Missouri University Research Reactor Research Articles

Ionization Efficiency Measurement and Optimization of a Thermal Ion Source for Radioisotope Electromagnetic Separation

An available supply of high-specific-activity radioisotopes was identified by the U.S. Department of Energy as a critical priority in the development and eventual deployment of next-generation medical diagnostic and cancer therapy tools. A radioisotope mass separator, located at the Missouri University Research Reactor Center, was developed to provide radioactive ion beams for the separation and production of high-specific-activity lanthanides used in radiopharmacology. Experiments characterizing the ionization efficiency of a thermal ion source supporting the production of high-specific-activity 153Sm are reported. With the goal of maximizing ion current while maintaining beam stability, experiments with the test ion source expand upon previously reported data from a titanium prototype ion source. Experimental results of various factors affecting ion source performance, such as diameter of the extraction orifice, ionizer geometry, ionizer temperature, and sample evaporation rate, are presented.

Development of an Experimentally Validated MCNP6 Model for 11C Production via the 14N(p,α) Reaction Using a GE PETtrace Cyclotron

The General Electric (GE®) PETtrace 860 cyclotron at the Missouri University Research Reactor (MURR) facility is used extensively for medical and research radioisotope production. However, no model exists of its performance, and the proton beam’s energy and spatial distribution are unmeasured. Here, an MCNP6 model was developed to improve upon the performance of the cyclotron target systems that are routinely utilized for research and medical radioisotope production. Since the cyclotron beam energy and profile have a significant impact on the efficiency and character of radioisotope production, the MURR cyclotron proton beam energy was measured using high-purity copper stacked foil activation to be 14.6 ± 0.2 MeV, a significant reduction from the stated 16.4 MeV. Phosphor plate imaging was also used to radiographically image the distribution of radioisotope production within the copper foils and characterize the beam spatial and intensity profile. Total target activity was quantified by trapping the 11C on a solid adsorbent and measuring the amount in an ion chamber. Effective target densities were calculated for irradiations conducted with beam currents between 5 and 40 μA. The measured beam and target characteristics were used to develop an MCNP6 model of 11C production. Through use of the model, it was determined that the targets were, at most, 41% efficient as a thick target design resulting in up to 11.80-MeV average protons impinging on the target walls leading to potential contamination from hot ion recoils.

OBSIDIAN SUB-SOURCES AT THE ZARAGOZA-OYAMELES QUARRY IN PUEBLA, MEXICO: SIMILARITIES WITH ALTOTONGA AND THEIR DISTRIBUTION THROUGHOUT MESOAMERICA

We present data produced through archaeological and geological survey, as well as geochemical analysis of the Zaragoza-Oyameles obsidian source area located on the northern and western flanks of the Los Humeros Caldera in eastern Puebla, Mexico. One result of the intensive archaeological surface survey of this obsidian source area was the identification of 117 obsidian flow-band exposures. Geologic samples from 40 of these were submitted for instrumental neutron activation analysis. Eighty-five projectile points collected from the surface were characterized using portable X-ray fluorescence. These analyses identified three sub-sources: Z-O1, Potreros Caldera, and Gomez Sur. The Gomez Sur sub-source appears chemically similar to the previously identified Altotonga source, located 25 km to the northeast. Results of the geological survey help elucidate the relationship of Altotonga obsidian with the Zaragoza-Oyameles source area. The data from the three sub-sources are compared to all consumer site data attributed to the Zaragoza-Oyameles source in the Missouri University Research Reactor database. Results indicate that the majority of consumer samples throughout Mesoamerica match the Z-O1 sub-source, while 4 percent match the Potreros Caldera sub-source. This information, combined with the Gomez Sur data, is discussed in terms of economic relations with the regional center of Cantona. Obsidian procurement and distribution may have been more nuanced than previously modeled. We suggest that a number of potentially independent communities in addition to Cantona may have been involved in distributing this obsidian throughout Mesoamerica.

