Research into chemical separation techniques for production of Bi-213 via irradiation of Ra-226 [abstract]

Abstract only availableBismuth 213 is an alpha radioimmunotherapeutic agent used in cancer treatment. Neutron bombardment of radium 226 is being investigated as an alternative method of producing Bi-213. For this project, a literature search of existing chemical separation steps for the production of Bis-213 for radioimmunotherapy was performed in order to optimize the combination of irradiation schemes with chemical separation steps. For the first step, the separation of actinium and radium from thorium 229 and recovery of radium for further irradiation, several successful methods were described in the literature. Organic cation exchange columns such as AG50W-X8 have traditionally been used to perform this step, but these suffer high radiolysis, which newer methods have tried to address. Some of these are an extraction chromatography method using a UTEVA column followed by a RE-resin column on a silica gel support, an inorganic titanium phosphate ion exchanger, and sublimation of the anhydrous chlorides of Th-229 and its daughter isotopes performed in a quartz tube, featuring complete separation of the elements while radium is retained at the bottom of the tube and available for further irradiation in one step. For the second part of the process, the elution of Bis-213 from an Ac-225 generator, quite a few successful techniques are described in the literature. Some of the better ones found are a multicolumn selectivity inversion generator, a renewable column, tandem column extraction chromatography, a PNNL automated generator, a MSKCC generator, an inorganic hydrated zirconium cation exchanger, and silica based resins, as well as the more traditional organic cation and anion exchange columns. A method using alpha recoil of Bis-213 from Ac-225 incorporated into a sealed isotope generator has the benefit of resulting in no radioactive, chemical, or mixed wastes, in contrast to chemical separation methods. In conclusion, several promising separation techniques were found in the literature

Design of an Automatic System for the University of Missouri Research Reactor's (MURR) Small Diameter Pneumatic-Tube (P-Tube) System [abstract]

Abstract only availableThe nuclear research facility at the University of Missouri-Columbia (MURR) has proposed a redesign of the process for irradiating the samples with INAA (Instrumental Neutron Activation Analysis) in order to increase efficiency (sample throughput), to lower the costs of experiments and to minimized dosage radiation exposure for workers. INAA was discovered in 1936 when Hevesy and Levi found that samples containing certain unusual earth elements became highly radioactive after been in contact to a source of neutrons. From this observation, they rapidly acknowledged the potential of employing nuclear neutron bombardment of samples followed by measurement of the induced radioactivity to smooth the progress of both quantitative and qualitative detection of the elements present in the samples. This new design includes a circular sample storage tray, a pneumatic gripper (for both sealing and for sending and returning of the sample from the reactor), a rotary table motor and two slider motors--one for the gripper and one for moving the sample closer to the counter machine. After the new design was conceived, the Research Reactor needed an automatic control system for the motors that were going to move the samples so they could be sent to the reactor and to the radiation detection room. My responsibility was to design the control system for the operation of the motors. The design (programming) software that I chose to use was LABVIEW programmi EMAILED 7/26/07!

Neutron activation analysis of mercury in petroleum distillates

Abstract only availableIn liquefied natural gas (LNG) plants and nitrogen rejections units (NRU) that utilize aluminum heat exchangers, mercury (Hg) contaminates can result in corrosion of equipment, poisoning of catalysts, mechanical failure, and gas leakage. The purity of the product streams from these plants is also important due to the fact that many of the resulting products such as naphtha are used as feedstock for ethylene production and various solvents. Analytical methods such as chemical extractions (CE), combustion/trap (CT), atomic fluorescent spectrometry (AFS), and inductively coupled plasma optical emission spectrometry (ICP-OES) have been used to measure mercury in petroleum distillates. These methods require extensive sample preparation. A mercury analytical method that can be applied to distillates in routine operation that minimizes mercury loss from sampling preparation is needed. Neutron Activation Analysis (NAA) is a sensitive analytical technique that can be applied to samples as received. The objective of this work was to develop a NAA procedure for testing Hg in naphtha. Virgin naphtha samples were spiked with Hg at concentrations of 20, 50, 200, 500, 1000 and 1500 ng/g. One set of samples were prepared 3 days prior to irradiation and the second set was prepared and irradiated the same day. Analysis of the samples proved that even at small samples sizes (~800 µl) concentrations of 50 to 1500 ng/g of mercury in naphtha are easily detected and give a linear response. Samples that were prepared and irradiated on the same day showed less Hg loss than those prepared 3 days prior to irradiation. Analysis of multiple (n=5) 200 ng/g samples yielded a precision of 9% RSD. The minimum detectable amount of Hg using this technique is 5 ng.NSF-REU Radiochemistr

