Search

Introduction: Following critiques of multiple personal contamination events from entries into the Oak Ridge National Laboratory's Spallation Neutron Source Transfer Bay, it was considered that the most likely causes for contamination were personal protective clothing doffing errors or moisture (sweat) allowing contamination to wick through the protective clothing. Radiological protection staff looked more closely, however, at the specific area of the clothing where contamination was highest; under enhanced lighting and photochromic manipulation, there appeared to have been some type of moisture in the area. Recognizing the possibility that moisture may have allowed for migration of contamination through the clothing, further experiments were undertaken to determine under which conditions this transport might have occurred., Objective: The objective for this work was to identify the susceptibility of different types of personal protective clothing to various liquids encountered in the workplace., Method: Several tests were performed to determine if perspiration had enabled migration of contamination and to identify what other liquids might have affected contamination transport. Two layers of personal protective clothing were subjected to static conditions and dynamic conditions to include active rubbing of the materials while wet. Food dye added to each of the liquids tested enabled visual indications of liquid breakthrough. Additional tests were conducted to see if solid contamination could be transported through the materials along with the liquids., Results: All but one type of non-rubberized personal protective clothing in use at Oak Ridge National Laboratory were permanently compromised to some extent by the solvents used for decontamination., Conclusion: It was determined that most common cleaning agents immediately and permanently destroyed the hydrophobic nature of several of the tested protective clothing materials, potentially allowing for radioactive contamination to penetrate through the material to the worker. Work around wet surfaces or performing wet decontamination will only be performed in protective clothing known to prevent transport of the wetting agent.

Following large-scale nuclear power plant accidents such as those that occurred at Chernobyl (Ukraine) in 1986 and Fukushima Daiichi (Japan) in 2011, large populations are living in areas containing residual amounts of radioactivity. As a key session of the ConRad conference, experts were invited from different disciplines to provide state-of-the-art information on the topic of "living in contaminated areas." These experts provided their different perspectives on a range of topics including radiation protection principles and dose criteria, environmental measurements and dose estimation, maintaining decent living and working conditions, evidence of health risks, and social impact and risk communication. A short summary of these different perspectives is provided in this paper.

Bentonite is considered for use as a buffer material in the final disposal repositories of radioactive waste. Long-lived 135Cs with a half-life of 2.3 × 106 years is a key radionuclide in high-level waste, and lots of 137Cs with a half-life of 30.2 years exists in low-level waste. Therefore, the adsorption of Cs on bentonite is a critical issue in evaluating the long-term safety of radioactive waste disposal. In this study, EXAFS techniques were used to characterize the time-dependent process from the beginning of adsorption to equilibrium. From the results of this study, we found changes including to the Cs adsorption sites, the Cs-O distance between Cs and the oxygen atom, and that the adsorption of Cs ions occurred before the reaction reached equilibrium. The fraction of OS complexes when Cs was adsorbed on bentonite can refer to the CN (Cs-O1st)/CN (Cs-O2nd) ratio of coordination numbers, and this study found that the OS complex was the major adsorption species when Cs adsorbed onto bentonite. In addition to the ratio CN (Cs-O1st)/CN (Cs-O2nd) providing information on the adsorption site, we also discussed the change of Cs-O1st and Cs-O2nd bond distances to identify the adsorption sites at different times. Comparing the XRD patterns of montmorillonite and bentonite, we found that the interlayer collapsed after Cs was adsorbed onto montmorillonite, but it expanded after Cs was adsorbed onto bentonite. From the results of EXAFS fitting, we found that the movement of Cs ions was from regular interlayer sites to expanded interlayer sites, which caused the interatomic distance of Cs-O2nd to decrease with an increase in time. It was revealed that the adsorption of Cs on bentonite occurred in two steps. The first step includes the rapid uptake of Cs by attachment to the oxygen atoms of the H2O molecules at the regular interlayer sites, especially for the OS complexes. The second step includes a slower process where dehydrated Cs ions move from the regular interlayer sites to the expanded interlayer sites. In this study, Cs L3-edge EXAFS spectroscopy was conducted for the Cs adsorbed on bentonite to identify the Cs adsorption sites over time, as this is important in evaluating the mobility of Cs in the environment. These results are beneficial in finding the process of Cs adsorption on bentonite, which could be used for the design of the final disposal of spent nuclear fuel.