Neutron Scattering Studies of Lithium-Ion Diffusion in Ternary Phosphate Glasses

We have studied the diffusion mechanism of lithium ions in glassy oxide-based solid state electrolytes using elastic and quasielastic neutron scattering. Samples of xLi 2 SO 4 -(1-x)(Li 2 O-P 2 O 5 ) were prepared using conventional melt techniques. Elastic and inelastic scattering measurements were performed using the triple-axis spectrometer (TRIAX) at Missouri University Research Reactor at University of Missouri and High Flux Backscattering Spectrometer (HFBS) at NIST Center for Neutron Research, respectively. These compounds have a base glass compound of P 2 O 5 which is modified with Li 2 O. Addition of Li 2 SO 4 leads to the modification of the structure and to an increase lithium ion (Li + ) conduction. We find that an increase of Li 2 SO 4 in the compounds leads to an increase in the Lorentzian width of the fit for the quasielastic data, which corresponds to an increase in Li + diffusion until an over-saturation point is reached ( 2 SO 4 ). We find that the hopping mechanism is best described by the vacancy mediated Chudley-Elliot model. A fundamental understanding of the diffusion process for these glassy compounds can help lead to the development of a highly efficient solid electrolyte and improve the viability of clean energy technologies.

Refining the Accuracy of Predicting Physics Parameters at Research Reactors due to the Limitations in the Energy Balance Method Using MCNP and the ENDF Evaluations

A detailed study at the Missouri University Research Reactor indicates that limitations in the energy balance methodology, using the Monte Carlo N-Particle transport code (MCNP) and the Evaluated Nuclear Data Files (ENDF), affect the accuracy of predicting important parameters for reactor physics studies. In the case of fuel conversion, key parameters such as flux and power level cannot be measured until the converted reactor is operating. Therefore, predictions with well-known uncertainties are essential for an effective conversion. However, due to inherent energy balance problems in the isotopic heating evaluations for materials within various fuel matrices, in particular the U-10Mo monolithic fuel, the values for the predicted parameters could vary more than previously estimated. In particular, the total recoverable energy per fission, which directly affects the calculated flux for a given power level, appears to be underestimated by MCNP's energy balance method. Therefore, an alternative methodology for predicting the total recoverable energy of a system was investigated. Results for the proposed low-enriched uranium U-10Mo configuration show that there is a 3.02-MeV difference between the total recoverable energy per fission from this work and that from the MCNP predictions. A similar comparison for the present highly enriched uranium UAlx configuration shows a difference of 1.24 MeV.

Intercalibration of physical neutron dosimetry for the RA-3 and MURR thermal neutron sources for BNCT small-animal research

New thermal neutron irradiation facilities to perform cell and small-animal irradiations for Boron Neutron Capture Therapy research have been installed at the Missouri University Research Reactor and at the RA-3 research reactor facility in Buenos Aires, Argentina. Recognizing the importance of accurate and reproducible physical beam dosimetry as an essential tool for combination and intercomparisons of preclinical and clinical results from the different facilities, we have conducted an experimental intercalibration of the neutronic performance of the RA-3 and MURR thermal neutron sources.

Ceramic Production and Exchange in Late/Terminal Formative Period Oaxaca

Patterns of Late/Terminal Formative period (ca. 500 B.C.–A.D. 300) ceramic exchange in Oaxaca are examined through instrumental neutron activation analysis (INAA). Samples of 453 Late/Terminal Formative period sherds were submitted to the Missouri University Research Reactor for INAA to determine elemental composition. The sherds came from 20 excavated sites and two surveys in the following regions: the Valley of Oaxaca, Mixteca Alta, Mixteca Baja, lower Río Verde Valley, and Cuicatlán Cañada. Selected for the study were vessel fragments from three recognized paste categories: grayware (gris), fine brownware (café fino), and creamware (crema). We also sampled clays and sherds from known sources in four modern pottery-making towns in the Oaxaca Valley. The research adds to the INAA database for Oaxaca by identifying the chemical signatures of six source groupings that we can link to specific regions and, in two cases, to particular source zones within regions. The evidence from chemical composition and typology indicates continuity in resource use and production practices in both Atzompa and Coyotepec from pre-Hispanic into modern times. The data show that the exchange of ceramics in Late/Terminal Formative Oaxaca was multidirectional, with ceramics imported both to and from the Oaxaca Valley.