Prompt Gamma Neutron Activation Analysis of Alternative Sensor Materials for Planetary Exploration [abstract]

Abstract only availableFaculty Mentor: Dr. William H. Miller, Nuclear Engineering and MURRPrompt gamma-rays from a thermal neutron capture reaction have been used to determine the amount of hydrogen in various materials using the prompt gamma neutron activation analyses (PGNAA) facility at Missouri Research Reactor (MURR). PGNAA uses an intense neutron beam from a nuclear reactor to measure the concentration of certain elements, including Fe, Ni, B and H. In our research, we used samples of diamond powder, a stainless steel disk and construction bolts. Half of the samples in each group were treated with either a hydrogen or a nitrogen plasma in the plasma laboratory at Polytechnic University of Puerto Rico (PUPR) while the other half remained untreated as controls. A urea SRM was used as a standard while a titanium sample was repeatedly utilized for measuring the variation in neutron flux which is a density measurement of the neutrons passing though a given region of space. The measured concentration of hydrogen present will reflect the efficiency of absorption of the substrate to hydrogen generated in the plasma. We hope to develop substitute sensor materials which will be used for planetary exploration as well as other uses for hydrogen or nitrogen impregnated substrates from plasma fields.Department of Energy's Innovations in Nuclear Infrastructure and Education Progra

Analyzing the effects of lactose on calcium absorption in premature infants using HR-ICP-Mass Spectrometry

Abstract only availableWith advances in neonatal care, premature infants are surviving at increasing rates. During the third trimester of pregnancy, the bone mineral content of infants rapidly increases. It is therefore becoming essential to accurately mimic the womb environment to maintain growth and sustain the health of premature infants as if they were in utero. Regulating calcium absorption in premature infants is crucial primarily for bone formation, as 99% of the calcium in the human body is found in the bones and the teeth. The effect of lactose containing formulas on calcium absorption in premature infants has not been well established. Concerns have been noted in the scientific community regarding lactose intolerance especially in premature infants, as lactase, the enzyme responsible for lactose digestion, is most readily detectible during the third trimester of pregnancy. In this study, in conjunction with Dr. Laura Hillman of the University of Missouri Hospital, each infant was fed lactose and maltose formulas during different weeks using a dual tracer method in which two calcium isotopes were administered, 44Ca orally and 46Ca intravenously. Urine samples were collected after 24 hours. Analysis related natural abundances of calcium isotopes to the measured values in the urine. Polyatomic ion interferences were differentiated from the calcium peaks by analyzing the samples at a resolution of 4000. Mathematical corrections for interferences caused by titanium and doubly charged strontium were determined by measuring the specific isotopes 47Ti and 87Sr++ and using known natural abundances of the interfering isotopes to correct each calcium count rate. Mathematical calculations relate the enriched isotope ratio measurements of 44Ca and 46Ca to calcium absorption. Analysis regarding the effect of lactose on calcium absorption is ongoing. Our data precision on the ICP-MS was acceptable with percent relative standard deviations (%RSD) for external precision over the course of a week at 1.4, 2.2, 0.71, and 1.4 for isotope ratios 42Ca: 43Ca, 42Ca: 44Ca, 42Ca: 46Ca, and 42Ca: 48Ca respectively. Daily internal precision (%RSD) values were .37, 1.3, .69, and 1.5. The precision shows the viability of utilizing HR-ICP-MS analysis for calcium isotope ratios.NSF-REU/NIH Program in Radiochemistr

The impact of methyl mercury on the distribution of selenium in various tissues [abstract]

Abstract only availableFaculty Mentor: J. David Robertson, ChemistryThere is evidence that a regimen of dietary selenium provides protection against the toxic biological effects of methyl mercury.  Animal studies suggest that a potential mechanism is that selenium causes the redistribution of methyl mercury from critical organ tissue to muscle.   In vivo experiments were conducted to assess the correlation of Se and MeHg in previously tested rat nail samples and various rat organ tissue samples. Groups (n=24) of weanling male Long Evans rats were fed torula yeast based diets containing either deficient Se, or supplemented with sodium selenite to adequate or enriched levels of Se.  The group of 24 was then separated into smaller groups (n=8).  Each separated group was given diets prepared with no methyl mercury, low amounts of methyl mercury or high amounts of methyl mercury.  The rats were then sacrificed and the brain, liver, kidneys, pituitary, testes and nails were collected.  The MeHg and Se content of each tissue was determined by standard comparator neutron activation analysis using the 74Se(n,γ)75 Se and the 202Hg(n,γ)203Hg reactions.  The organ tissue samples were irradiated for 50 hours at a flux of ca. 5 X 1013 n·cm-2·s-1 and allowed to decay for ten or more days.  The samples were then measured using a Canberra spectrometer and compared to the data from the nail samples.  The ratio of selenium to mercury in the nails and organ tissue will be used to verify if the nail is a viable biological marker for selenium and mercury uptake in various organ tissues

