bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Reactor Decontamination Complexing Agents on Soil Adsorption of Metals
Authors: Serne R. J. , Lindenmeier C. W. , Cantrell K. J. , Owen A. T. 
Published: April 2011

AbstractThe effects of picolinate, an organic ligand used to decontaminate nuclear reactor cooling systems, in leachates generated from shallow-land burial (SLB) of low-level nuclear wastes (LLW) on soil adsorption was determnined. Using batch adsorption tests and varying the concentration of picolinate, the adsorption tendencies of two metals [Ni(II) and U(VI)] and the ligand were measured as a function of solution pH. We found that when total metal concentrations were fixed at 10−5M, picolinate at ligand-to-metal [L:M] ratios ≥10 did significantly reduce adsorption of Ni but even at a L:M ratio of 100 there was no effect on U(VI) adsorption. These results are compared with data on other metals in the presence of picolinate and for metal adsorption in the presence of EDTA. We conclude that picolinic acid is less of a threat than EDTA in waste leachates to reduce metal adsorption (increase mobility) and that picolinate concentrations must reach or exceed 10−4M for the most impacted metals (i.e., those that form the very strongest complexes with picolinate). There are no leachate data on these decontamination agents for the common burial technique (disposal of de-watered resins in high integrity containers) that can be used to evaluate potential hazards of these organo-radionuclide complexes.
79Se: Geochemical and Crystallo-Chemical Retardation Mechanisms
Authors: Chen Fanrong , Burns Peter C. , Ewing Rodney C. 
Published: April 2011

Abstract79Se is a long-lived (1.1×106 years) fission product which is chemically and radiologically toxic. Under Eh-pH conditions typical of oxidative alteration of spent nuclear fuel, selenite or selenate are the dominant aqueous species of selenium. Because of the high solubility of metalselenites and metal-selenates and the low adsorption of selenite and selenate aqueous species under alkaline conditions, selenium may be highly mobile. However, 79Se released from altered fuel may be immobilized by incorporation into secondary uranyl phases as low concentration impurities, and this may significantly reduce the mobility of selenium. Analysis and comparison of the known structures of uranyl phases indicate that (SeO3) may substitute for (SiO3OH) in structures with the uranophane anion-topology (α.-uranophane, sklodowskite, boltwoodite) which are expected to be the dominant alteration phases of UO2 in Si-rich groundwater. The structural similarity of guillemninite, Ba[(UO2)3 (SeO3)2O2](H2O) 3 to phurcalite, [(UO2)3(PO4)2O2](H2O)7, suggests that the substitution (SeO3)↔ (PO4) may occur in phurcalite. The close similarity between the sheets in the structures of rutherfordine and [(UO2)(SeO3)] implies that the substitution (SeO3) ↔ (CO3) can occur in rutherfordine. However, the substitutions: (SeO3) ↔ (SiO3OH) in soddyite and (SeO3) ↔ (PO4) in phosphuranylite may disrupt their structural connectivity and are unlikely to occur.
Fate of Neptunium in an Anaerobic, Ethanogenic Microcosm
Authors: Banaszak J. E. , Webb S. M. , Rittmann B. E. , Gaillard J.-F. , Reed D. T. 
Published: April 2011

AbstractNeptunium is found predominantly as Np(IV) in reducing environments, but as Np(V) in aerobic environments. Currently, it is not known how the interplay between biotic and abiotic processes affects Np redox speciation in the environment. To evaluate the effect of anaerobic microbial activity on the fate of Np in natural systems, Np(V) was added to a microcosm inoculated with anaerobic sediments from a metal-contaminated freshwater lake. The consortium included metal-reducing, sulfate-reducing, and methanogenic microorganisms, and acetate was supplied as the only exogenous substrate. Addition of more than 10−5M Np did not inhibit methane production. Total Np solubility in the active microcosm, as well as in sterilized control samples, decreased by nearly two orders of magnitude. A combination of analytical techniques, including VIS-NIR absorption spectroscopy and XANES, identified Np(IV) as the oxidation state associated with the sediments. The similar results from the active microcosm and the abiotic controls suggest that microbially produced Mn(II/III) and Fe(II) may serve as electron donors for Np reduction.
Investigation of Bacterial Transport in the Large-Block test, A Thermally Perturbed Block of Topopah Spring Tuff
Authors: Chen C.-I , Meike A. , Chuu Y.-J. , Sawvel A. , Lin W. 
Published: April 2011

