bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Level Waste (HLW) Vitrification Experience in the US: Application of Glass Product/Process Control to Other HLW and Hazardous Wastes
Authors: Jantzen Carol M. , Marra James C. 
Published: April 2011

AbstractVitrification is currently the most widely used technology for the treatment of high level radioactive wastes (HLW) throughout the world. At the Savannah River Site (SRS) actual HLW tank waste has successfully been processed to stringent product and process constraints without any rework into a stable borosilicate glass waste since 1996. A unique “feed forward” statistical process control (SPC) has been used rather than statisticalqualitycontrol (SQC). In SPC, the feed composition to the melter is controlledpriorto vitrification. In SQC, the glass product is sampledafterit is vitrified. Individual glass property models form the basis for the “feed forward” SPC. The property models transform constraints on the melt and glass properties into constraints on the feed composition. The property models are mechanistic and depend on glass bonding/structure, thermodynamics, quasicrystalline melt species, and/or electron transfers. The mechanistic models have been validated over composition regions well outside of the regions for which they were developed because they are mechanistic. Mechanistic models allow accurate extension to radioactive and hazardous waste melts well outside the composition boundaries for which they were developed.
Nuclear Waste Immobilization by Vitrification in a Cold Crucible Melter: 3D Magnetic Model of a Melter
Authors: Bonnetier A. 
Published: April 2011

AbstractThe design and development of prototype cold crucible melters for waste vitrification are based on models of the basic physical phenomena, including electromagnetic induction and the thermal and hydraulic properties in natural or forced convection. The complexity of new nuclearized facilities results in significant errors on the results of predictive models based on 2D axisymmetric geometry that can only be resolved by modeling the device in 3D geometry. This document discusses the specification and electromagnetic design of a melter carried out using electromagnetic computation software, FLU3D, developed in 3D geometry by Cedrat. The principles and results of this study are directly applicable to nuclear facilities with allowance for the particular requirements of a nuclearized environment.
In SituCharacterisation of Model UK Nuclear Waste Glasses by X-ray Absorption Spectroscopy Under Process Conditions
Authors: Hyatt Neil C. , Connelly Andrew J. , Stennett Martin C. , Livens Francis R. , Bilsborrow Robert L. 
Published: April 2011

AbstractThe local co-ordination environment of Zr in a model alkali borosilicate glass, of relevance to nuclear waste immobilisation, was studied byin situX-ray absorption spectroscopy between 25 – 1060°C. Analysis of Zr K-edge XANES spectra, in comparison with those of well characterised standards, demonstrated, for the first time, the reversible transformation of ZrO6to ZrO7co-ordination polyhedra at high temperature. This observation was rationalised on the basis of the combined effects of network modifier cation diffusion and thermal expansion.
Glass Formulation Development in Support of Melter Testing to Demonstrate Enhanced High Level Waste Throughput
Authors: Marra James C. , Fox Kevin M. , Peeler David K. , Edwards Thomas B. , Youchak Amanda L. , Gillam James H. , Vienna John D. , Stefanovsky Sergey V. , Aloy Albert S. 
Published: April 2011

AbstractThe U.S. Department of Energy (DOE) is currently processing high-level waste (HLW) through a Joule-heated melter (JHM) at the Savannah River Site (SRS) and plans to vitrify HLW and Low activity waste (LAW) at the Hanford Site. Over the past few years at the Defense Waste Processing Facility (DWPF), work has concentrated on increasing waste throughput. These efforts are continuing with an emphasis on high alumina concentration feeds. High alumina feeds have presented specific challenges for the JHM technology regarding the ability to increase waste loading yet still maintain product quality and adequate throughput. Alternatively, vitrification technology innovations are also being investigated as a means to increase waste throughput. The Cold Crucible Induction Melter (CCIM) technology affords the opportunity for higher vitrification process temperatures as compared to the current reference JHM technology. Higher process temperatures may allow for higher waste loading and higher melt rate.Glass formulation testing to support melter demonstration testing was recently completed. This testing was specifically aimed at high alumina concentration wastes. Glass composition/property models developed for DWPF were utilized as a guide for formulation development. Both CCIM and JHM testing will be conducted so glass formulation testing was targeted at both technologies with a goal to significantly increase waste loading and maintain melt rate without compromising product quality.
Devitrified and Phase Separated Material Found in Simulated High Level Nuclear Waste Glasses Containing Ca and Zn Additions
Authors: Short R. , Turner E. , Dunnett B. , Riley A. 
Published: April 2011