Engineering review and calibration of devices to measure coolant flow through irradiation positions at MURR [abstract]

Abstract only availableFaculty Mentor: Dr. William Miller, Nuclear Engineering at MURRTechnetium-99m (Tc-99m) is widely used for medical imaging applications around the world. This useful isotope can be produced by creating molybdenum-99 (Mo-99) and letting it decay via beta particle emission to the wanted Tc-99m. Today most major producers use High Enriched Uranium (HEU) to create the Mo-99. In an attempt to demonstrate a method that does not use weapons-grade uranium, the University of Missouri Research Reactor (MURR) is trying to produce Mo-99 isotopes by irradiating Low Enriched Uranium (LEU) foils instead of the normally used HEU. Because the target (LEU) is still 19.75% enriched, approximately 0.75kW/g of heat will be released during the process and because we do not want it to overheat or melt we need to know how much cooling water is passing by the target and how much heat is taken away from it. There are a lot of ways to measure water flow velocity. In this case, the goal is to get accurate measurement in a small non-uniform tube 30 feet underwater on a research nuclear reactor. The bulk flow over the desired positions is available, and with this some calculations can be made to get the velocity on the irradiation positions. These calculations then can be compared with an actual measurement in pressure drop from where a flow velocity then can be derivate. To further increase the precision of the results a Constant Temperature Anemometer (CTA) will be used to measure the actual velocity of the flow in certain areas of the irradiation points. The CTA has to be calibrated before it can be implemented. This project is an engineering review of the various flow measurement methods and a calibration of the device chosen to make local fluid velocity measurements in the irradiation positions

The Interactions Between Selenium and Methyl Mercury in Rat Tissues [abstract]

Abstract only availableFaculty Mentor: J. David Robertson, chemistryMethyl mercury (MeHg) is a neurotoxin that is prevalent in marine ecosystems worldwide. Deleterious effects to humans from MeHg exposure include loss of neurons, microcavitation, edema in the cerebral cortex and death. The fetal brain is particularly vulnerable, as MeHg crosses the placental barrier. There is evidence that dietary selenium plays a protective role against the toxicity of MeHg. Epidemiologists can study the health risks of MeHg and Se by using the nail as an index of exposure. In this study, instrumental neutron activation analysis was used to measure levels of Se and Hg in a rat model to determine how the interactions between Se and MeHg affect the nail as a biological monitor. Groups (n=24) of male weanling Long Evans rats were fed diets of deficient, adequate or enriched levels of Se. These groups were then subdivided into 3 groups of 8 and fed diets with either no MeHg, low levels of MeHg or high levels of MeHg. The rats were terminated and the brain, kidney, liver, pituitary gland, testes and nail were collected. The samples were freeze dried, weighed and sealed into quartz vials. The samples, quality controls and standards were irradiated at a neutron flux of ca. 5x1013 n·cm-2·s-1 for 50 hours at the University of Missouri Research Reactor and were allowed to decay for several days. The reactions involved were 202Hg (n,γ) 203Hg and 74Se (n,γ)75Se. Samples were counted using an automated sample changer with an HPGe detector, and peak areas were determined interactively with Genie ESP spectroscopy software. Ultimately, we hope to correlate the tissue and nail studies to ascertain if the nail is an accurate biomarker for measuring MeHg and Se exposure in various tissues

Computational Evaluation of LEU Conversion for Production of Tc-99m. [abstract]

Abstract only availableFaculty Mentor: Dr. William Miller, Nuclear EngineeringThe imaging radioisotope Technetium-99m (Tc-99m) is currently being used about 10,000 times daily in the United States.  There are no facilities in the U.S. capable of producing Tc-99m, rather the parent nuclide Molybdenum-99 must be imported from Canada.  Feasibility studies are being performed to determine the capabilities to irradiate and process a low enriched uranium (LEU) target using existing Missouri University Research Reactor (MURR) facilities.  Computational analysis of this new process at the MURR included the use of ORIGEN to estimate the production of both Mo-99 and the many other isotopes that are produced in the fission process.  The data from ORIGEN was analyzed to predict shielding requirements using the Health Physics Companion code package.  Additional work was done to automate the analysis of ORIGEN output using C++ to facilitate easy use for further studies. Calculated total dose rates are about 0.08 and 0.002 Rem/hr at 1cm and 1m respectively.  This analysis suggests that the projected 5.25” of lead plus 0.75” of tungsten should provide sufficient shielding