The speciation of radioactive tritium (T) in a naturally-established subtropical loblolly pine forest that has been irrigated with highly-contaminated pond water for the last 20 years is reported. This irrigation project was created to limit the underground transport of a tritium-rich plume which also contains low levels of toxic organics, metals and radionuclides such as carbon-14 (14C) from a nearby low-level waste burial ground. The levels of tritiated water (HTO) in the wood cores were not influenced by recent irrigation activities. However, the tritium levels in the last 20 years of tree growth were more than 3-fold higher than that of tritium in the older growth. This was due to recent irrigation with organic-bound tritium (OBT)-rich water and subsequent accumulation of high levels tritium as OBT relative to tissue HTO. High levels of pond irrigation water OBT resulted from biogenic processes that converted HTO to OBT. Data for 14C that were acquired for some of the forest materials indicated that the processes controlling the movement and accumulation of 14C in this system are somewhat different than that of tritium. Spectroscopic characterization of tree core tissue of <20 years in age found no explanation for the unusually wide dark growth rings. It was concluded that the trees were over-irrigated based on results from other published studies with wood from severely-flooded areas. Although HTO is indeed toxic to biota, OBT represents a relatively greater hazard to biota because it can be bioaccumulated and retained for long periods of time in living tissues.

This work describes the molecular characterization of the interaction mechanism of a bentonite yeast isolate, Rhodotorula mucilaginosa BII-R8, with curium(III) as representative of trivalent actinides and europium(III) used as inactive analogue of Cm(III). A multidisciplinary approach combining spectroscopy, microscopy and flow cytometry was applied. Time-Resolved Laser Induced Fluorescence Spectroscopy (TRLFS) analyses demonstrated that the biosorption of Cm(III) is a reversible and pH-dependent process for R. mucilaginosa BII-R8 cells. Two Cm(III)-R. mucilaginosa BII-R8 species were identified having emission maxima at 599.6 and 601.5 nm. They were assigned to Cm(III) species bound to phosphoryl and carboxyl sites from the yeast cell, respectively. Phosphate groups were involved in the sorption of this actinide, as demonstrated by the Eu(III)-phosphate accumulates at the cell membrane shown by microscopy. In addition, cell viability and metabolic potential were assessed to determine the negative effect of Eu(III) in the yeast cells. The results obtained in this work showed that the interaction of Cm(III) with the yeast R. mucilaginosa BII-R8 cells at circumneutral and alkaline pH values will make this radionuclide more mobile to reach the biosphere. Therefore, geochemical conditions in the bentonite engineering barrier need to be carefully adjusted for the safe deep geological disposal of radioactive wastes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Silver-impregnated zeolite (AgIZ) has been used for removing radioiodine from contaminated groundwater and nuclear waste streams and the worldwide inventory of such secondary waste is rapidly increasing. The objective of this study was to 1) quantify the effectiveness of two grout waste forms for disposing of the used AgIZ, and 2) determine the I speciation leached from AgIZ encapsulated in grout. A 60-day kinetics batch experiment demonstrated that AgIZ encapsulated in slag-free grout was extremely effective at immobilizing I and Ag, a potential non-radioactive carcinogen. However, AgIZ encapsulated in slag-containing grout, the most common type of grout used for low-level radioactive waste disposal, was entirely ineffective at immobilizing I. While the slag-free grout with AgIZ released only 3.3 μg/L I total into the contact solution, the slag-containing grout released 19,269 μg/L I total . Based on thermodynamic calculations, the strongly reducing conditions of the slag-containing system (Eh was -392 mV) promoted the reductive dissolution of the AgI, forming Ag 0 (aq) and releasing iodide (I - ) into the aqueous phase. The slag-free grout system was maintained under more oxidizing conditions (Eh was 439 mV) and a minimal amount of I was released from the grout. In both grout systems, the aqueous I, originally added to the AgZ as iodide, was composed primarily of iodide and org-I, and essentially no iodate was detected. More organo-I was detected in the slag-free than the slag-containing grout system because the high redox potential of the former system was more conducive to the formation of oxidized I species, such as I 2 , which may be intermediates in the covalent bonding of I with organic C in grout. Iodine K-edge XANES analysis indicated that I existed exclusively as silver iodide in both AgIZ-grout samples. Together, these results indicate that subsurface grout disposal of AgIZ waste should be done under oxidizing conditions and that radioiodide released from AgIZ can undergo speciation transformations that have important implications on subsequent mobility and estimated risk., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The contamination of the environment by U may affect plant life and consequently may have an impact on animal and human health. The present work describes U(VI) sequestration by Acidovorax facilis using a multidisciplinary approach combining wet chemistry, transmission electron microscopy, and spectroscopy methods (e.g. cryo-time resolved laser-induced fluorescence spectroscopy, extended X-ray absorption fine structure spectroscopy, and in-situ attenuated total reflection Fourier transform infrared spectroscopy). This bacterial strain is widely distributed in nature including U-contaminated sites. In kinetic batch experiments cells of A. facilis were contacted for 5 min to 48 h with 0.1 mM U(VI). The results show that the local coordination of U species associated with the cells depends upon time contact. U is bound mainly to phosphate groups of lipopolysaccharide (LPS) at the outer membrane within the first hour. And, that both, phosphoryl and carboxyl functionality groups of LPS and peptidoglycan of A. facilis cells may effectuate the removal of high U amounts from solution at 24-48 h of incubation. It is clearly demonstrated that A. facilis may play an important role in predicting the transport behaviour of U in the environment and that the results will contribute to the improvement of bioremediation methods of U-contaminated sites., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Highly efficient removal of metal ion pollutants, such as toxic and nuclear waste-related metal ions, remains a serious task from the biological and environmental standpoint because of their harmful effects on human health and the environment. Recently, highly porous metal-organic frameworks (MOFs), with excellent chemical stability and abundant functional groups, have represented a new addition to the area of capturing various types of hazardous metal ion pollutants. This review focuses on recent progress in reported MOFs and MOF-based composites as superior adsorbents for the efficient removal of toxic and nuclear waste-related metal ions. Aspects related to the interaction mechanisms between metal ions and MOF-based materials are systematically summarized, including macroscopic batch experiments, microscopic spectroscopy analysis, and theoretical calculations. The adsorption properties of various MOF-based materials are assessed and compared with those of other widely used adsorbents. Finally, we propose our personal insights into future research opportunities and challenges in the hope of stimulating more researchers to engage in this new field of MOF-based materials for environmental pollution management.

The ubiquitous nature of microbes has made them the pioneers in radionuclides adsorption and transport. In this study, the radiation resistance and nuclide biosorption capacity of microbes isolated from the Lanyu low-level radioactive waste (LLRW) repository in Taiwan was assessed, the evaluation of the possibility of using the isolated strain as biosorbents for (60)Co and Co (II) from contaminated aqueous solution and the potential impact on radionuclides release. The microbial content of solidified waste and broken fragments of containers at the Lanyu LLRW repository reached 10(5) CFU/g. Two yeast strains, Candida guilliermondii (CT1) and Rhodotorula calyptogenae (RT1) were isolated. The radiation dose necessary to reduce the microbial count by one log cycle of CT1 and RT1 was 2.1 and 0.8 kGy, respectively. Both CT1 and RT1 can grow under a radiation field with dose rate of 6.8 Gy/h, about 100 times higher than that on the surface of the LLRW container in Lanyu repository. CT1 and RT1 had the maximum (60)Co biosorption efficiency of 99.7 ± 0.1% and 98.3 ± 0.2%, respectively in (60)Co aqueous solution (700 Bq/mL), and the (60)Co could stably retained for more than 30 days in CT 1. Nearly all of the Co was absorbed and reached equilibrium within 1 h by CT1 and RT1 in the 10 μg/g Co (II) aqueous solution. Biosorption efficiency test showed almost all of the Co (II) was adsorbed by CT1 in 20 μg/g Co (II) aqueous solution, the efficiency of biosorption by RT1 in 10 μg/g of Co (II) was lower. The maximum Co (II) sorption capacity of CT1 and RT1 was 5324.0 ± 349.0 μg/g (dry wt) and 3737.6 ± 86.5 μg/g (dry wt), respectively, in the 20 μg/g Co (II) aqueous solution. Experimental results show that microbial activity was high in the Lanyu LLRW repository in Taiwan. Two isolated yeast strains, CT1 and RT1 have high potential for use as biosorbents for (60)Co and Co (II) from contaminated aqueous solution, on the other hand, but may have the impact on radionuclides release from LLRW repository., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Bacteria are key players in the processes that govern fate and transport of contaminants. The uranium release from Na and Ca-autunite by Arthrobacter oxydans strain G968 was evaluated in the presence of bicarbonate ions. This bacterium was previously isolated from Hanford Site soil and in earlier prescreening tests demonstrated low tolerance to U(VI) toxicity compared to other A. oxydans isolates. Experiments were conducted using glass serum bottles as mixed bioreactors and sterile 6-well cell culture plates with inserts separating bacteria cells from mineral solids. Reactors containing phosphorus-limiting media were amended with bicarbonate ranging between 0 and 10 mM and meta-autunite solids to provide a U(VI) concentration of 4.4 mmol/L. Results showed that in the presence of bicarbonate, A. oxydans G968 was able to enhance the release of U(VI) from Na and Ca autunite at the same capacity as other A. oxydans isolates with relatively high tolerance to U(VI). The effect of bacterial strains on autunite dissolution decreases as the concentration of bicarbonate increases. The results illustrate that direct interaction between the bacteria and the mineral is not necessary to result in U(VI) biorelease from autunite. The formation of secondary calcium-phosphate mineral phases on the surface of the mineral during the dissolution can ultimately reduce the natural autunite mineral contact area, which bacterial cells can access. This thereby reduces the concentration of uranium released into the solution. This study provides a better understanding of the interactions between meta-autunite and microbes in conditions mimicking arid and semiarid subsurface environments of western U.S., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Naturally available low cost materials have gained importance as effective alternative to conventional sorbents for the removal of metal ions from water. The present study describes the use of black hair waste as a sorbent for the removal of uranium ions from an aqueous medium. Alkali treatment of the biomass resulted in a significant increase in its uptake capacity. The optimum pH and contact time for uranium removal were 4.5 and 2 h respectively. It was observed that the experimental data fits well in Ho's pseudo-second order kinetic model. Binding of uranium to the biomass was confirmed using FT-IR spectroscopy. Thus, the present study could demonstrate the utility of human black hair to remove uranium from aqueous medium., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The objectives of this study were to examine (1) the distribution of U and Th in dolomitic gravel fill and shale saprolite, and (2) the removal of uranium from acidic groundwater by dolomitic gravel through precipitation with amorphous basaluminite at the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) field site west of the Oak Ridge Y-12 National Security Complex in East Tennessee. Media reactivity and sustainability are a technical concern with the deployment of any subsurface reactive media. Because the gravel was placed in the subsurface and exposed to contaminated groundwater for over 20 years, it provided a unique opportunity to study the solid and water phase geochemical conditions within the media after this length of exposure. This study illustrates that dolomite gravel can remove U from acidic contaminated groundwater with high levels of Al(3+), Ca(2+), NO(3-), and SO4(2-) over the long term. As the groundwater flows through high pH carbonate gravel, U containing amorphous basaluminite precipitates as the pH increases. This is due to an increase in groundwater pH from 3.2 to ∼6.5 as it comes in contact with the gravel. Therefore, carbonate gravel could be considered as a possible treatment medium for removal and sequestration of U and other pH sensitive metals from acidic contaminated groundwater. Thorium concentrations are also high in the carbonate gravel. Thorium generally shows an inverse relationship with U from the surface down into the deeper saprolite. Barite precipitated in the shallow saprolite directly below the dolomitic gravel from barium present in the acidic contaminated groundwater., (Copyright © 2014 Elsevier B.V. All rights reserved.)