•Soluble uranium removal by zero valent iron groundwater from nuclear fabrication facility.•Environmental restoration of uranium contaminated water.•Zero valent iron nanoparticles used for environmental remediation.In this study, nanoscale zero valent iron I-NZVI was investigated as a remediation strategy for uranium contaminated groundwater from the former Cimarron Fuel Fabrication Site in Oklahoma, USA. The 1 L batch-treatment system was applied in the study. The result shows that 99.9% of uranium in groundwater was removed by I-NZVI within 2 h. Uranium concentration in the groundwater stayed around 27 μg/L, and there was no sign of uranium release into groundwater after seven days of reaction time. Meanwhile the release of iron was significantly decreased compared to NZVI which can reduce the treatment impact on the water environment. To study the influence of background pH of the treatment system on removal efficiency of uranium, the groundwater was adjusted from pH 2–10 before the addition of I-NZVI. The pH of the groundwater was from 2.1 to 10.7 after treatment. The removal efficiency of uranium achieved a maximum in neutral pH of groundwater. The desorption of uranium on the residual solid phase after treatment was investigated in order to discuss the stability of uranium on residual solids. After 2 h of leaching, 0.07% of the total uranium on residual solid phase was leached out in a HNO3 leaching solution with a pH of 4.03. The concentration of uranium in the acid leachate was under 3.2 μg/L which is below the EPA's maximum contaminant level of 30 μg/L. Otherwise, the concentration of uranium was negligible in distilled water leaching solution (pH = 6.44) and NaOH leaching solution (pH = 8.52). A desorption study shows that an acceptable amount of uranium on the residuals can be released into water system under strong acid conditions in short terms. For long term disposal management of the residual solids, the leachate needs to be monitored and treated before discharge into a hazardous landfill or the water system. For the first time, I-NZVI was applied for the treatment of uranium contaminated groundwater. These results provide proof that I-NZVI has improved performance compared to NZVI and is a promising technology for the restoration of complex uranium contaminated water resources.

Concentrations of Ag, Au, Cu and Zn were determined via neutron activation analysis in ore prospecting samples from the Cozamin and Tizapa Mexican mines. Ag concentrations were determined by applying cyclic epithermal neutron activation analysis. The method combined with an automated fast-pneumatic transfer system allows increased sample through-put which improves the analytical precision in silver prospecting. Combinations of thermal, epithermal and Compton suppression NAA were used to improve signal-to-noise ratios. Mining depths with significantly higher levels of Ag were determined. Reference material concentrations for quality control were found to be in good agreement with the certified values.

This work details the design criteria, construction, controls, and optimization of the 14 MeV neutron irradiation facility at the University of Texas, built with the motivation of performing neutron activation analysis on samples with short half-lives. The facility couples a D–T neutron generator with a pneumatic transfer system capable of transit of approximately one second between source and detector, while the cyclic automated nature allows for many irradiation/count trials with any number of samples, translating to significantly improved counting statistics.

Uranium samples of various enrichments have been passively counted on the University of Texas detector gamma–gamma coincidence system. By observing gamma rays emitted from 235U and its daughters compared to gamma rays emitted by 238U daughters and comparing the data to standards of known enrichments, a technique has been developed to take a uranium sample of unknown enrichment and passively count it to determine its uranium isotopic concentration. Because the gamma rays from 235U are generally in the low-energy regime, there is a strong susceptibility to background interferences, especially from the Compton background produced from higher energy gamma rays. Other interferences, such as those from the decay series of uranium also exist for 235U gamma rays. In this light, we have collected data using list-mode to produce two-dimensional gamma–gamma coincidence spectra, which allows us to gate the low-energy gamma rays from 235U with gamma rays that are in coincidence. In doing this, much of the low energy interferences are reduced, and one can analyze the 235U gamma rays with high precision. Because of the high density of uranium, self-shielding has significant effects especially in the low-energy regime. To correct for this attenuation the detector system has been modeled by MCNP and self-shielding factors have been calculated across the energy spectrum. A big advantage to this method is the capability of performing this analysis with small (<1 g) samples in a non-destructive and relatively inexpensive manner. If necessary, this analysis can be performed within 24 h if an urgent nuclear forensics scenario arises.