AbstractTransport of bacteria is investigated as part of the Large-Block Test (LBT), a thermally perturbed block of Topopah Spring tuff. Two bacterial species,Bacillus subtilisandArthrobacter oxydans, were isolated from the Yucca Mountain tuff. Natural mutants that can grow under the simultaneous presence of the two antibiotics, streptomycin and rifampicin, were selected from these species by laboratory procedures, cultured, and injected into the five heater boreholes of the large block hours before heating was initiated. The temperature, as measured 5 cm above one of the heater boreholes, rose slowly over a matter of months to a maximum of 142°C and to 60°C at the top and the bottom of the block. Samples were collected from boreholes located approximately 5 ft below the injection points. Double-drug-resistant bacteria were found in the collection boreholes nine months after injection. Biochemical tests support the identification ofB. subtilisin the collection boreholes. Double-drug-resistant microbes also appeared in the heater boreholes where the temperature had been sustainably high throughout the test. The number of double-drugresistant bacteria that were identified in the collection boreholes increased with time until the heater was deactivated. Negative indications in the collection holes after the heater was deactivated support the supposition that these bacteria were the species that were injected. An apparent homogeneous distribution among the collection boreholes suggests no pattern to the migration of bacteria through the block. The relationship between bacterial migration and the movement of water is not yet understood. These observations indicate the possibility of rapid bacterial transport in a thermally perturbed geologic setting. The implications for colloid transport need to be reviewed.
Murataite-based ceramics for actinide waste immobilization
Authors: Stefanovsky S. V. , Yudintse S. V. , Nikonov B. S. , Omelianenko B. I. , Ptashkin A. G. 
Published: April 2011

AbstractStudying the Synroc, doped with a simulated HLW, we have found, along with conventional Synroc phases (zirconolite, perovskite, hollandite), an extra phase with a stoichiornetry (Ca, Mn, U, TR)4(U, TR, Zr, Ti) 2(AI, Ti)7O22. XRD and TEM study has shown this phase is related to a very rare mineral murataite. In the present work a ceramic based on murataite is studied. The ceramic samples in the system: Ca-Mn-Ti-Zr-U-Ce-AI-Fe-O were produced and examined in details using XRD, SEM/EDS, TEM, and optical microscopy. Total amount of actinide (U) and rare earth (Ce, Gd) elements in the murataite exceeds 20 wt%. Isomorphic substitution schemes in the structures of synthetic and natural murataites are discussed. High isomorphic capacity of the murataite structure towards actinides and REEs, flexibility of its composition, feasibility of synthesis by melting, including a cold crucible melting, and very high chemical durability under hydrothermal conditions make the murataite-based ceramics very promising for actinides and excess weapon Pu fixation.
Corrosion of K-3 Glass-contact refractory in sodium-rich aluminosilicate melts
Authors: Lu X. D. , Gan H. , Buechele A. C. , Pegg I. L. 
Published: April 2011

AbstractThe corrosion of the glass-contact refractory Monofrax K-3 in two sodium-rich aluminosilicate melts has been studied at 1208 and 1283°C using a modified ASTM procedure with constant agitation of the melt by air bubbling. The results for the monolithic refractory indicate a fast initial stage involving phase dissolution and transformation and a later “passivated” stage in which the surface of the refractory has been substantially modified. The composition of the stable spinel phase in the altered layer on monolithic coupons of K-3 is almost identical to the equilibrium composition bracketed by the dissolution of powdered K-3 into under-saturated melts on the one hand, and by crystallization of spinels from supersaturated melts on the other. The temperature and melt shear viscosity were found to have significant effects on the rates of K-3 dissolution and transformation.
Analysis of Coordination Polyhedra Symmetry in Pyrochlore and Zirconolite Structures
Authors: Troole A. Y. , Stefanovsky S. V. 
Published: April 2011

