bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immobilization Index of Liquid LLW in Cementitious Grouts
Authors: Sahu Sadananda , Diamond Sidney 
Published: April 2011

AbstractThe ability of grouts formulated from mixtures of cementitious materials and attapulgite clay to immobilize various chemical species in the projected off-gas waste stream from vitrification of Hanford low level tank wastes was studied. Three different solid blends were evaluated, with cement :fly ash : slag clay weight ratios of 3:3:3:1, 3:0:6:1, and 0:0:9:1. The blended solids were mixed with a simulated low level liquid waste solution containing Na+, NO2-, NO3-, PO43- and OH- ions, in the proportion of 1 liter of solution to 1 kg of solid blend, and were cured either at 22°C (room temperature), 50°C or 90°C. Pore solutions were expressed at various ages and were analyzed to determine the reductions in concentrations of the individual ionic species. The results were expressed in the form of immobilization index (I) calculated for each species. The immobilization indices for Na+ (I Na+ ) and for OH- (IOH-)were similar in each case, and were found to be highest when only slag and clay was present (blend 0:0:9:1). The immobilization index for phosphate, , was 1 in all cases, i.e. phosphate was completely removed from solution. On the other hand removal of NO2- and NO3- ions was generally ineffective.
Influence of the Titanium Dioxide Addition in Matrix Formulation on the Radwaste-Mortar Matrix Characteristics
Authors: Perić Aleksandar D. 
Published: April 2011

AbstractThe rutile form of titanium dioxide (TiO2) was added to mortar matrix preparations with the objective to improve the mechanical and physico-chemical characteristics of the radwaste-mortar matrix mixtures, in particular the leach-rate of the immobilized radionuclide. The final solidified radwaste form was made with high water-to-cement ratio (0.36) for easy leaching of the immobilized radionuclide, 37Cs. TiO2was added to the mortar formulation, replacing the appropriate amount of cement, in the amounts of 1,2,5,8 and 10 weight percents of total cement weight. In the highly basic environment of the mortar (pH ≅ 12), the titanium will form a HTiO-type membrane, which is semi-permeable and selective for the cations like Cs+ in the pH range above 5.5. Only the rutile form of TiO2was observed in the prospected radwastemortar mixture samples, using X-ray Fluorescence Spectrometry. Nevertheless, 137Cs leach-rate for the matrix formulations prepared with TiO2 was notably lower than the normally prepared (TiO2 free) samples. Furthermore, the mechanical strength of the samples prepared with TiO2 was higher than that of the TiO 2-free samples, and the correlation between the mechanical strength and TiO2 content appears to be exponential over the composition range explored here. Improvement of the physico-chemical properties of the titanium prepared formulations, is a topic of further investigations.
Electronic Structure Calculations of Calcium Silicate Hydrates
Authors: Sterne P. A. , Meike A. 
Published: April 2011

AbstractMany phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25°C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, we are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO3) and xonotlite (Ca6Si6O17(OH)2), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1–1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases.
A Procedure to Evaluate the Potential for Microbially Influenced Degradation of Cement-Solidified Low-Level Radioactive Waste Forms
Authors: Rogers R. D. , Hamilton M. A. , Veeh R. H. , Mcconnell J. W. 
Published: April 2011

AbstractBecause of its apparent structural integrity, cement has been widely used in the United States as a binder to solidify Class B and C low-level radioactive waste (LLW). However, the resulting cement preparations are susceptible to failure due to the actions of stress and environment. An environmentally mediated process that could affect cement stability is the action of naturally occurring microorganisms. The U.S. Nuclear Regulatory Commission (NRC), recognizing this eventuality, stated in their Technical Position on Waste Form, Revision 1, that the effects of microbial action on waste form integrity must be addressed. This paper provides recent results from a program that examined the effects of microbially influenced degradation (MID) on cement-solidified LLW. Data are provided which were obtained during the development of an evaluation method using acid-producing bacteria. Results presented here are from work with one type of these bacteria, the sulfur-oxidizingThiobacillus. Commercially prepared, cement-solidified, low-level radioactive waste form samples made from power reactor wastes were evaluated using a new biodegradation test developed for the NRC. Testing demonstrated that MID has the potential to severely compromise the structural integrity and nuclide retentiveness of ion-exchange resin and evaporator-bottoms wastes that have been solidified with cement. It was found that the waste form specimens physically deteriorated after 60 days of exposure to the thiobacilli. Also, the data show that significant amounts of Cs-137, Cs-134, Co-60, C-14, Tc-99, and Sr-90 contained in the waste forms were leached in the presence ofThiobacillus.
Modelling the Long-Term Chemical Evolution of Cement-Groundwater Systems
Authors: Neall F. B. 
Published: April 2011

