still permitting some over-response, allowing for more meaningful EPD dose estimates.
Open Access
Evaluation of dose enhancement due to CuATSM uptake in hypoxic environments with external radiation
(Colorado State University. Libraries, 2019) Martinez, Stephen K., author; Leary, Del, advisor; Boss, Keara, committee member; Brandl, Alexander, committee member; De Long, Susan, committee member; Kato, Takamitsu, committee member
Most solid tumors contain areas of chronic hypoxia caused by limited diffusion of oxygen from tumor microvasculature. Hypoxic regions have been found to be radioresistant and their presence results in a worse prognosis for tumor control. Metal radiosensitizers have been employed to alleviate the radioresistance in hypoxic tumors by increasing dose through additional photoelectrons and Auger cascades. In recent years, gold nanoparticles (GNP) have been explored for their potential as an enhancer of external beam radiation and become the standard-bearer for the treatment modality; however, GNP have lower cellular uptake in anoxic and hypoxic conditions than under normoxic conditions. Additionally, the large size of nanoparticles decreases their diffusivity, reducing their ability to penetrate into tumor tissue distant from vasculature. The chelator diacetylbis (N(4)-methylthiosemicarbazonato) copper II (CuATSM) provides the potential to overcome the hypoxic barrier by preferentially depositing copper into tumor regions previously inaccessible to treatment. The characteristics of CuATSM have led to its utilization in positron emission tomography (PET) imaging of hypoxic regions. These PET images have also been investigated as a method for dose painting, amplification of intensity modulated radiation therapy (IMRT) dose to hypoxic regions. Additionally, radioactive ⁶⁴CuATSM has been investigated for implementation in brachytherapy for hypoxic tumors. The Auger electrons ejected upon decay of the radioisotope have been shown to be highly damaging to DNA. The intention of this study is to evaluate the potential of CuATSM as an external beam radiosensitizer. This project investigates radiosensitization of CuATSM by Monte Carlo (MC) modeling of different energy external beam spectra available clinically with Electron Gamma Shower (EGSnrc) and Geometry and Tracking (Geant4) and evaluating dose enhancement with CuATSM. These MC models are informed by and evaluated against cell models. Research indicates that CuATSM at high concentrations with low energy photons has efficacy for enhancing dose in hypoxic tumor regions.
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
ICARUS cosmic ray tagger efficiency
(Colorado State University. Libraries, 2024) Boone, Tyler N., author; Wilson, Robert, advisor; Fairbank, William, committee member; Mooney, Michael, committee member; Brandl, Alexander, committee member
The ICARUS Cosmic Ray Tagger (CRT) was constructed with the goal to tag cosmogenic muons passing through the ICARUS Time Projection Chamber (TPC). Construction and commissioning of the detector began in Fall 2019 with the Side CRT North wall and continued for several years through the installation of the Top CRT. In this thesis I will summarize my contributions to the CRT system and describe a measurement of the installed CRT detection efficiency using the TPC.
