bluuebunny/crossref_metadata_2025_split huggingface dataset:
Technology and Equipment Based on Induction Melters with.Cold. Crucible for Reprocessing Active Metal Waste
Authors: Pastushkov V.G. , Molchanov A.V. , Serebryakov V.P. , Smelova T.V. , Shestoperov I.N. 
Published: May 2011

ABSTRACTThe operation and, particularly, the decommissioning of NPPs and radiochemical plants result in substantial arisings of radioactive metal waste (RAMW) having different activity levels (from 5×10−4 to ≍ 40 Ci/kg).This paper reviews the specific features of the technology and equipment used to melt RAMW in electric arc and induction furnaces with ceramic or cold crucibles. The experimentally determined and calculated data are given on the level to which RAMW is decontaminated from the main radionuclides as well as on the distribution of the latter in the products of melting (ingot, slag, gaseous phase).Special attention is focused on the process and the facility for the induction-slag melting of RAMW in furnaces equipped with cold crucibles. The work described is under way at SSC RF VNIINM to master the technology of melting simulated high activity level Zr-alloy and stainless steel waste.
Ion Exchange Behavior of the Febex Bentonite: 2. Batch Experiments and Geochemical Modeling
Authors: Delgado J. , Carretero P. , Juncosa R. , Samper J. , Huertas F.J. , De Cisneros C. Jiménez , Caballero E. , Huertas F. , Linares J. 
Published: May 2011

ABSTRACTIon exchange experiments have been performed with the FEBEX bentonite. Five grams of dry powder of this clay were put inside dialysis bags, which were located inside PFA reactors filled with 125 ml of water of a given chemical composition (Moody, Grimsel, and bentonitic-granitic type waters). The reactors containing the clay powder/water mixture were heated to different temperatures (from room temperature up to 80°C) along a time span ranging from 1 day to 1 year. Water was renewed according to a prescribed schedule but not the clay, which remained in place for the whole extent of each test. After each water renewal, major cations, silica, total inorganic carbon, and pH were analyzed. At the end of each test, the exchange complex and CEC of the bentonite were measured. These experiments have been modeled with a conveniently modified version of the EQ3/6 software package where ion exchange reactions were formulated as half reactions and added to its database. In general, model results are in fairly good agreement with experimental data, especially in the case of dissolved cations. Computed values of exchanged concentrations also match the measurements, although in some cases they deviate from them. The fact that the numerical results reproduce the observed patterns of exchange tests indicates that the adopted geochemical conceptual model is appropriate. Some features of the geochemical evolution of these tests also take place at the “mock-up” and “in situ” FEBEX tests.
The Effect of Pore Structural Factors on Diffusion in Compacted Sodium Bentonite
Authors: Sato Haruo 
Published: May 2011

ABSTRACTFour kinds of diffusion experiments; (1) through-diffusion (T-D) experiments for diffusion direction dependency to compacted direction, (2) in-diffusion (I-D) experiments for composition dependency of silica sand in bentonite, (3) I-D experiments for initial bentonite grain size dependency, and (4) I-D experiments for the effect of a single fracture developed in bentonite, were carried out using tritiated water (HTO) to evaluate the effect of pore structural factors on diffusion. For (1), effective diffusivities (De) in Na-bentonites, Kunigel-V1Ŵ and Kunipia-FŴ, were measured for densities of 1.0 and 1.5 Mg.m-3 in the axial and perpendicular directions to compacted one. Although De values in Kunigel-V1Ŵ for both directions were similar over the density, De values for perpendicular direction to compacted one in Kunipia-FŴ were higher than those for the same direction as compacted one. For (2), apparent diffusivities (Da) in Kunigel-V1Ŵ with silica sand were measured for densities of 0.8 to 1.8 Mg.m-3. No significant effect of the mixture of silica sand was found. For (3), Da values for densities of 0.8 to 1.8 Mg.m-3 were measured for a granulated Na-bentonite, OT-9607Ŵ. However, no effect of initial bentonite grain size was found. For (4), Da values in Kunigel-V1Ŵ, in which a single fracture was artificially reproduced and immersed in distilled water, were measured. No effect of the fracture on Da was found. Based on this, it may be said that the composition of smectite in bentonite affects the orientation property of clay particle and also affects diffusion. Furthermore, a penetrated fracture formed in bentonite is restored for a short while and does not affect diffusion.
Experimental Indications of Effects of Surface Deprotonation on Na-Bentonite Porewater Chemistry in a Geological Repository
Authors: Oda C. , Shibata M. , Yui M. 
Published: May 2011