AbstractIn the UK, blended high level nuclear waste (HLW) streams from the Magnox and THORP reprocessing plants are currently vitrified using a lithium sodium borosilicate base glass frit. Laboratory and full size non-radioactive simulations (produced on the Vitrification Test Rig at Sellafield [1]) of these compositions have shown that these glasses need to be melted at circa 1050°C to obtain a reasonable viscosity for pouring. Also, at high waste loadings an alkali molybdate phase (termed “yellow phase”) can form in these glasses [e.g. 2, 3]. Vitrification flowsheets are set to avoid yellow phase formation as this phase is highly corrosive to the inconel melter in the molten state and is partially water soluble at ambient temperature and so may challenge product quality.Ca and Zn additions to the base glass frit have been found to reduce viscosity and allow melt homogeneity and pouring at lower temperatures. It was also theorised that Ca additions could increase the solubility of Mo and thus reduce the likelihood of yellow phase formation. The composition of the phase separated material in as-cast and heat treated specimens of Ca and Zn HLW glasses produced at both laboratory and full scale is examined in this work
Disposability of the UK's Intermediate Level Wastes
Authors: Abraitis Paul K. , Davies Glyn 
Published: April 2011

AbstractThe UK's intermediate level waste (ILW) comprises a range of waste types, which vary widely in terms of physical and chemical properties, radionuclide content (including fissile) and half-life. ILW needs to be conditioned in such a way as to provide confidence that a future disposal facility for such wastes will be able to meet or exceed the basic long-term safety and environmental protection standards. The reactive properties and heterogeneous nature of certain ILW can present waste immobilisation challenges and, depending on the waste conditioning process that is adopted, may ultimately preclude the production of truly passive wasteforms. Of considerable interest is the extent of long-term containment likely to be afforded by the waste container, the wasteform and any engineered barriers within the disposal system. A regulatory view of the current uncertainties is provided and areas where further understanding would be beneficial are identified.
Self-Irradiation of Ceramics and Single Crystals Doped With Pu-238: Summary of 5 Years of Research of the V. G. Khlopin Radium Institute
Authors: Burakov Boris E. , Yagovkina Maria A. , Zamoryanskaya Maria V. , Garbuzov Vladimir M. , Zirlin Vladimir A. , Kitsay Alexander A. 
Published: April 2011

AbstractTo investigate the resistance of actinide host phases to accelerated radiation damage, which simulates radiation induced effects of long term storage, the following samples doped with plutonium-238 (from 2 to 10 wt. %) have been repeatedly studied using XRD and other methods: cubic zirconia, Zr0.79Gd0.14Pu0.07O1.99; monazite, (La,Pu)PO4; ceramic based on Pu-phosphate of monazite structure, PuPO4; ceramic based on zircon, (Zr,Pu)SiO4, and minor phase tetragonal zirconia, (Zr,Pu)O2; single crystal zircon, (Zr,Pu)SiO4; single crystal monazite, (Eu,Pu)PO4; ceramic based on Ti-pyrochlore, (Ca,Gd,Hf,Pu,U)2Ti2O7. No change of phase composition, matrix swelling, or cracking in cubic zirconia were observed after cumulative dose 2.77×1025 alpha decay/m3. The La-monazite remained crystalline at cumulative dose 1.19×1025 alpha decay/m3, although Pu-phosphate of monazite structure became nearly amorphous at relatively low dose 4.2×1024 alpha decay/m3. Zircon has lost crystalline structures under self-irradiation at dose (1.3-1.5)×1025 alpha decay/m3, however, amorphous zircon characterized with high chemical durability. The Ti-pyrochlore after cumulative dose (1.1-1.3)×1025 alpha decay/m3 became amorphous and lost chemical durability. Radiation damage caused crack formation in zircon single crystals but not in the matrix of polycrystalline zircon. Essential swelling and crack formation as a result of radiation damage were observed in ceramics based on Ti-pyrochlore and Pu-phosphate of monazite structure, but not so far in La-monazite doped with 238Pu.
Stability of Cubic Zirconia in a Granitic System Under High Pressure & Temperature
Authors: Gibb Fergus G.F. , Burakov Boris E. , Taylor Kathleen J. , Domracheva Yana 
Published: April 2011