AbstractZirconolite and pyrochlore are considered as promising host phases for high level waste (HLW). However, correct information on substitution mechanisms, forms of dopants incorporation in their structures and distortions in coordination polyhedra is presently unavailable. To clarify these points we use the electron paramagnetic resonance (EPR). Pyrochlore and three of zirconolite polytypes: zirconolite-2M, zirconolite-3T, and zirconolite-30 are considered. Pyrochlore is the “parent” structure for zirconolite since any zirconolite variety is produced by means of distortion of the initial pyrochlore structure. Space groups of pyrochlore and basic polymorphous zirconolite varieties found from XRD and TEM data, as well as interatomic distances and angles, were taken from reference data. This allows the determination of the most probable sites for impurities, substitution mechanisms, and local symmetry of coordination polyhedra (initial). Ions chosen for EPR were Gd (III) as an analog of trivalent rare earth and actinide elements which are also occurred in HLW and Fe (III) as a typical corrosion product which occurs in all HLW. For Gd (III) a strong ligand field approximation is suggested, theoretical computation using perturbation theory in this approximation has been carried out. All the non-diagonal members plus magnetic field were chosen as perturbation and formulae for transition frequencies, estimations of fine structure and g-factors parameters in the given approximation have been obtained.
Americium-Curium Vitrification Process Development (U)
Authors: Fellinger A. P. , Baich M. A. , Hardy B. J. , Jannik G. T. , Jones T. M. , Marra J. E. , Miller C. B. , Miller D. H. , Peeler D. K. , Snyder T. K. , Stone M. E. , Witt D. C. 
Published: April 2011

AbstractThe successful demonstration of sequentially drying, calcining and vitrifying an oxalate slurry in the Drain Tube Test Stand (DTTS) vessel provided the process basis for testing on a larger scale in a cylindrical induction heated melter. A single processing issue, that of batch volume expansion, was encountered during the initial stages of testing. The increase in batch volume centered on a sintered frit cap and high temperature bubble formation. The formation of a sintered frit cap expansion was eliminated with the use of cullet. Volume expansions due to high temperature bubble formation (oxygen liberation from cerium reduction) were mitigated in the DTTS melter vessel through a vessel temperature profile that effectively separated the softening point of the glass cullet and the evolving oxygen from cerium reduction. An increased processing temperature of 1470°C and a two hour hold time to fine any remaining bubbles successfully reduced bubbles in the poured glass to an acceptable level. The success of the preliminary process demonstrations provided a workable process basis that was directly applicable to the newly installed Cylindrical Induction Melter (CIM) system, making the batch flowsheet the preferred option for vitrification of the americium-curium surrogate feed stream.
Corrosion of Aluminum-Uranium Alloys in Water Vapor at 200 °C
Authors: Lam Poh-Sang , Sindelar Robert L. , Barrett Kelli Y. 
Published: April 2011

AbstractSpecimens of aluminum-uranium alloys at 10 and 18 weight percent uranium were exposed to a saturated water vapor condition at 200 °C up to about 12 weeks and compared to previous results for aluminum 1100. The aluminum-uranium materials exhibited a range of initial corrosion rates and approached similar rates with the formation of a passive film of boehmite (Al2O3·H2O). The initial corrosion rates of the aluminum-uranium materials were one to four times higher than that for aluminum 1100. It is postulated that a micro-galvanic coupling between the large UA14 particles and the aluminum matrix has caused this difference. Sectioning the exposed specimens shows different characteristics of the oxide layers. In the oxide on the aluminum-10% uranium alloy (Al-10%U), small uranium aluminide particles can be seen in a boehmite matrix and do not seem to be corroded. The oxide film on the aluminum- 18% uranium alloy (Al-18%U) appears to have two distinct oxide layers. The outer layer has mass aggregates in a boehmite matrix, while the inner layer contains UA14 particles as in the case of Al-10%U.
Stochastic Modeling of Long-Term Waste Package Degradation Incorporating Expert Elicitation on Corrosion Processes
Authors: Lee J. H. , Mori K. G. , Longsine D. E. , Bullard B. E. 
Published: April 2011