ABSTRACTBentonite-water interaction was studied using a simple equilibrium model based on experimental measurements in order to describe bentonite porewater chemistry. Direct pH measurements for highly compacted bentonite and batch-type bentonite-water interaction experiments were performed under anaerobic conditions. In the direct pH measurements, resin particles doped with a pH indicator were sandwiched between a pair of bentonite columns immersed in a test solution. The experimental results showed that the solution compositions in equilibrium with bentonite depended on the bentonite to liquid ratio (B/L) and the initial solution composition. An equilibrium model assuming only fast equilibration processes between the bentonite minerals and the solution could be used to calculate the trends of pH and other ion concentrations with B/L. This study indicates that the surface deprotonation of smectite is a very important factor influencing the porewater chemistry in highly compacted bentonite.
Integrating Microbiology into the Drigg Post-Closure Radiological Safety Assessment
Authors: Beadle I. , Humphreys P. N. , Pettit C. , Small J. 
Published: May 2011

ABSTRACTBNFL owns and operates the UK's principal solid Low Level Radioactive Waste disposal site at Drigg in Cumbria, north west England. Drigg has been receiving waste since 1959 with approximately 900,000 m3of waste disposed of to date. Waste accepted for disposal at Drigg comes in a variety of forms including rubble, spoil, redundant equipment, scrap and process waste, and typically contains significant metallic and cellulosic components. The organic content of the waste means that microbial activity plays a significant role in the development of the repository environment. Consequently, microbial processes are integrated into many aspects of the Drigg Post-Closure Radiological Safety Assessment (PCRSA). This begins with the identification and screening of relevant features, events and processes, through supporting research, engineering designs and finally integration into radiological safety assessment modelling. This paper outlines how and where microbiology is integrated into the Drigg PCRSA and indicates areas of active research.
A Study on Conditions for Microbial Transport through Compacted Buffer Material
Authors: Fukunaga  , Honya M. , Yokoyama E. , Arai K. , Mine T. , Mihara M. , Senju T. 
Published: May 2011

ABSTRACTIn order to assess microbial transport through compacted buffer material consisting of bentonite and silica sand with a density of 1.2, 1.6 or 1.8 g/cm3, sterilized test pieces with the diameter of 50 mm and the depth of 25 mm were fed with bacteria, Escherichia coli. The bacteria freely diffused when the proportion of Na-bentonite was 20 wt% or that of Ca-bentonite was 50 wt%. Bacterial movement was less than 5 mm in three weeks when the proportion of Na-bentonite was 70-100 wt% or that of Ca-bentonite was 100 wt%. A high proportion of bentonite is essential to slow down microbial entrance to the surface of a nuclear-waste container.
Effects of Lichens on Uranium Migration
Authors: Kasama Takeshi , Murakami Takashi , Ohnuki Toshihiko , Purvis O. William 
Published: May 2011

ABSTRACTThe lichenTrapelia involutafrom uraniferous spoil heaps in Cornwall, England, growing directly on the secondary uranium minerals, metazeunerite and metatorbernite, was examined by field-emission scanning electron microscopy and transmission electron microscopy to assess the effect ofTrapeliaon uranium migration. We observed metazeunerite, sericite and scorodite as well as unidentified Fe-, Pb/As-, Fe/As-, Al/P-, Pb-bearing minerals concentrated in the lichen exciple and medulla. In addition, metazeunerite also occurred in the epithecium. The chemistries, sizes, and occurrences of the above minerals in the lichen suggest that fixation of U as well as Pb, As, Fe, and Al is dependent on lichen physiological processes. We suggestTrapeliaaccumulates these elements from groundwater and precipitates the above minerals within specific tissues. Our results indicate that some lichens retard uranium migration by accumulating uranium from groundwater and forming uranium-bearing minerals within their tissues.
Enthalpies of Formation of Gd2(Ti2-xZrx)O7 Pyrochlores
Authors: Helean K.B. , Begg B.D. , Navrotsky A. , Ebbinghaus B. , Weber W.J. , Ewing R.C. 
Published: May 2011