AbstractCubic zirconia is a well known, highly durable material with potential uses as an actinide host phase in ceramic waste forms and inert matrix fuels and in containers for very deep borehole disposal of some highly radioactive wastes. To investigate the behaviour of this material under the conditions of possible use, a cube of ∼ 2.5 mm edge was made from a single crystal of yttriastabilized cubic zirconia doped with 0.3 wt.% CeO2. The cube was enclosed in powdered granite within a gold capsule and a small amount of H2O added before sealing. The sealed capsule was held for 4 months in a cold-seal pressure vessel at a temperature of 780°C and a pressure 150 MPa, simulating both the conditions of a deep borehole disposal involving partial melting of the host rock and the conditions under which the actinide waste form might be encapsulated in granite prior to disposal. At the end of the experiment the quenched, largely glassy, sample was cut into thin slices and studied by optical microscopy, EMPA, SEM and cathodoluminescence methods. The results show that no corrosion of the zirconia crystal or reaction with the granite melt occurred and that no detectable diffusion of elements, including Ce, in or out of the zirconia took place on the timescale of the experiment. Consequently, it appears that cubic zirconia could perform most satisfactorily as both an actinide host waste form for encapsulation in solid granite for very deep disposal and as a container material for deep borehole disposal of highly radioactive wastes (HLW), including spent fuel.
Kinetics of UO2(s) Dissolution in the Presence of Hypochlorite, Chlorite, and Chlorate Solutions
Authors: Sureda Rosa , Casas Ignasi , Giménez Javier , Pablo Joan de 
Published: April 2011

AbstractThe influence of hypochlorite, chlorite and chlorate in the UO2dissolution rate has been studied experimentally using a continuous flow-through reactor. Uranium concentration in each outflow solution was measured as a function of time and dissolution rates were determined once the steady-state was reached. The results obtained show that the influence of the hypochlorite anion concentration on the UO2dissolution rate can be expressed by the following empirical equationrdiss= 10-8.7±0.1•[ClO-]0.28±0.04The dissolution rates obtained in this work were higher than those previously determined in presence of either oxygen or hydrogen peroxide using the same experimental methodology.In contrast, neither chlorate nor chlorite had any significant effect on the UO2dissolution rates under the experimental conditions of this work.
Radionuclide Retardation in Granitic Rocks by Matrix Diffusion and Sorption
Authors: Hölttä P. , Siitari-Kauppi M. , Kelokaski M. , Tukiainen V. 
Published: April 2011

AbstractRadionuclide retardation in mica gneiss, unaltered, moderately and strongly altered tonalite was studied by a thin section, batch, in-diffusion and column methods. Objectives were to examine retention processes in different scales and understand the influence of the rock matrix heterogeneity. Attempts were made for a more detailed interpretation of experiments using migration models used in performance assessments adapted for interpreting the laboratory scale experiments. Batch experiments were explained adequately using matrix diffusion-sorption model, instantaneous kinetic sorption model or model in which both mechanisms were taken into account. A numerical code FTRANS was able to interpret in-diffusion of calcium into the saturated porous matrix. Elution curves of calcium for the moderately and strongly altered tonalite fracture columns were explained adequately using FTRANS code and parameters obtained from in-diffusion calculations. Kd-values for intact rock obtained from fracture column experiments were lower than Kd-values for crushed rock indicating that batch experiments overestimate the retardation of radionuclides. Higher sorption and fair dependence on fraction size was obtained for altered tonalites due to the composition of alteration minerals and large specific surface areas.
Near-Field Modelling in the Safety Assessment SR-Can
Authors: Vahlund C. Fredrik 
Published: April 2011