AbstractThe importance of the large volumes of cement and concrete in the planned Swiss L/ILW repository in influencing the chemical environment of the repository and the sorption behaviour of the radionuclides has lead to an interest the long-term evolution of cement-groundwater systems for safety assessment purposes.A model is presented which simulates the leaching of a column hydrated cement/concrete with fresh groundwater, using a sequential mixing tank approach. The chemical model includes the incongruent dissolution of the CSH-gel phase and reaction of three other cement phases which make up over 90 wt. % of the hydrated cement paste. The model takes account of porosity changes due to dissolution and precipitation. Different concrete compositions can be included in the column in order to represent, for example, a section through a repository cavern. The model can be run as a 1-D flow-through system or as a quasi-1-D system in which flow in any segment is proportional to porosity. Although the model does not include the sophisticated transport models of currently available coupled codes, it does allow the possibility of assessing the duration of high pH conditions within the repository and the influence of different concrete/cement types or different waste type/loading as a first stage to determining long-term transport of radionuclides from the near field.
Excess Pu Disposition in Zirconolite-Rich Synroc Containing Nepheline
Authors: Vance E. R. , Hart K. P. , Day R. A. , Begg B. D. , Angel P. J. , Loi E. , Weir J. , Oversby V. M. 
Published: April 2011

AbstractA titanate Synroc ceramic for the immobilization of Pu-bearing waste was designed to consist of 70 wt% zirconolite (CaZrTi2O7) + 15 wt% nepheline (NaAlSiO4) + 15 wt% rutile (TiO2). It contained 10 wt% of Pu plus 6 wt% of Gd as a neutron poison. The material was made by our standard sol-gel route, using a mixture of alkoxides and nitrates, followed by stirdrying and calcination. It was fabricated by hot-pressing at 1150–1250°C/20 MPa for 2 hours in a collapsible metal bellows. Though zirconolite was the majority phase, ∼20 wt% of perovskite also formed. Some of the Na, intended for nepheline, partitioned into the titanate phases. 84-day differential total leach rates of Pu were in the order of 10−5 g/m2/d at 90 and 200°C. Companion ceramics using molar substitution of Ce for Pu confirmed the idea that Ce is a good simulant of Pu from a solid state chemical view, but that there are limitations in terms of leach rate parallels.
Models and Strategies for Blending Nuclear Wastes to Minimize Immobilized Waste Volume
Authors: Hoza M. 
Published: April 2011

AbstractHanford tank waste will be separated into high-level and low-level portions; each portion will then be vitrified to produce a stable glass form for disposal. Because of the wide variability in the tank waste compositions, blending is being considered as a way to reduce the number of distinct compositions that must be vitrified and to minimize the resultant volume of vitrified waste.This paper discusses several approaches to blending and models developed to formulate blends for each approach. The models produce optimized blends which minimize the volume of glass required such that all composition and property constraints on the glass are satisfied. The paper will discuss several blending strategies, and will provide the results of calculations comparing the approaches and strategies. Finally, an overall strategy for retrieving, blending, and vitrifying Hanford tank waste will be briefly discussed.Results of the calculations for high-level waste show that an effective blending strategy can greatly reduce the volume of glass required to immobilize the waste.
Selective Extraction of Cs and Co from Liquid Radioactive Waste
Authors: Karlin Y. V. , Prozorov L. B. , Chuikov V. Y. , Kropotov V. N. 
Published: April 2011