Radiochemistry at the University of Missouri-Columbia: A joint venture with chemistry, nuclear engineering, molecular biology, biochemistry, and the Missouri University Research Reactor (MURR)

The United States, the Department of Energy (DOE) and its National Laboratories, including the Pacific Northwest National Laboratory (PNNL), are facing a serious attrition of nuclear scientists and engineers and their capabilities through the effects of aging staff. Within the DOE laboratories, 75p of nuclear personnel will be eligible to retire by 2010. It is expected that there will be a significant loss of senior nuclear science and technology staff at PNNL within five years. PNNL's nuclear legacy is firmly rooted in the DOE Hanford site, the World War II Manhattan Project, and subsequent programs. Historically, PNNL was a laboratory where 70p of its activities were nuclear/radiological, and now just under 50p of its current business science and technology are nuclear and radiologically oriented. Programs in the areas of nuclear legacies, global security, nonproliferation, homeland security and national defense, radiobiology and nuclear energy still involve more than 1,000 of the 3,800 current laboratory staff, and these include more than 420 staff who are certified as nuclear/radiological scientists and engineers. This paper presents the current challenges faced by PNNL that require an emerging strategy to solve the nuclear staffing issues through the maintenance and replenishment of the human nuclear capital needed to support PNNL nuclear science and technology programs.

99mTc‐HYNIC‐Bombesin (7‐14)NH2: Radiochemical Evaluation with Co‐ligands EDDA (EDDA = Ethylenediamine‐N,N′‐diacetic Acid), Tricine, and Nicotinic Acid

Bombesin (BBN) is a peptide exhibiting high affinity for the gastrin releasing peptide receptor (GRPr), which is over‐expressed on a variety of human tumors including breast, prostate, lung and pancreatic cancers. The specific aim of this study was to identify a new 99mTc‐radiolabeled BBN analogue based upon the bifunctional chelating ligand HYNIC (2‐hydrazinonicotinamide) that might be used as a noninvasive tool for diagnosis of GRP receptor‐positive tumors. In this study, HYNIC‐β‐Ala‐BBN(7‐14)NH2 and HYNIC‐5‐Ava‐BBN(7‐14)NH2 were synthesized using traditional solid phase peptide synthetic techniques. The newly‐formed conjugates were radiolabeled using 99mTc in the presence of different coligands including tricine, ethylenediamine diacetic acid (EDDA), tricine/EDDA, and tricine/nicotinic acid. Radiolabeling conditions (i.e., pH, temperature, and reaction time) were optimized and evaluated by ITLC and reversed‐phase HPLC. This material is the result of work supported with resources and the use of facilities at the Radiopharmacy Center, Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), São Paulo, SP, Brazil, the Harry S. Truman Memorial Veterans Hospital, Columbia, MO, the University of Missouri-Columbia School of Medicine Departments of Radiology and Internal Medicine, and the Missouri University Research Reactor, Columbia, MO.

The effect of high-dose-rate X-rays on E. coli 0157:H7 in ground beef

The emergence of pathogens in today's world has increased the need for new, portable, nonthermal sterilization technologies. The University of Missouri, Columbia in cooperation with the Institute of Electrophysics, Ekaterinburg, Russia, have built and tested a new accelerator based on solid-state opening switches for the disinfection of pathogens in food. The accelerator utilizes a new solid-state opening switch to generate 40 ns, 2OO-keV electron beam pulses. These pulses were then converted to Bremsstrahlung X-rays using an integral X-ray converter. The efficacy of treating E. coli 0157:H7. In ground beef was tested by irradiating frozen ground beef with the high-dose-rate 10/sup 7-6/ rads/s X-ray pulses. Comparison studies were also done with a Cobalt-60 source located at the Missouri University Research Reactor. The results of the study are presented in this paper.

Caddo Ceramics from 41CV41A at Fort Hood, Coryell County, Texas

Prehistoric Caddo ceramics made in Northeast Texas after ca. A.D. 900 were widely traded in Texas, and other parts of the Caddoan area, being found in some quantity on North central, East central, central, and inland Southeast Texas archeological sites. They were also traded with prehistoric peoples in the Midwest, the southeastern U.S., and the southern Plains. However, the ceramic evidence for prehistoric Caddoan trade and exchange with other Native Americans has not been systematically compiled and studied for the prehistoric and historic periods. Consequently, it is impossible to confidently discuss the scope, timing, or direction of trade/exchange between Caddoan groups and surrounding non-Caddoan communities, or explore changes in the nature of social and economic relationships between particular Caddo groups and with other prehistoric peoples. Over the last several years, I have been attempting to systematically document archeological infonnation on the distribution and character of Caddoan ceramic sherds and vessels both within and outside what is considered the southern Caddoan archeological area. This documentation effort has included instrumental neutron activation analysis by the Missouri University Research Reactor, petrographic analyses, and studies of ceramic styles and pastes. Here, I discuss Caddo ceramics from 41CV4JA that were recently recovered in archeological investigations by Prewitt and Associates, Inc. at Fort Hood in Central Texas.