ABSTRACTA calorimetric investigation of the enthalpies of formation of Gd2(Ti2-xZrx)O7, where 0≤ × ≤ 2 is underway. All samples exhibit pyrochlore (Fd3m) peaks in their XRD patterns. However, where x=2 significant local disorder is observed in the Raman spectra. Preliminary data for the enthalpies of formation from the oxides in kJ/mol are: x=0, ΔHf = -113.4±2.7; x=0.5, ΔHf = -94.0±3.0; x=1.0, ΔHf = -74.2±4.9; x=1.5, ΔHf = -64.5±2.0; x=2, ΔHf = -52.2±4.8. Two additional samples, Gd1.80Zr2.15O7.00 (pyrochlore) and Gd2.15Zr1.87O7.00 (fluorite), were also studied. Their enthalpies of formation from the oxides in kJ/mole are -50.9±3.3 and -46.4±3.4 respectively. Replacing Ti with Zr, i.e. when x=2, destabilizes the pyrochlore in enthalpy by approximately 60 kJ/mol. The ΔHmix for the Gd2(Ti2-xZrx)O7 solid-solution series is positive and can be described by a regular solution formalism with an estimated interaction parameter, ŝ = +20 kJ/mol. The results of this study suggest that the pyrochlore to fluorite transition enthalpy in Gd2Zr2O7 is small, of the order of the configurational entropy contribution due to cation disorder at the transition temperature, TΔSconf. ≍ 10 kJ/mol.
SR 97: Post-Closure Safety for a KBS 3 Deep Repository for Spent Nuclear Fuel - Overview -
Authors: Hedin Allan , Kautsky Ulrik , Morén Lena , Selroos Jan-Olof , Sellin Patrik , Ström Anders , Papp Tönis 
Published: May 2011

ABSTRACTIn preparation for coming site investigations for siting of a deep repository for spent nuclear fuel, the Swedish Nuclear Fuel and Waste Management Company, SKB has carried out the long- term safety assessment SR 97, requested by the Swedish Government. The repository is of the KBS-3 type, where the fuel is placed in isolating copper canisters with a high-strength cast iron insert. The canisters are surrounded by bentonite clay in individual deposition holes at a depth of 500 m in granitic bedrock. Geological data are taken from three sites in Sweden to shed light on different conditions in Swedish granitic bedrock.The future evolution of the repository system is analyzed in the form of five scenarios. The first is a base scenario where the repository is postulated to be built entirely according to specifications and where present-day conditions in the surroundings, including climate, persist. The four other scenarios show the evolution if the repository contains a few initially defective canisters, in the event of climate change, in the event of earthquakes, and in the event of future inadvertent human intrusion.The principal conclusion of the assessment is that the prospects of building a safe deep repository for spent nuclear fuel in Swedish granitic bedrock are very good. The results of the assessment also serve as a basis for formulating requirements and preferences regarding the bedrock in site investigations, for designing a program for site investigations, for formulating functional requirements on the repository's barriers, and for prioritization of research.
SR 97: Hydromechanical Evolution in a Defective Canister
Authors: Sellin Patrik 
Published: May 2011

ABSTRACTThis paper describes the modelling of the hydromechanical evolution of a nuclear waste canister with an initial defect. The waste canister in the Swedish concept consists of a corrosion- resistant copper shell that covers a cast iron insert that provides mechanical strength.If there is an initial penetrating defect in the copper shell, water will be able to contact the insert. Ingress of water is a prerequisite for corrosion of the iron insert, which in turn gives rise to production of hydrogen gas. Water is also a prerequisite for corrosion of the fuel assembly's metal parts, fuel dissolution and radionuclide transport. Due to the fact that the corrosion processes both consume water and generate hydrogen, strong couplings exist between the chemical and the hydraulic evolution, which must therefore be described in a coupled context. Certain aspects of the mechanical evolution must also be dealt with in parallel with the hydrochemical processes.
Thermal Considerations in a Very Deep Borehole Nuclear Waste Repository for Synroc
Authors: Sizgek G.D. 
Published: May 2011