AbstractThis paper demonstrates that selective sorbents (in particular, ferri-ferrocyanide nickel) can be regenerated electrochemically. It is shown that the degree of sorbent regeneration and the ion permselectivity of the process depends on the electric current density, the apparatus design and the scheme of the extraction process.
Effect of Microbial Action on the Corrosion Potential of Austenitic Alloy Containers for High-Level Nuclear Waste
Authors: Angell P. , Dunn D. S. , Cragnolino G. A. 
Published: April 2011

AbstractThe safe disposal of high-level nuclear waste (HLW) entails the ability to ensure the integrity of waste containers for prolonged time periods. It is generally accepted that under certain conditions, microbial action may change local benign environments to those in which localized corrosion can be actively promoted. The use of repassivation potential (Erp) in relation to the value of the corrosion potential (Ecorr) has been proposed as a means of assessing the propensity of a metallic material to localized corrosion. Microbial activity is known to influence Ecorr however, the precise mechanism is unresolved. Shewanella putrefaciens, a bacteria with many of the characteristics of sulfate-reducing bacteria (SRB), are being grown under controlled conditions on 316L stainless steel (SS) surfaces to understand the relationship between Ecorr and metabolic activity. It has been observed that the growth of the bacteria under aerobic conditions, without the production of metabolic sulfide, leads to only minor variation in Ecorr. These changes possibly correlate to the periods of active bacterial growth.
Modelling the Consumption of Oxygen by Container Corrosion and Reaction with Fe(II)
Authors: Kolář M. , King F. 
Published: April 2011

AbstractA model is described that predicts the rate of O2 consumption in a sealed nuclear fuel waste disposal vault as a result of container corrosion, reaction with biotite and the oxidation of organics and other oxidizable impurities in the clay. The most important reactions leading to the consumption of O2 for Cu containers in a conceptual Canadian disposal vault are container corrosion, the oxidation of dissolved Cu(I) and the oxidation of organics and other impurities in the clay. Consumption of O2 by the oxidation of dissolved Fe(II) from biotite is significant in backfill materials containing crushed granite and in the rock itself. The O2 initially trapped in the disposal vault is predicted to be consumed in between 50 and 670 a.
A Numerical Model for the Corrosion of Copper Nuclear Fuel Waste Containers
Authors: King F. , Kolář M. 
Published: April 2011

AbstractA model is presented for the prediction of the long-term corrosion behaviour of Cu nuclear fuel waste containers. The model is based on a kinetic description of the processes involved in the uniform corrosion of Cu in a conceptual Canadian disposal vault. The 1-dimensional, multilayer model accounts for mass-transport, electrochemical and chemical processes and predicts the spatial and temporal variations of the concentrations of various dissolved, precipitated and adsorbed species, as well as the time dependence of the corrosion rate and the corrosion potential (ECORR). The variation of [O2], [Cu(II)] and ECORR with time can also be used to predict the maximum period over which localized corrosion processes, such as pitting or stress corrosion, may occur. Predictions from the model suggest that 25-mm-thick Cu containers will not fail due to uniform corrosion or pitting in periods <106 a.
Effects of Anionic Species on the Polarization Behavior of Copper for Waste Package Material in Artificial Ground Water
Authors: Imai Hachiro , Fukuda Takanori , Akashi Masatsune 
Published: April 2011

AbstractThe effects of HCO3, Cl, and SO42- on copper as a candidate material for overpacking for geological disposal of high level radioactive wastes are studied at 303 K in dissolved oxygen(DO)- controlled, ground-water simulating aqueous solutions by using a cyclic polarization curve method.Two types of polarization curve were determined: Type A in which free corrosion proceeds in the active dissolution mode, and Type P in which passivation takes place in a potential domain characterized by a potential that corresponds to Eb, the potential at which the passivated film is broken. Polarization dependence on DO was also determined: when only HCO3 is present, a Type A curve results for DO < 0.5 ppm when HCO3 = 10 – 300 ppm, transiting to a Type P curve when HCO3 > 3,000 ppm; when DO < 15ppm, however, a Type P results for HCO3 ≤ 10 ppm; when either Cl− or SO42- coexists with HCO3, HCO3 promotes passivation while Cl- and SO42- promote active dissolution, the influence of Cl− being greater than that of HO42- if HCO3 content is constant. The presence of either CI or SO42 over 100 ppm makes the curve Type A irrespective of DO, both species shifting Eb toward the less noble direction.The constant potential test shows that the passivated film of copper is easily broken if Cl− is present.
Neptunium(V) Sorption Behavior on Clinoptilolite, Quartz and Montmorillonite
Authors: Bertetti F. P. , Pabalan R. T. , Turner D. R. , Almendarez M. G. 
Published: April 2011