The effect of an enriched selenium-76 supplement on dietary monitors and glutathione peroxidase activity

The objective of this study was to determine if a stable enriched tracer of Se-76 could be used to establish the delay time between a dietary intake of selenium and its appearance in various matrices. Selenium, an essential trace element, has been investigated at the Missouri University Research Reactor (MURR) for several years. Several matrices have been studied to determine selenium status in humans; these include fingernails, toenails, blood, hair, and urine. A cohort of five women and seven men was utilized for this study. Each subject ingested selenium supplements which were enriched in Se-76 (96.48%). Fingernails, toenails, whole blood, and blood sera were collected as biochemical indicators. Selenium concentrations and glutathione peroxidase activities were determined in blood sera and whole blood to monitor the effect of the selenium supplement in these matrices. Selenium concentrations were determined in fingernails and toenails prior to supplementation and for several months afterward to determine the delay time for the appearance of selenium. The effects of the selenium supplement on the selenium concentrations of the fingernails, toenails, whole blood, and blood sera and the effect of the supplement on glutathione peroxidase activity will be reported.

Analysis of Shell-Tempered Pottery Replicates: Implications for Provenance Studies

Archaeometric methods such as provenance studies must be predicated on understanding the processes that underlie the production of this information. This study focuses on element-based provenance studies of Mississippian-period pottery, which are complicated by the fact that this pottery generally was tempered with crushed shell in different amounts and of unknown species composition. Experiments conducted at the Missouri University Research Reactor (MURR) have documented elemental dilution and enhancement effects of adding shell temper to clay. Mathematical corrections previously have been employed to correct for shell-temper effects. Results of physical, chemical, and mathematical approaches to eliminating the effects of shell tempering indicate that mathematical methods, based on a firm knowledge of shell composition, provide the most efficient correction.

Efficient production of high specific activity 64Cu using a biomedical cyclotron

Copper-64 ( T 1 2 = 12.7 h ) is an intermediate-lived positron-emitting radionuclide that is a useful radiotracer for positron emission tomography (PET) as well as a promising radiotherapy agent for the treatment for cancer. Currently, copper-64 suitable for biomedical studies is produced in the fast neutron flux trap (irradiation of zinc with fast neutrons) at the Missouri University Research Reactor. Access to the fast neutron flux trap is only possible on a weekly basis, making the availability of this tracer very limited. In order to significantly increase the availability of this intermediate-lived radiotracer, we have investigated and developed a method for the efficient production of high specific activity Cu-64 using a small biomedical cyclotron. It has been suggested that it may be possible to produce Cu-64 on a small biomedical cyclotron utilizing the 64Ni(p,n) 64Cu nuclear reaction. We have irradiated both natural nickel and enriched (95% and 98%) Ni-64 plated on gold disks. Nickel has been electroplated successfully at thicknesses of ~20–300 mm and bombarded with proton currents of 15–45 μA. A special water-cooled target had been designed to facilitate the irradiations on a biomedical cyclotron up to 60 μA. We have shown that it is possible to separate Cu-64 from Ni-64 and other reaction byproducts rapidly and efficiently by using ion exchange chromatography. Production runs using 19–55 mg of 95% enriched Ni-64 have yielded 150–600 mCi of Cu-64 (2.3–5.0 mCi/μAh) with specific activities of 94–310 mCi/μg Cu. The cyclotron produced Cu-64 had been used to radiolabel PTSM [pyruvaldehyde bis-(N 4-methylthiosemicarbazone), used to quantify myocardial, cerebral, renal, and tumor blood flow], MAb 1A3 [monoclonal antibody MAb to colon cancer], and octreotide. A recycling technique for the costly Ni-64 target material has been developed. This technique allows the nickel eluted off the column to be recovered and reused in the electroplating of new targets with an overall efficiency of greater than 90%.

Two-bent-crystal technique in neutron small angle scattering

The design of two-bent-crystal small angle neutron scattering configurations is discussed. Neutron optics computations for experiment optimization are presented. An arrangement implemented at the Missouri University Research Reactor is described. It consists of a curved pyrolytic graphite premonochromator followed by two curved thin silicon wafers diffracting from (111) and (220) planes, respectively.

