bluuebunny/crossref_metadata_2025 huggingface dataset:
Grimsel Test Site - Phase VI: Review of Accomplishments and Next Generation of In-Situ Experiments Under Repository Relevant Boundary Conditions
Authors: Blechschmidt Ingo , Vomvoris Stratis , Rueedi Joerg , Martin Andrew James
Published: April 2011

The Grimsel Test Site owned and operated by Nagra is located in the Swiss Alps (www.grimsel.com). The Sixth Phase of investigations was started in 2003 with a ten-year planning horizon. With the investigations and projects of Phase VI the focus has shifted more towards projects assessing perturbation effects of repository implementation and projects evaluating and demonstrating engineering and operational aspects of the repository system. More than 17 international partners participate in the various projects, which form the basic organisational “elements” of Phase VI. Scientific and engineering interaction among the different projects is ensured via an annual meeting and several experimental team meetings throughout the year. On-going projects include: evaluation of full-scale engineered systems under simulated heat production and long-term natural saturation (NF-Pro/FEBEX), gas migration through engineered barrier systems (GMT, finished this year), emplacement of a shotcrete low-pH plug (ESDRED/Module IV), testing and evaluation of standard monitoring techniques (TEM).

Numerous in-situ experiments with inactive tracers and radionuclides were successfully carried out over the past few years at the Grimsel Test Site (GTS). For the GTS Phase VI, three major projects have been initiated to simulate the long-term behaviour of contamination plumes in the repository near-field and the surrounding host rock:

•The CFM (Colloid Formation and Migration) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides

•The LCS (Long-Term Cement Studies) project, which aims at improving the understanding of low-pH cement interaction effects in water conducting features

•The LTD (Long-Term Diffusion) project, which aims at in-situ verification of long-term diffusion concepts for radionuclides

As Phase VI approaches its mid-term point, what are the next steps planned? The accomplishments assessed to date and the opportunities with the on-going projects as well as new projects – currently under discussion – are presented herein
Magnetite Sorption Capacity for Strontium as a Function of pH
Authors: Pablo Joan de , Rovira Miquel , Giménez Javier , Casas Ignasi , Clarens Frederic
Published: April 2011

The ubiquity of iron oxide minerals and their ability to retain metals on their surface can represent an important retardation factor to the mobility of radionuclides. In a deep repository for the spent nuclear fuel, the intrusion of the groundwater might produce the anoxic corrosion of the iron, with magnetite as one of the end-products. In this study, as expected considering the strontium speciation in solution, strontium is sorbed onto magnetite at alkaline pH values while at acidic pH the sorption is negligible. Magnetite is able to sorb more than the 50% of the strontium from a 8·10-6 mol·dm-3 solution at the pH range representative of most groundwater (7-9). A surface complexation model has been applied to the experimental data, allowing to explain the results using the Diffuse Layer Model (DLM) and considering the formation of the inner-sphere complex >FeOHSr2+ (with a calculated logK=2.7±0.3). Considering these data, the magnetite capacity to retain strontium and other radionuclides is discussed
Long-Term Predictions of the Concentration of a-isosaccharinic Acid in Cement Pore Water
Authors: Glaus Martin A. , Loon Luc R. Van , Schwyn Bernhard , Vines Sarah , Williams Steve J. , Larsson Peter , Puigdomenech Ignasi
Published: April 2011

The long-term prediction of the equilibrium concentration of α-isosaccharinic acid (α-ISA) in cement pore water is a crucial step in the assessment of the role of cellulose in the safety of a cementitious repository. The aim of the present contribution is to summarise recent efforts in identifying the most important processes leading to the formation or degradation of α-ISA and in predicting its most likely concentrations in cement pore water. The issues considered are the kinetics involved in the formation of α-ISA, reactions of α-ISA with dissolved or solid compounds that may lead to limitations of its pore water concentrations and the chemical stability of α-ISA in a heterogeneous alkaline environment. Some new results are presented showing that α-ISA is degraded to low-molecular weight organic compounds in the presence of oxygen, whereas such processes occur only to a minor extent under anaerobic conditions. It is concluded that the processes involved in the degradation of cellulose under alkaline conditions are not sufficiently understood to explain fully the observed concentrations of α-ISA in long-term experiments.
Release Behaviour of Sr-90 From Hydraulically Retrieved ILW Sludge
Authors: Hastings J J
Published: April 2011