AbstractPerformance assessment models have identified237Np as a radionuclide of concern in meeting release limits established for the geologic disposal of high-level nuclear waste at the proposed repository at Yucca Mountain, Nevada. In this study, quartz, clinoptilolite, and montmorillonite, which are minerals representative of phases that occur both in the rock matrix and as fracture coatings at Yucca Mountain, were reacted with237Np-bearing solutions to characterize the sorption behavior of Np(V) on these minerals.Batch experiments were conducted over a wide range of conditions in which pH of solution, surface loading, sorbent surface area, initial concentration of Np(V), and partial pressure of CO2were varied. Initial Np(V) concentrations were between 1 × 10-7and 1- 10-6M in electrolyte solutions of 0.1 or 0.01 M NaNO3. The oxidation state of Np in solution was verified with NIR spectroscopy and by solvent extraction. Prior to the start of experiments, minerals were pretreated to eliminate impurities, and the clinoptilolite and montmorillonite were converted to Na-form by ion exchange with NaCI solutions.Results indicate that, for all three minerals, Np(V) sorption begins at pH values coincident with the start of hydrolysis in solution (-7). For solutions undersaturated with respect to atmospheric CO2, sorption increases continuously with increasing pH. Under equilibrium with atmospheric CO2, Np(V) sorption is important in the pH range (7–9.5) where NpO2(OH)°(aq) is significant, whereas sorption is inhibited at higher pH where neptunyl carbonate complexes are the predominant species.
SNL-1, a Highly Selective Inorganic Crystalline Ion Exchange Material for Sr2+ in Acidic Solutions
Authors: Nenoff T. M. , Thoma S. G. , Miller J. E. , Trudell D. E. 
Published: April 2011

AbstractA new inorganic ion exchange material, called SNL-1, has been prepared at Sandia National Laboratories. Developmental samples of SNL-1 have been determined to have high selectivity for the adsorption of Sr from highly acidic solutions (1 M HNO3). This paper presents results obtained for the material in batch ion exchange tests conducted at various solution pH values and in the presence of a number of competing cations. Results from a continuous flow column ion exchange experiment are also presented.
Applications of in Situ Cosmogenic Nuclides in the Geologic Site Characterization of Yucca Mountain, Nevada
Authors: Gosse J. C. , Harrington C. D. , Whitney J. W. 
Published: April 2011

AbstractThe gradual buildup of rare isotopes from interactions between cosmic rays and atoms in an exposed rock provides a new method of directly determining the exposure age of rock surfaces. The cosmogenic nuclide method can also provide constraints on erosion rates and the length of time surface exposure was interrupted by burial. Numerous successful applications of the technique have been imperative to the complete surface geologic characterization of Yucca Mountain, Nevada, a potential high level nuclear waste repository. The 10Be exposure age of Black Cone lava, within a ten mile radius of the proposed repository site, is 840 ± 210 kyr (in agreement with previous K/Ar dates of 1.0 ± 0.1 Ma). Rates of erosion of the tuff bedrock (< 0.4 cm/kyr from 7 10Be measurements) and of hillslope colluvium (∼ 0.5 cm/kyr from 10Be dates on boulder deposits) preclude denudation of the mountain as a concern. Neotectonic concerns (rate of slip and timing of last significant movement along faults) are also being addressed with in situ 14C and 10Be measurements on scarp surfaces and on fault-dissected landforms where no surficial expression of the fault is preserved.
The Yucca Mountain Standard: Proposals for Leniency
Authors: Pigford T. H. 
Published: April 2011