AbstractThe Viability Assessment (VA) of the potential repository for high-level nuclear waste at Yucca Mountain, Nevada was completed [1]. In the VA design concept, a two-layer waste container provides the primary component of the engineered barrier system (EBS). The VA reference design specifies a 100-mm thick carbon steel as the outer barrier and a 20-mm thick Alloy 22 as the inner barrier. A stochastic simulation model was developed to analyze long-term performance of the waste package in the potential repository. The model was developed by incorporating the latest corrosion data and models for the candidate waste package materials and the information developed from the Waste Package Degradation Expert Elicitation (WPDEE) [2].The reference case results showed that only a small fraction of waste packages fail by localized corrosion (i.e., pit penetrations). The analysis also indicated the degradation mode that is most important to long-term waste package degradation is general corrosion (or passive dissolution) of the inner barrier under dripping conditions. However, the general corrosion rates for dripping conditions used in the analysis have a range over three to five orders of magnitude. This is due mainly to a lack of information on local chemical and electrochemical conditions on the inner barrier after the outer barrier breach. This paper discusses further the areas and issues that need improvement to reduce uncertainty in the waste package degradation analysis. It also discusses additional waste package degradation modes and associated processes that need to be included in the future analysis for the potential repository to enhance the confidence of the analysis.
Scientific Bases for Cladding Credit as a Barrier to Radionuclide Release at the Proposed Yucca Mountain Repository+
Authors: Ahn T. M. , Cragnolino G. A. , Chan K. S. , Sridhar N. 
Published: April 2011

AbstractThe performance of Zircaloy nuclear fuel cladding in the environment of the proposed Yucca Mountain (YM) high-level waste (HLW) repository is evaluated. Because the uniform aqueous corrosion/oxidation rate is extremely slow, this evaluation focuses on mechanical failure, localized corrosion, stress corrosion cracking (SCC), hydrogen embrittlement, and initial failure. Mechanical failure is expected to result from (1) disruptive events such as rockfalls from seismicity, faulting, and igneous activities, (2) creep, and (3) splitting by oxidation of the spent fuel (SF) matrix. Effects of chloride ions and radiolysis are evaluated in localized corrosion and SCC. Embrittlement can be caused by delayed-hydride cracking (DHC) and hydride reorientation. Among these cladding failure modes, rockfalls, other disruptive events and initial defects can be important to performance prior to the container failure by corrosion. Confirmatory tests are required to evaluate the susceptibility to splitting by secondary mineral formation, localized corrosion, SCC, and hydride reorientation. Reliable temperature calculations with backfilling are also required. After breach, cladding may still assure slow release of radionuclides through perforations because localized failures may limit the exposure of the SF matrix and may provide high mass-transfer resistance. Failures prior to the repository emplacement arising from reactor operation, pool storage, dry storage, and transportation are also considered.
Alternative Assessments of the Performance of the Yucca Mountain Candidate HLW Repository
Authors: Kessler J. H. , MCGuire R. K. , Vlasity J. A. , Klos R. A. 
Published: April 2011

AbstractThis paper summarizes some of the most recent total system performance assessment (TSPA) work supported by EPRI for the proposed repository at Yucca Mountain, Nevada. In Part I of the paper, (standard) TSPA analyses are presented. In Part II examples of two types of analyses that augment standard TSPAs are provided that suggest: (1) many components of the Yucca Mountain system contribute to overall hazard reduction; and (2) the biosphere dose conversions used, based on reasonably maximizing assumptions about future human behavior, provide a reasonable upper bound. These additional analyses should provide further confidence when considering more (standard) TSPA analyses.
The Modeler's Influence on Calculated Solubilities for Performance Assessments at the Äspö Hard-Rock Laboratory
Authors: Emrén A. T. , Arthur Randy , Glynn Pierre D. , McMurry Jude 
Published: April 2011