Biological materials containing trace amounts of mercury and selenium were examined using neutron activation analysis. They were analyzed using Compton suppression and γ–γ coincidence counting. The 279 keV photopeak of activated mercury (203Hg) was analyzed in order to observe the mercury content in these samples. Selenium, an element found in many biological samples, interferes with the analysis of 203Hg when activated (75Se). Because the selenium interference comes from a cascading emission, Compton suppression was utilized to reduce this interference. In order to fully characterize the selenium content in the samples, γ–γ coincidence was used which reduced the background and eliminated bremsstrahlung interference produced from neutron activated phosphorous through the 31P(n, γ)32P reaction which is a pure beta emitter. As a result, we determined the mercury and selenium concentrations in three standard reference materials, which contain varying ratios of mercury to selenium concentrations. This study also showed that these types of concentrations can be determined from small (<500 mg) sample masses. Further work needs to be done on wet samples that require dehydration, as mercury can be lost through this process.

Neutron activation analysis (NAA) remains an excellent technique to introduce undergraduate students to nuclear science and engineering coming from different academic areas. The NAA methods encompass an appreciation of basic reactor engineering concepts, radiation safety, nuclear instrumentation and data analysis. At the Nuclear Engineering Teaching Lab at the University of Texas at Austin we have continued to provide opportunities through outreach programs to Huston-Tillotson University in Austin and Florida Memorial University in Miami Gardens, both Historically Black Colleges and Universities, and Southwestern University in Georgetown, Texas. Furthermore, in the past four years we have established a strong educational collaboration with the École Nationale Supérieure d’Ingénieurs de Caen (ENSICAEN), France. Undergraduate students at ENSICAEN are required to have an internship outside of France. While many of the students stay in neighboring European countries others have chosen the United States. The cornerstone of these programs is to secure a relationship with each institution through clear educational and research objectives and goals.

Cesium is a member of the Group I alkali metals, very reactive earth metals that react vigorously with both air and water. The chemistry of cesium is much like the chemistry of neighboring elements on the periodic table, potassium and rubidium. This close relation creates many problems in plant-life exposed to cesium because it is so easily confused for potassium, an essential nutrient to plants. Radioactive 134Cs and 137Cs are also chemically akin to potassium and stable cesium. Uptake of these radioactive isotopes from groundwater by plant-life destroys the plant-life and can potentially expose humans to the radioactive affects of 134Cs and 137Cs. Much experimental work has been focused on the separation of 137Cs from uranium fission products. In previous experimental work performed a column consisting of Kel-F supporting tetraphenylboron (TPB) was utilized to separate 137Cs from uranium fission products. It is of interest at this time to attempt the separation of 134Cs from 0.01M EDTA using the same method and Neoflon in the place of Kel-F as the inert support. The results of this experiment give a separation efficiency of 88% and show a linear relationship between the column bed length and the separation efficiency obtained.

Phosphates, naturally containing trace amounts of uranium, were examined using direct γ-ray spectrometry. Both normal and Compton-suppressed counting modes were utilized. The 1001 keV photo peak of the second daughter of 238U was chosen because of its isolation from other, potentially interfering peaks. The findings suggest that with the aid of Compton suppression, it is possible to quantify low uranium levels in phosphates using samples sizes of order 10 grams within an accuracy of 5%. The uranium content was determined in several sample types and was found to range from 60±4 to 70±8 μg/g, depending on the sample composition. This investigation also considered the effects of sample size, counting time, and counting technique as sources of precision maximization. This work has shown that only a small amount of phosphate is needed to determine the constituent concentration, instead of the standard several hundred grams of material.

Over the last six years through a Department of Energy Radiochemistry Education Award Program (REAP) we have developed a completely web-based course in nuclear and radiochemistry given at the University of Texas at Austin. This course has had nuclear and radiation engineering and chemistry graduate students. While the course also has an extensive laboratory component only the lectures are web based. The lectures begin with a historical introduction of radiochemistry followed by two movies on Madame Curie. This is followed by the usual lectures on radioactivity, fundamental properties, radioactive decay, decay modes, and nuclear reactions. As section on radioactive waste management and nuclear fuel cycle is also presented. Lectures in neutron activation analysis, geo- and cosmochemistry, and plutonium chemistry have also been developed. All lectures are in power point with many animations and a significant number of solved problems. All students are required to make a short oral presentation on some aspect of nuclear and radiochemistry in their research or a chosen topic.