AbstractThe proposed geologic repository at Yucca Mountain, Nevada, for spent nuclear fuel and other highly radioactive waste needs an official standard to protect the public from release of radioactivity. Standards proposed by the U.S. Congress, the nuclear industry (NEI), the Electric Power Research Institute (EPRI), the Department of Energy (DOE), and the TYMS Committee of the National Research Council (NRC) are reviewed. Each of these proposals would introduce a degree of leniency not heretofore experienced in radiation protection. No adequate scientific justification is presented. Some scientifically invalid proposals are said to be justified on the grounds of policy. Most leading industrial nations are designing geologic repositories to meet the traditional criteria for safety and for protecting public health, including quantitative calculations of doses for the periods when significant doses can occur, rather than stopping calculations at 10,000 years as many in the U.S. would have us do. There is no evidence that they are seriously seeking more lenient standards for public health protection. The U.S. has the resources and skills to protect future people from our waste with the same care that we now protect the public from radiation. We should assert our will to do so. The Yucca Mountain project will be seriously damaged if it is directed to depart from the traditional conservative criteria for determining safety and protection of public health, criteria that are adopted in other countries working on geologic disposal.
ElectroluminesCence Behavior in Polymer Blend of Two Luminescent Polymers
Authors: Zyung Taehyoung , kim Jang-Joo , kang In-Nam , hwang Do-Hoon , Shim Hongku 
Published: April 2011

ABSTRACTWe report the electroluminescence behaviour of the devices made with the polymer blend of two emissible polymers, poly(2-methoxy,5-(2′ethyl-hexoxy)-1,4-phenylene vinylene)(MEHPPV) and poly[ 1,3-propanedioxy- 1,4-phenylene- 1,2-ethenylene-(2,5-bis(trimethylsilyl)- 1,4- phenylene)-l,2-ethenylene-l,4-phenylene](B-polymer) luminescing at 580 nm and 480 nm respectively. The quantum efficiency increases with the composition ratio of B-polymer by two order of magnitude of that of MEH-PPV. Luminescence behaviour of the blend system was explained by hole blocking, exciton transfer behavior of the matrix polymer (B-polymer) and efficient confinement of the injected carriers in MEH-PPV.
Synthesis And Properties Of Crosslinkable Phenylacetylene Donor-Acceptor Molecules
Authors: Spilman G. E. , Jiang T. , Lu Q. , Martin D. C. 
Published: April 2011

ABSTRACTBased on our previous work using benzocyclobutene (BCB) moieties in extended-chain polymers [1], it was thought that the construction of unsymmetrical molecules around the BCB unit might result in thermally crosslinkable NLO-active materials. The feasibility of incorporating such a functional system in donor-acceptor molecules without disrupting processability is discussed and demonstrated. The synthesis, processing, and characterization of these molecules was investigated by thermogravimetry, differential scanning calorimetry, and optical microscopy using a specially designed hot stage which makes it possible to apply an inplane electric field at elevated temperatures. The ability to rapidly and irreversibly crosslink bulk films without the generation of volatile byproducts provides a novel method for sustaining poled optical properties by locking in the desired orientation. The anisotropy of the electrically poled melt and sustained birefringence after BCB crosslinking and cooling demonstrates the achievement of molecular alignment in these new materials.
The Quest For Molecule-Based Magnets
Authors: Miller Joel S. , Epstein Arthur J. 
Published: April 2011

ABSTRACTIn the past decade a new class of magnets possessing spins on organic species have been discovered and studied. These magnets can be fabricated at room temperature and may enable useful devices and/or processes. Herein we discuss several of the mechanisms that can enable the stabilization of magnetic ordering and also provide examples of molecule-based magnets.
Conducting Polymers with Molecular Recognition Elements:Design of Highly Sensitive Sensory Aterials
Authors: Swager Timothy M. , Marsella Michael J. , Zhou Qin , Newland Robert J. 
Published: April 2011

ABSTRACTA number of approaches to the design and synthesis of conducting polymer-based sensory materials are presented. To elicit a selective sensory response synthetic receptors have been integrated into the polymers such that binding of an analyte produces electronic, electrostatic, and/or structural perturbations. A key element is the use of assemblies of many receptors which are “wired in series” by a conjugated polymeric structure. It is demonstrated that this configuration produces an inherent sensitivity gain over single isolated receptor-based sensory molecules.