AbstractFour researchers were asked to provide independent modeled estimates of the solubility of a radionuclide solid phase, specifically Pu(OH)4, under five specified sets of conditions. The objectives of the study were to assess the variability in the results obtained and to determine the primary causes for this variability.In the exercise, modelers were supplied with the composition, pH and redox properties of the water and with a description of the mineralogy of the surrounding fracture system A standard thermodynamic data base was provided to all modelers. Each modeler was encouraged to use other data bases in addition to the standard data base and to try different approaches to solving the problem.In all, about fifty approaches were used, some of which included a large number of solubility calculations. For each of the five test cases, the calculated solubilities from different approaches covered several orders of magnitude. The variability resulting firom the use of different thermodynamic data bases was in most cases, far smaller than that resulting from the use of different approaches to solving the problem.
Effective Diffusivities of Iodine, Chlorine, and Carbon in Bentonite Buffer Material
Authors: Kato H. , Nakazawa T. , Ueta S. , Muroi M. , Yasutomi I. , Fujihara H. 
Published: April 2011

AbstractEffective diffusivities of iodine, chlorine, and carbon in mixtures of bentonite and sand were determined by measuring the effective diffusivities of common chemical compounds labeled with radioactive isotopes of these elements. For carbon, both inorganic and organic carbon compounds were used in order to consider the variety of chemical forms of carbon possible in a radioactive waste repository. The bentonite content and dry density of the bentonite–sand mixture were varied. Two chemically different aqueous solutions, representing concrete pore water and bentonite pore water, were used to represent different conditions that could affect diffusivity in bentonite buffer material in a hypothetical radioactive waste disposal situation.The effective diffusivities of iodine, chlorine, and carbon tended to decrease with increasing bentonite content and dry density of the mixture. In the presence of simulated concrete pore water, the effective diffusivities for iodine, chlorine, and carbon in the bentonite mixtures were not higher than those obtained when simulated bentonite pore water was used. Except for some organic compounds, the measured effective diffusivities were lower than that of tritiated water under the same experimental conditions. This was attributed primarily to exclusion of anions from the bentonite pores. The effective diffusivity of carbon depended on its chemical form. The effective diffusivity of the anionic forms of organic carbon tested (carboxylic acids ) was as low as that of inorganic anionic carbon.Measured effective diffusivities were compared with those calculated using a model based on electrical double layer theory. The theory was applied to calculate distributions of electrolyte ions and diffusing ions in the bentonite pores. The calculated effective diffusivities showed good agreement with the measured values.
The Channel Network Model and Field Applications
Authors: Khademi B. , Moreno L. , Neretnieks I. 
Published: April 2011

AbstractThe Channel Network model describes the fluid flow and solute transport in fractured media. The model is based on field observations, which indicate that flow and transport take place in a threedimensional network of connected channels. The channels are generated in the model from observed stochastic distributions and solute transport is modelled taking into account advection and rock interactions, such as matrix diffusion and sorption within the rock. The most important site-specific data for the Channel Network model are the conductance distribution of the channels and the flow-wetted surface. The latter is the surface area of the rock in contact with the flowing water. These parameters may be estimated from hydraulic measurements. For the Äspö site, several borehole data sets are available, where a packer distance of 3 metres was used. Numerical experiments were performed in order to study the uncertainties in the determination of the flowwetted surface and conductance distribution. Synthetic data were generated along a borehole and hydraulic tests with different packer distances were simulated.The model has previously been used to study the Long-term Pumping and Tracer Test (LPT2) carried out in the Äspö Hard Rock Laboratory (HRL) in Sweden, where the distance travelled by the tracers was of the order hundreds of metres. Recently, the model has been used to simulate the tracer tests performed in the TRUE experiment at HRL, with travel distance of the order of tens of metres. Several tracer tests with non-sorbing and sorbing species have been performed.