ABSTRACTA study of heat propagation in a very deep borehole radioactive waste repository for Synroc is presented. The deep borehole modeled for the high level wastes is hypothetically sited at approximately 4 km below ground level in a granite host rock. The high level waste containers are placed in the lower section of the borehole to within 1.5 km of the surface and backfilled. A geothermal gradient of 0.03°C/m is assumed. Transient temperature field calculations are carried out for both 20 wt% and 10 wt% high level radioactive waste (HLW) bearing Synroc, for cooling periods between reactor discharge and geological disposal varying from 5 years to 50 years. The temperatures in the borehole repository were found to be very sensitive to the surface cooling period as well as the waste loading. The initial heat input of the waste may be controlled by cooling in an interim storage until the total heat output is reduced to a suitably low level. Therefore, surface cooling of at least 15 years for 20 wt% HLW containing Synroc is necessary for the given deep bore hole configuration to avoid the centerline temperatures that might affect durability of Synroc if ground water obtained access to the waste form. On the other hand the corresponding minimum surface cooling period for 10 wt% HLW containing Synroc is predicted to be about 5 years to produce similar temperature profiles in the borehole to those of 20 wt% HLW bearing Synroc with a 15-year cooling period before disposal. A variation in the borehole diameter has also been performed to elucidate the sensitivity of the temperature field of the repository.
Progress in the Geomicrobiology of Radioactive Waste Disposal
Authors: West J. M. , McKinley I. G. 
Published: May 2011

ABSTRACTOver the past 20 years, radioactive waste microbiology has included a variety of analyses of disposal options for High Level (HLW) and Low/Intermediate Level (L/ILW) waste. Projects have covered a wide range of areas including: fundamental microbiology of geological formations; microbial tolerance to extreme conditions; biodegradation of repository materials and the interaction of radionuclides with microbes and their by-products. The work has included field sampling, laboratory studies, natural analogue investigations and development of mathematical models. Progress in the topic is considered by evaluating each part of the repository system in terms of microbial presence, possible microbial influence on the performance of the engineered and natural barriers, and how such influences can be quantified. From this perspective, priorities for future work in this area are identified.
Repository Design Optimization for Long-Lived ILW
Authors: McKinley I.G. , Kawamura H. , Neall F.B. , Ando K. 
Published: May 2011

ABSTRACTFrom the point of view of clear demonstration of long-term safety, some of the long-lived intermediate-level wastes (ILW) are probably the most challenging of all waste types. Repository concepts for such wastes are reviewed with respect to optimization of operational procedures, post-closure performance, ease of making the safety case and costs. In particular, the advantages of designs incorporating a hydraulic cage and partitioning of wastes with different properties are discussed.
Grimsel 2000 – Status of International Projects at the Grimsel Test Site (GTS)
Authors: Kickmaier W. , Alexander W. R. , Vomvoris S. , McKinley I.G. 
Published: May 2011

ABSTRACTDuring 17 years of cooperation, the Grimsel underground test site in the Swiss Alps has become established as a major center for study of the deep geological environment. The present Phase V of operation involves collaboration of 15 organizations from 9 countries.The 7 major projects currently running can be divided into 3 areas:- Confirmation of fundamental understanding and testing of models of processes identified to be significant in integrated performance assessment- Demonstration and optimization of site characterization technology- Demonstration of the technology for constructing and operating a deep repository in an efficient and quality assured manner.This sub-division of projects is somewhat simplistic as, wherever possible, large, long- running experiments are designed to achieve a number of goals. The paper will provide a summary of some projects running at Grimsel, an overview of the rationale behind the experimental concepts and a perspective on possible future work.
Alteration Features in Natural Zirconolite from Carbonatites
Authors: Williams C.T. , Bulakh A.G. , Gieré R. , Lumpkin G.R. , Mariano A.N. 
Published: May 2011