Open Access
Inventory dynamics and soil factors affecting soil-to-plant ¹³⁷Cs transfers in Fukushima forest ecosystems
(Colorado State University. Libraries, 2020) Zhang, Jian, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Sudowe, Ralf, committee member; Pilon-Smits, Elizabeth, committee member
The objective of this study was to understand the soil factors affecting soil-to-plant transfer factors in understory plant species as well as their contribution to the total 137Cs inventory in aboveground biomass within the Fukushima forest ecosystem. Radiocesium contamination from the March 2011 accident at the Fukushima Da-ichi Nuclear Power Station (FDNPS) was initially deposited on the forest canopies with deposition into the soil occurring over the next few years through litterfall and precipitation. Measurements taken from the Yamakiya site in 2014 show that the contribution of understory plants to the total inventory of radiocesium in aboveground biomass was very low compared to the dominant Japanese cedar trees. However, measurements were not taken in other affected sites within Fukushima prefecture as well as potential change in concentrations of radiocesium in understory biomass since 2014. Data for evaluating the transfer factors was obtained through sampling of soil and understory plants at the Yamakiya, Tsushima, Tomioka, Okuma, and Yokomuki sites inside Fukushima Prefecture. Both 134Cs and 137Cs measurements were collected, however 134Cs concentrations were negligible compared to 137Cs so only 137Cs data was considered. 137Cs content was determined using gamma spectroscopy of the soil and plant samples and to find the concentration of bioavailable 137Cs within the root profile of the understory plants as well as 137Cs concentration within the understory plant itself. The soil and plant 137Cs concentration was used to determine the soil-to-plant uptake factors for the sampled understory species as well as the contribution of the understory plants to the total 137Cs inventory in aboveground biomass. The effect of soil exchangeable [K+], exchangeable [Cs+], exchangeable 137Cs activity concentration, total 137Cs activity concentration, and pH on 137Cs uptake by understory plants was determined through the soil-to-plant uptake factors at the various sample sites. The same data was used to find the 137Cs deposition in the soil, 137Cs inventory in Yamakiya, and patterns between plant activity concentration between plant species. Soil measurements showed a logarithmic decrease in 137Cs activity concentration with decreasing soil depth. Measurements also supported a 4.39 year effective half-life using GIS and Nuclear Regulatory Authority data, however using IER data a radiological half-life of 30.17 years was supported instead. The majority of 137Cs inventory in Yamakiya was found to be in soil (80.54%) and trees (18.52%) with understory plants making up a negligible contribution. This contribution by trees was much higher than the one found in previous years. For understory plants, it was found that there are higher 137Cs activity concentrations in the more metabolically active portions of the plants. 137Cs was a significant contributing factor across all understory plant species in predicting the soil to plant transfer factors. The ability to properly estimate the activity concentration of understory plants using only the one soil factor can contribute to faster estimation of potential 137Cs concentrations in plants or uptakes by herbivores in areas contaminated by 137Cs. The further understanding of 137Cs dynamics in forest ecosystems will assist in creation of a long-term forest radiation contamination management strategy.
Open Access
Investigation of exposure rate discrepancies between energy compensated Geiger Mueller tubes and pressurized ionization chambers due to muon and anti-muon cosmic particles
(Colorado State University. Libraries, 2017) Gift, Matthew, author; Johnson, Thomas E., advisor; Brandl, Alexander, committee member; Fisher, Gwenith, committee member
Energy compensated Geiger Mueller (GM) tubes and pressurized ionization chambers are two types of gas filled detectors that measure radiation dose or exposure but operate on different physical principles. Energy compensated GMs are gaining popularity because they are less expensive and more durable than pressurized ionization chambers, however, an exposure rate discrepancy may exist between the two instruments. At an elevation of about 1524m (5,000 ft), energy compensated GM tubes were observed to have nearly a 2-fold over-response to background measurements when compared to measurements performed by pressurized ionization chambers. The goal of this research is to investigate the expected exposure rate discrepancy due to muon and anti-muon cosmic particles, since they are the largest background contributor to dose at low elevations. Theoretically calculated average chord length and stopping power, as well as, Monte Carlo N-Particle 6 were used to investigate and characterize the exposure rate from muons and anti-muons. The calculated exposure rate contribution of muons and anti-muons for the background measurement of the energy compensated GM tube was negligible and is not expected to be the primary cause for the over-response. More research is needed to characterize the discrepancy.
Open Access
Investigation of storage-phosphor autoradiography for alpha emitters on different types of filters
(Colorado State University. Libraries, 2019) Sorcic, Ashley, author; Sudowe, Ralf, advisor; Brandl, Alexander, committee member; Omur-Ozbek, Pinar, committee member
Numerous incidents in the past have resulted in the release of radioactive contamination into the environment, some of which require continuous monitoring decades later. Past and potential future incidents encourage governments and regulating agencies to develop procedures and methods to deal with nuclear emergencies, decontamination and decommissioning, and historical preservation in the face of a possibly dangerous environment. One technique which may assist in forensics and clean-up efforts is digital autoradiography. Digital autoradiography is based on the creation of luminescence due to the interaction of ionizing radiation with the storage phosphor. The resulting image can provide information about the amount and spatial distribution of the radioactivity in a sample. While the technique is typically used for the imaging of beta-emitting radionuclides, it can also be used for alpha emitters. Previous work has shown a correlation between the radioactivity of the sample and the intensity of the light emitted by the phosphor. In addition, it was observed that the luminosity varied for different alpha emitting isotopes. The current work extended this research to other alpha emitting isotopes and the effect of the energy of the emitted alpha particle on the response of the phosphor screens. In addition the effect of different types of air filters as source material was investigated, as well as the response of Multi-Sensitive storage phosphor screens compared to SuperResolution screens. The last major variable considered was how wrinkled the filters were; this variable was first considered shortly after the sample preparations were complete.