Globally, the nuclear industry has a large number of legacy wastes that are stored in ponds, silos and tanks that are nearing the end of their design lifetime and hence said wastes need processing. In the UK there are significant quantities of radioactive sludge that have arisen from the corrosion of early Magnox fuel cans which have been stored underwater. As part of the present aggressive clean-up programme these materials will be retrieved, separated, processed and immobilised as dry waste forms for long-term storage. It is envisaged that hydraulic retrieval will be used for these ILW sludges resulting in some activity being released from the sludge phase to the process liquors challenging downstream ion exchange effluent treatment plants.

In order to understand this challenge, experiments have been conducted on sludge in ILW storage ponds and during sludge transfer operations to study the activity released from said sludges. In particular the solubility, adsorption behaviour of Sr-90 is discussed and how this and other aspects of the sludge chemistry impact upon the ion exchange effluent treatment process. The novel methodologies employed to obtain this data is also discussed.
Modelling Transport of 14 C-Labelled Natural Organic Matter (NOM) in Boom Clay
Authors: Ionescu Alice , Maes Norbert , Mallants Dirk
Published: April 2011

In Belgium, the Boom Clay formation is considered to be the reference formation for HLW disposal R&D. Assessments to date have shown that the host clay layer is a very efficient barrier for the containment of the disposed radionuclides. Due to absence of significant water movement), diffusion - the dominant transport mechanism, combined with generally high retardation of radionuclides, leads to extremely slow radionuclide migration. However, trivalent lanthanides and actinides form easily complexes with the fulvic and humic acids which occur in Boom Clay and in its interstitial water. Colloidal transport may possibly result in enhanced radionuclide mobility, therefore the mechanisms of colloidal transport must be better understood. Numerical modeling of colloidal facilitated radionuclide transport is regarded an important means for evaluating its importance for long-term safety.

The paper presents results from modeling experimental data obtained in the framework of the EC TRANCOM-II project, and addresses the migration behavior of relevant radionuclides in a reducing clay environment, with special emphasis on the role of the Natural Organic Matter (NOM) [1]. Percolation type experiments, using stable 14C-labelled NOM, have been interpreted by means of the numerical code HYDRUS-1D [2]. Tracer solution collected at regular intervals was used for inverse modeling with the HYDRUS-1D numerical code to identify the most likely migration processes and the associated parameters. Typical colloid transport submodels tested included kinetically controlled attachment/detachment and kinetically controlled straining and liberation.
Comparative Analysis of Results From Deterministic Calculations of the Release of Radioactivity From Geological Disposal of Spent Fuel in Crystalline Rocks
Authors: Prvakova Slavka , Amosov Pavel V. , Nilsson Karl-Fredrik
Published: April 2011

This paper presents results from deterministic calculations of radionuclide migration in a deep geological environment. The concept assumes single canister with spent nuclear fuel situated in bentonite (near-field) and surrounded by crystalline host rock (far-field). The results are presented in the form of release rates from the near-field and far-field, which contains also a part of advective release from the system of two single fractures. Additionally, radiological risk is evaluated in the form of dose rates for a water drinking scenario for an exposed population group. The analyses have been done by using the methodologies and computer codes used at the Institute for Energy EC-JRC in the Netherlands and the Mining Institute KSC RAS in Russia.
Evaluating Chemical Toxicity of Surface Disposal of LILW-SL in Belgium
Authors: Mallants D. , Wang L. , Weetjens E. , Cool W.
Published: April 2011

ONDRAF/NIRAS is developing and evaluating a surface disposal concept for low and intermediate level short-lived radioactive waste (LILW-SL) at Dessel, Belgium. In support of ONDRAF/NIRAS's assignment, SCK•CEN carried out long-term performance assessment calculations for the inorganic non-radioactive components that are present in LILW-SL. This paper summarizes the results obtained from calculations that were done for a heavily engineered surface disposal facility at the nuclear zone of Mol/Dessel. The calculations address the migration of chemotoxic elements from the disposed waste to groundwater.