AbstractSpent nuclear fuel from the Swedish energy programme will be stored in an underground repository situated in saturated fractured rock at a depth of approximately 500 m. This paper describes numerical simulations of radionuclide migration in the near-field (consisting of a canister filled with spent fuel and an engineered system backfilled with swelling clays) for the recently completed safety assessment SR-Can [1] using a Matlab / Simulink code. Handling of input data for the models from the site descriptive programme from on-going investigations at two candidate sites and the numerical modelling concept are discussed.
Characterisation of Radionuclide Migration and Plant Uptake for Performance Assessment
Authors: Mathias Simon A. , Ireson Andrew M. , Butler Adrian P. , Jackson Bethanna M. , Wheater Howard S. 
Published: April 2011

AbstractUnsaturated vegetated soils are an important component in performance assessment models used to quantify risks associated with deep engineered repositories for underground radioactive waste disposal. Therefore, experimental studies, funded by Nirex over nearly 20 years, have been undertaken at Imperial College to study the transfer of radionuclides (Cl-36, I-129, Tc-99) from contaminated groundwater into crops. In parallel to this has been a modelling programme to aid interpretation of the experimental data, obtain parameter values characterising transport in soil and plant uptake and provide new representations of near-surface processes for performance assessment. A particular challenge in achieving these objectives is that the scale of the experimental work (typically ≤ 1m) is much smaller than that required in performance assessment. In this paper, a new methodology is developed for upscaling model results obtained at the experimental scale for use in catchment scale models. The method is based on characterising soil heterogeneity using soil texture. This has the advantage of allowing hydrological and radionuclide transport parameters to be correlated in a consistent manner. An initial investigation into the calculation of effective (i.e. upscaled) hydrological and transport parameters has been undertaken and shows the results to be potentially highly (and non-linearly) sensitive to soil properties. Consequently, they have important implications for future site characterisation programmes supporting a proposed underground waste repository.
Evaluation of Four Imaging Techniques for the Electrical Characterization of Solar Cells
Authors: Berman Gregory M. , Call Nathan J. , Ahrenkiel Richard K. , Johnston Steven W. 
Published: April 2011

AbstractWe evaluate four techniques that image minority carrier lifetime, carrier diffusion length, and shunting in solar cells. The techniques include photoluminescence imaging, carrier density imaging, electroluminescence imaging, and dark lock-in thermography shunt detection. We compare these techniques to current industry standards and show how they can yield similar results with higher resolution and in less time.
Conducting two-phase silicon oxide layers for thin-film silicon solar cells
Authors: Buehlmann Peter , Bailat Julien , Feltrin Andrea , Ballif Christophe 
Published: April 2011

AbstractWe present optical properties and microstructure analyses of hydrogenated silicon suboxide layers containing silicon nanocrystals (nc-SiOx:H). This material is especially adapted for the use as intermediate reflecting layer (IRL) in micromorph silicon tandem cells due to its low refractive index and relatively high transverse conductivity. The nc-SiOx:H is deposited by very high frequency plasma enhanced chemical vapor deposition from a SiH4/CO2/H2/PH3 gas mixture. We show the influence of H2/SiH4 and CO2/SiH4 gas ratios on the layer properties as well as on the micromorph cell when the nc-SiOx:H is used as IRL. The lowest refractive index achieved in a working micromoph cell is 1.71 and the highest initial micromoph efficiency with such an IRL is 13.3 %.
Fabrication and performance of highly textured electrodeposited ZnO back reflector for nc-Si solar cells
Authors: Attygalle Dinesh , Fan Qi Hua , Zhang Shibin , Ingler William B. , Liao Xianbo , Deng Xunming 
Published: April 2011