Open Access
Investigation of the extraction of stable ⁴⁵Sc and carrier free ⁴⁴Sc for theranostic applications
(Colorado State University. Libraries, 2022) Brown, Morgan L., author; Sudowe, Ralf, advisor; Brandl, Alexander, committee member; Zadrozny, Joseph, committee member
Scandium is an element of major interest when it comes to theranostic applications. There are mainly two isotopes of scandium utilized in medical applications, Sc-44 and Sc-47. Sc-44 is a positron emitter and is used for imaging, while Sc-47 is utilized as a beta emitter for targeting tumors. Together, the pair make up a theranostic agent. This research mainly focuses on Sc-44. To utilize the isotope after production, it must first be separated and purified from target material, in this case titanium. One of the quickest and most efficient way to separate radioisotopes, especially for medical purposes, is extraction chromatography. The goal of this research is to understand and possibly improve the separation of scandium from titanium by employing a variety of different chromatographic resins in a fast manner. Previous studies in the literature yielded data from several groups that examined the uptake of scandium and titanium on an extraction chromatographic resin based on a tetraoctyl diglycolamide, DGA. These groups employed either stable or radioactive scandium for their experiments. While the uptake of titanium was consistent between the studies, all groups have reported different values for the uptake of scandium. The aim of this part of the work is to compare both the uptake of stable and radioactive scandium to further elucidate the discrepancies between the studies reported in the literature. Radioactive Sc-44 for tracer studies will be obtained by "milking" a Ti-44 generator in regular intervals. Both stable and radioactive results obtained in this research will be compared.
Open Access
Laser damage thresholds of ex-vivo pig and rabbit corneas at 2.5 and 2.7 μm with 8 nanosecond laser pulse duration
(Colorado State University. Libraries, 2011) Guo, Yuanqing, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Bernstein, Elliot R., committee member
With the rapid development of advanced laser technology, lasers have been widely applied to research, industry, medicine, military, and consumer products, particularly in the infrared (IR) spectral region. Consequently, safety has been a major concern not only for people who develop and operate lasers, but also for people who use products integrated with lasers. To establish specific laser safety standards for eye protection, many laser safety studies have been conducted for determination of the retina damage threshold in the visible spectral region. The damage threshold for the cornea, a major damage target in the IR wavelength range, however, has not been well established, especially for short laser pulse durations (ns). The purpose of this work was to determine the damage thresholds of the cornea at 2.5 and 2.7 micrometer with 8 ns laser pulses using ex-vivo pig and rabbit eye models. In addition, due to the difference of water absorption coefficients at these two wavelengths (the water absorption coefficient at 2.7 micrometer is about 4-5 times of that at 2.5 micrometer), the role of water absorption for corneal damage was estimated through comparison of damage thresholds at these two wavelengths. Based on our experimental results, both pig and rabbit eyes have similar damage thresholds (ED50) of 0.81 J/cm2 at 2.7 micrometer and 3.66 J/cm2 at 2.5 micrometer. The ratio between the damage thresholds at these two wavelengths is 4.5, which is in good agreement with the ratio of the water absorption coefficients at these two wavelengths. This finding suggests that water absorption in the IR spectral region plays an important role in the damage threshold of the cornea. In addition, temperature changes on the cornea induced by laser energy absorption at varied radiant exposure were monitored through an infrared camera (ThermaCAMTM S65). Results indicate that the increase of temperature on the corneal surface is proportional to the radiant exposure, and with a measured damage threshold of 0.7oC above ambient.