Screening calculations were performed first to decide which non-radioactive components could potentially increase concentrations in groundwater to levels above the groundwater standards. On the basis of very conservative calculations, only 6 out of 41 chemical elements could not be classified as having a negligible impact on man and environment. For each of these six elements (B, Be, Cd, Pb, Sb, and Zn), the source term was characterized in terms of its chemical form (i.e., metal, oxide, or salt), and a macroscopic transport model built that would capture the small-scale dissolution processes relevant to element release from a cementitious waste container. Furthermore, reliable transport parameters in support of the convection-dispersion-retardation (CDR) transport calculations were determined. This included derivation of (1) solubility for a cementitious near field environment based on thermodynamic equilibrium calculations with The Geochemist's Workbench, and (2) distribution coefficients based on a compilation of literature values. Scoping calculations illustrated the effects of transport parameter uncertainty on the rates at which inorganic components in LILW-SL leach to groundwater.
Characterisation of Partial Melting and Solidification of Granite E93/7 by the Acoustic Emission Technique
Authors: Spasova Lyubka M. , Gibb Fergus G.F. , Ojovan Michael I.
Published: April 2011

The acoustic emission (AE) technique was used to detect and characterise the processes associated with generation of stress waves during melting and solidification of granite E93/7 at a pressure of 0.15 GPa. The AE signals recorded as a result of partial melting of the granite at a temperature of 780°C and subsequent solidification during cooling were distinguished from the equipment noise and their parameters used to characterise the AE sources associated with the phase transformations during melting and solidification of the granite. The mechanisms generating AE during granite melting were differentiated by AE signals with their highest peaks in the frequency spectrum at 170 and 268 kHz. The transformation of the liquid into glass during solidification of the partially melted granite generated AE waves in an essentially broad range of frequencies between 100 and 300 kHz. This preliminary work demonstrates the potential of the AE technique for use in applications related to deep borehole disposal of radioactive wastes.
SIMS Study of C, O and N Impurity Contamination for Multi-Crystalline Si Solar Cells
Authors: Wang Larry , Hockett R. S.
Published: April 2011

This paper is a case study of using SIMS to quantitatively measure C, O and N impurity contamination at two sequential commercial process steps: (1) Si feedstock: 7N (modified Siemens) and 5N feedstock (UMG-Si); and (2) multi-crystalline (mc-Si) solar wafers: cut and etched, from directional solidification bricks grown from 7N and 7N/5N (80:20) feedstock. The conclusion of this study is twofold: (a) the primary opportunity to reduce C, O and N contamination in mc-Si solar cells is at the directional solidification process, and (b) the costly specification of highly pure Si feedstock is unnecessary from a C, O and N perspective if a directional solidification process is used.
Effects of Deposition Parameters on the Structure and Photovoltaic Performance of Si Thin Films by Metal Induced Growth
Authors: Mersich Peter T. , Verma Shubhranshu , Anderson Wayne A. , Giese Rossman F.
Published: April 2011