ABSTRACTIn nature, zirconolite occurs as an accessory mineral in many different rock types, but the majority of reported occurrences are from carbonatites (magmatic carbonates) of geological age varying from a few million years to 2 billion years old. Within these 19 carbonatite occurrences, of which 15 have been studied in some detail, zirconolite displays varying degrees of alteration in six samples. This alteration ranges from incipient minor effects to major corrosion, recrystallization and complete replacement by secondary phases. The degree of alteration broadly correlates with either the age, or actinide content of the zirconolite (or both), and thus the extent and degree of metamictization. Changes in zirconolite composition with alteration include an increase in hydration (H2O), Si, Ba and Pb (possibly radiogenic in origin), and a decrease primarily in Ca and Fe. Th can be remobilized, and of the rare earth elements (REE), there is evidence that the heavy-REE are mobilized more readily than the light-REE. Using backscattered electron images and electron microprobe analyses, this study documents and illustrates the range of alteration features observed in zirconolite from several carbonatites, in terms of both compositional and textural changes, and provides some physico-chemical information on the fluids responsible for the alteration.
Galena Crystallization and the Origin of Sulfur in the Oklo and Bangombé Natural Reactors: The Effects of a ca. 900 Ma Thermal Event
Authors: Zetterström Lena , Sunde Torbjörn 
Published: May 2011

ABSTRACTGalena in the ca. 1950 Ma old natural fossil fission reactors in Gabon crystallized sometime between 980 Ma and 750 Ma during a period of regional extension and the intrusion of a dolerite dyke swarm. The S isotopic composition of galena, containing radiogenic Pb from uraninite, gives information about the origin of the S. Results from ion microprobe analyses of galena from the reactor zones indicate that S mainly originates from the surrounding sediment. Galena in a thin, altered dolerite dyke also contains non-magmatic S. The presented data gives no positive evidence for the involvement of magmatic S during the ca. 900 Ma galena crystallisation, however, the possibility cannot be ruled out.
Sorption Behavior of Radionuclides on Calcium-Leached Mortar
Authors: Ashikawa Nobuo , Tajima Takatoshi , Saito Hiroshi , Fujiwara Ai 
Published: May 2011

ABSTRACTLow-level radioactive waste (LLRW) is disposed of by shallow land burial. Reinforced concrete is used as the radioactive waste repository. However, the concrete structure is in contact with water and will gradually degrade over an extended period of time due to leaching.It is important to investigate the interaction between radionuclides and degraded concrete in the safety assessment of nuclear waste disposal. The authors measured the distribution coefficients (Kd) of various radionuclides for calcium-leached mortars. The calcium-leached mortars were prepared by an accelerated leaching test for mortar based on the electrical potential gradient. These degraded conditions are similar to that of degraded concrete in contact with water for a long period of time. The degradation degree of calcium-leached mortar is evaluated by the CaO/SiO2molarratio (Ca/Si ratio) of calcium silicate hydrate (C-S-H).As a result, the relationship between Kd and the Ca/Si ratio in C-S-H can be roughly grouped into the following three types:1.137Cs and85Sr – Kd decreases with an increase in the Ca/Si ratio.2.95mTc and110mAg – There is no correlation between Kd and the Ca/Si ratio.3.14C,241Am and125I – Kd increases with an increase in the Ca/Si ratio.
The Labor Supply Consequences of Employment-Limiting Social Insurance Benefits: New Tests for Income Effects
Authors: Hyatt Henry R 
Published: May 2011

Abstract
Studies of moral hazard in employment-limiting social insurance programs such as Unemployment Insurance or Workers Compensation have demonstrated that higher benefits discourage work, emphasizing the price distortion inherent in benefit provision. Utilizing administrative data linking Workers’ Compensation claim records to wage records from an Unemployment Insurance payroll tax database, I explore a different explanation and implement tests for “income effects” that exploit the fact that claimants no longer experience a distorted price of non-employment after an employment-limiting benefit ends. A pair of legislative changes to a Workers’ Compensation benefit rate show little or no evidence of income effects and moderate evidence of income effects, respectively.
Small Fish Become Big Fish: Mergers in Stackelberg Markets Revisited
Authors: Brito Duarte , Catalão-Lopes Margarida 
Published: May 2011

Abstract
This paper analyzes, under convex costs, the price effects of mergers involving two Stackelberg followers that together become a leader and revisits the “merger paradox” and the insiders' dilemma. Contrary to what might be expected, prices are more likely to increase with cost convexity than with linear costs. Also, the incentive to free-ride may reappear.