The Compton suppression system (CSS) has been thoroughly characterized at the University of Texas’ Nuclear Engineering Teaching Laboratory (NETL). Effects of dead-time, sample displacement from primary detector, and primary energy detector position relative to the active shield detector have been measured and analyzed. Also, the applicability of Poisson counting statistics to Compton suppression spectroscopy has been evaluated.

•Soluble uranium removal by zero valent iron in freshwater and waste water.•Environmental restoration of uranium contaminated water.•Zero valent iron nanoparticles used for environmental remediation.Uranium (U) has been released to surface soil and groundwater through military and industrial activities. Soluble forms of U transferred to drinking water sources and food supplements can potentially threaten humans and the biosphere due to its chemical toxicity and radioactivity. The immobilization of aqueous U onto iron-based minerals is one of the most vital geochemical processes controlling the transport of U. As a consequence, much research has been focused on the use of iron-based materials for the treatment of U contaminated waters. One material currently being tested is nanoscale zero-valent iron (nZVI). However, understanding the removal mechanism of U onto nZVI is crucial to develop new technologies for contaminated water resources. This review article aims to provide information on the removal mechanism of U onto nZVI under different conditions (pH, U concentration, solution ion strength, humic acid, presence of O2 and CO2, microorganism effect) pertinent to environmental and engineered systems, and to provide risk or performance assessment results with the stability of nZVI products after removal of U in environmental restoration.

•Bauxite residue (Red Mud) has a radiological risk.•235U, 238U, 232Th and 40K were determined using neutron activation analysis.•Radiation dose levels were modeled by MCNP.This study employs thermal and epithermal neutron activation analysis (NAA) to quantitatively and specifically determine absorption dose rates to various body parts from uranium, thorium and potassium. Specifically, a case study of bauxite residue (red mud) from an industrial facility was used to demonstrate the feasibility of the NAA approach for radiological safety assessment, using small sample sizes to ascertain the activities of 235U, 238U, 232Th and 40K. This proof-of-concept was shown to produce reliable results and a similar approach could be used for quantitative assessment of other samples with possible radiological significance. 238U and 232Th were determined by epithermal and thermal neutron activation analysis, respectively. 235U was determined based on the known isotopic ratio of 238U/235U. 40K was also determined using epithermal neutron activation analysis to measure total potassium content and then subtracting its isotopic contribution. Furthermore, the work demonstrates the application of Monte Carlo Neutral-Particle (MCNP) simulations to estimate the radiation dose from large quantities of red mud, to assure the safety of humans and the surrounding environment. Phantoms were employed to observe the dose distribution throughout the human body demonstrating radiation effects on each individual organ.

•Development of LaBr3:Ce scintillation detectors for a gamma-gamma coincidence.•Energy gating was successfully employed in reducing the background.•ɣ-ɣ coincidence can be used in the identification of fission products in spent nuclear fuel.A radiation detection system consisting of two cerium doped lanthanum bromide (LaBr3:Ce) scintillation detectors in a gamma-gamma coincidence configuration has been used to demonstrate the advantages that coincident detection provides relative to a single detector, and the advantages that LaBr3:Ce detectors provide relative to high purity germanium (HPGe) detectors. Signal to noise ratios of select photopeak pairs for these detectors have been compared to high-purity germanium (HPGe) detectors in both single and coincident detector configurations in order to quantify the performance of each detector configuration. The efficiency and energy resolution of LaBr3:Ce detectors have been determined and compared to HPGe detectors. Coincident gamma-ray pairs from the radionuclides 152Eu and 133Ba have been identified in a sample that is dominated by 137Cs. Gamma-gamma coincidence successfully reduced the Compton continuum from the large 137Cs peak, revealed several coincident gamma energies characteristic of these nuclides, and improved the signal-to-noise ratio relative to single detector measurements. LaBr3:Ce detectors performed at count rates multiple times higher than can be achieved with HPGe detectors. The standard background spectrum consisting of peaks associated with transitions within the LaBr3:Ce crystal has also been significantly reduced. It is shown that LaBr3:Ce detectors have the unique capability to perform gamma-gamma coincidence measurements in very high count rate scenarios, which can potentially benefit nuclear safeguards in situ measurements of spent nuclear fuel.