Investigation of the appearance of supplemental enriched Se-76 using the human nail as a dietary monitor

The principal objective of this study was to determine if the use of a stable enriched tracer of Se-76 could be used to determine the delay time between a dietary intake of selenium and its appearance in fingernails and toenails. Selenium is an essential trace element in human nutrition. It has been studied at the Missouri University Research Reactor (MURR) for the past 15 years using an Instrumental Neutron Activation Analysis (INAA) technique. The principal route of human exposure to selenium is through the diet. Selenium concentrations of nails, blood, hair, and urine have been used as indicators of dietary selenium intake. In this study, a cohort consisting of seven men and five women ingested three selenium supplements of 150 μg each over a three day period. The selenium was enriched in Se-76 (96.48%) and ingested as selenite in orange juice following an overnight fast. Fingernails and toenails were collected prior to the selenium supplementation and for several months afterward to be used as biochemical indicators. The peak76Se concentration in the fingernails and toenails occurred at 19–23 and 16–32 weeks after supplementation, respectively.

Quasielastic gamma-ray scattering from glycerol

The Mossbauer scattering instrument at the Missouri University Research Reactor (MURR) has been used to study the liquid dynamics of glycerol as a function of temperature. The measurements were made by observing the Mossbauer gamma rays from the 46.5-keV level in183W scattered in the direction corresponding to the first liquid structure peak atQ=1.36 A−1. The widths of the Mossbauer velocity spectra were found to be quasielastically broadened by 3.1 μeV at 24 °C up to 55 μeV at 113 °C. The broadening varied quadratically with temperature above the melting point, but showed a linear dependence when plotted versus the absolute temperature divided by the viscosity. As discussed by Singh and Mullen, this latter dependence is expected in the continuous diffusion limit. The original analysis by Singwi and Sojlander was carried out for a diffusing Mossbauer ion, where the observed cross section is the Fourier transform of the self-correlation function. Our case requires the use of the paircorrelation function. Quantitative calculations as well as further experiments are needed.

Experiments and possibilities with super-intense Mössbauer sources

We have been able to prepare Mossbauer sources having intensities ranging from 10 to 100 Ci for several isotopes, using the Missouri University Research Reactor Facility, MURR. These sources offer rich opportunities for carrying out precision Mossbauer experiments as well as high collimation scattering experiments. Using such intense sources, we have been able to measure the interference parameter of the 46.5 keV Mossbauer transition to about 1% accuracy. We find it to be about 10% greater than predicted by theory, which may have significant implications for time reversal violation experiments. We have also been able to show that the Bragg scattered recoilless fraction scattered from (200) planes of sodium chloride crystals is 94% of that found for the (600) reflection, even though the integrated intensity of this reflection is more than a factor of 10 less than that of the (200) reflection. We highlight some of the experiments that we have carried out and discuss some of the enticing possibilities for the future with sources in the 10–1000 Ci range. One of these is the possibility of doing Mossbauer spectroscopy with a stationary source and absorber, moving only a monochromating crystal filter along the direction of the reciprocal lattice vector associated with the Bragg reflection being used.

Magnetic neutron scattering (invited)

The application of neutron scattering techniques to magnetic problems is reviewed. We will first discuss diffraction techniques used to solve magnetic structures, as well as to measure magnetic form factors, order parameters, critical phenomena, and the scattering from low-dimensional systems. We will also discuss inelastic scattering techniques, including polarized beam methods, utilized to determine the spin dynamics of various materials. Information will be provided about the types of spectrometers available at the user-oriented national facilities located at Argonne National Laboratory, Brookhaven National Laboratory, Los Alamos National Laboratory, The National Institute of Standards and Technology, and Oak Ridge National Laboratory, as well as the spectrometers at the Missouri University Research Reactor.

Design of microfocusing bent-crystal double monochromators

Design relations are given for double bent-crystal monochromators ensuring both spatial microfocusing and focusing in reciprocal space in powder diffraction. The choice of crystals for monochromators for microfocus stress scanning in steels is discussed. Design computations for an instrument at the Missouri University Research Reactor (MURR, thermal neutron flux 10 14 n/cm 2 s) with small-mosaic Cu(200) crystals are presented. The spot size can be brought down to 2.5 × 4 mm, with a peak flux at focus approaching 10 8 n/cm 2 s.