AbstractTo improve the cell efficiency of thin film solar cells textured back reflectors (BR) are widely used. This is particularly important in a-Si:H based solar cells due to low absorption coefficient at longer wavelengths. In this work we present a cost effective way to fabricate uniformly textured ZnO by using electrochemical methods. Further it was observed that Quantum Efficiency (QE) of shorter wavelengths also improved for highly textured ZnO BR. Together this resulted in more than 2mA increment in short circuit current density (Jsc) and 19% relative improvement in solar cell efficiency over sputter deposited BR. A possible mechanism responsible for the improved blue QE is also discussed.
Studies on Backside Al-Contact Formation in Si Solar Cells: Fundamental Mechanisms
Authors: Sopori Bhushan , Mehta Vishal , Rupnowski Przemyslaw , Moutinho Helio , Shaikh Aziz , Khadilkar Chandra , Bennett Murray , Carlson Dave 
Published: April 2011

AbstractWe have studied mechanisms of back-contact formation in screen-printed Si solar cells by a fire-through process. An optimum firing temperature profile leads to the formation of a P-Si/P+- Si/ Si-Al eutectic/agglomerated Al at the back contact of a Si solar cell. Variations in the interface properties were found to arise from Al-Si melt instabilities. Experiments were performed to study melt formation. We show that this process is strongly controlled by diffusion of Si into Al. During the ramp-up, a melt is initiated at the Si-Al interface, which subsequently expands into Al and Si. During the ramp-down, the melt freezes, which causes the doped region to grow epitaxially on Si, followed by solidification of the Si-Al eutectic. Any agglomerated (or sintered) Al particles are dispersed with Si. Implications on the performance of the cell are described.
Wireless transmission monitoring in a geological disposal repository (II) Research and Development
Authors: Takamura Hisashi , Shimbo Hiroshi , Okutsu Kazuo , Suyama Yasuhiro , Aoki Kazuhiro , Wada Ryutaro 
Published: April 2011

AbstractThe development of the wireless transmission monitoring in the geological disposal repository, the underground laboratories, the test facilities and the demonstration area, will present an opportunity to provide greater flexibility and robustness to the confirmation of the barrier performance and therefore safety of repository [1]. So as to realize the wireless transmission monitoring especially in the betonite barrier, RWMC has been researching and developing the wireless data transmission system which uses the very low frequency (VLF: around 1 kHz) electromagnetic wave. In this system, transmitting and receiving is conducted through loop coil antennas. The overall transmission system is digitized and maximum 19 sensors can be connected to one transmitter. Transmission distance can be selected from several meters to several hundred meters.This paper firstly presents the behavior of VLF electromagnetic wave propagation in the rock mass and the underground facility revealed by the in-situ transmission experiment and the analytical method evaluating the behavior of the VLF electromagnetic field in various environments. Development results of the transmitting antenna and the improvement of the transmission performance are secondly shown. The technical feasibility and the future R&D plan of the wireless monitoring in the repository are also explained.
Disruptive Effects on a HLW Repository ue to Uplift-Erosion in the Distant Future
Authors: Miyahara Kaname , Inagaki Manabu , Kawamura Makoto , Ebina Takanori , McKinley Ian G. 
Published: April 2011

AbstractIn Japan, uplift/erosion scenarios must be analysed even if they occur far in the future, as no assessment cut-off times have yet been defined. For this purpose, an argumentation method is developed to allow sensible scenarios to be constructed. The consequences of erosion of the repository may be better estimated in terms of radionuclide fluxes and these compared with those of naturally occurring radionuclides. This paper discusses procedures to derive relevant conceptual models and resultant analyses in a credible manner, which illustrates the effectiveness and robustness of the HLW disposal system.
Influences of subsurface geological structure neighboring geological repository on earthquake motion of the site
Authors: Oouchi Taishi , Tsuchi Hiroyuki , Ota Tetsuya , Hane Koji , Sasaki Toru 
Published: April 2011

AbstractAccording to recent seismic observation records, there are some cases where unexpectedly large seismic motion was observed deep underground and that was larger than at the surface. The factors influencing such phenomena are assumed to be deep geological structures with topographic irregularity, velocity structure and non-linearity of subsurface layers. These factors should be taken into account in the earthquake-resistant design of a geological repository. The influence of a deep underground geological structure with topographic irregularity on ground motion has been studied and it has been confirmed that such a structure have a significant impact on ground motion and the constructive interference of waves may result in strong earthquake ground motion in the vicinity of a structural boundary deep underground.