A metal-induced growth (MIG) process was employed to deposit thin films of microcrystalline silicon (μc-Si) for solar cell applications. Due to different grain orientations of the crystals, the absorption coefficient of μc-Si is about 10 times higher than the absorption coefficient of single crystalline Si. The properties of the Si film were investigated resulting from variations in several parameters. A range of Ni and Co thicknesses were examined from 7.5 nm to 60 nm including combinations of the two, while the dc sputtering power was stepped up from 150 W to 225 W. The structure of the resulting film was studied using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD). SEM of the film revealed that 5 hr of Si deposition at 150 W yields a film thickness of 6.5 μm and a maximum grain size of about 0.6 μm. EDS data showed that at the middle of the Si film the atomic percentage of the Si was 99.17%. XRD data showed that the dominant crystal orientation is {220}. To characterize the photovoltaic properties of the μc-Si, Schottky photodiodes were fabricated. Ni alone as the seed layer resulted in ohmic behavior. With Co only, MIG formed a rectifying contact with open-circuit voltage (V∝). The combination of Co layered over Ni formed better thin films and gave a Voc of 0.24 V and short-circuit current density (Jsc) of 5.0 mA/cm2 since the Co prevents Ni contamination of the top of the grown Si layer.
CdTe Films on Mo/Glass Substrates: Preparation and Properties
Authors: Valdna Vello , Grossberg Maarja , Hiie Jaan , Kallavus Urve , Mikli Valdek , Traksmaa Rainer , Viljus Mart
Published: April 2011

Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radiation detectors, and solar cells where p-type CdTe is needed. p-type conductivity of CdTe is mainly caused by the chlorine-based A-centers, and in part, by the less stable copperoxygen complexes. As a rule, CdTe films are recrystallized by the help of a cadmium chloride flux that saturates CdTe with chlorine. In chlorine-saturated CdTe A-centers are converted to isoelectronic complexes that cause resistivity increasement of CdTe up to 9 orders of magnitude. Excess copper and oxygen or group I elements as sodium also deteriorate the p-type conductivity of CdTe like excess chlorine. p-type conductivity of CdTe can be restored e.g. by the vacuum annealing which removes excess chlorine from the film. Unfortunately, treatment that betters ptype conductivity of the CdTe film degrades the junction of the superstrate configuration cells. In this work we investigate possibilities to prepare p-type CdTe films on the molybdenum coated glass substrates. Samples were prepared by the vacuum evaporation and dynamic recrystallization of 6N purity CdTe on the top of Mo-coated glass substrates. Then samples were recrystallized with cadmium chloride flux under tellurium vapour pressure. Results of the test studies on the structure and electronic parameters of samples are presented and discussed.
The Development of Sprayed Backfill Technology
Authors: Jaroslav Pacovsky , Jiří Svoboda , Jiří Št'ástka
Published: April 2011

The Centre of Experimental Geotechnics, CTU in Prague has recently launched a sprayed backfill technology development programme. Such technology will, most probably, be used during the future construction of deep underground radioactive waste repositories.

The safe disposal of radioactive waste in deep underground geological repositories assumes the construction of a multi-barrier system the aim of which will be to eliminate the potential penetration of hazardous radionuclides into the biosphere over a time span of several hundred thousand years.

With regard to the location in the repository in which the containers will be placed, bentonite will seal the space between the container and the rock mass in the form of a highly compacted bentonite block, while access galleries to the nests will be backfilled with a mixture of natural bentonite and rock. This mixture will be compacted in layers using compacting machinery thus ensuring maximum backfill density during compaction. Following compaction, however, spaces will remain in the gallery vault to which such compacting machines will be unable to gain access. Sprayed clay (sprayed backfill) technology, however, will allow the filling of such voids by injecting backfill so that the material compaction level obtained using this method is at least the same as the backfill compaction level resulting from that using standard compacting machinery (vibration roller, vibration plate compactor etc.).

Sprayed backfill technology is based on shotcrete technology which is a method commonly applied today in the construction of underground structures. Sprayed backfill technology development may involve the use of concrete spraying machines; however the parameter requirements for the spraying of bentonite backfill differ in principal from those which apply to shotcrete.

The article will provide information on the development of sprayed backfill technology, the machinery employed and the sprayed material as well as research results obtained to date.
Studies on radionuclide transport behaviour–The next generation of in-situ experiments at the Grimsel Test Site
Authors: Martin Andrew James , Blechschmidt Ingo
Published: April 2011

Two recent ongoing major projects at the Grimsel Test Site (GTS) (www.grimsel.com) that were initiated to simulate the long-term behaviour of radionuclides in the repository near-field and the surrounding host rock are presented: the Colloid Formation and Migration (CFM) project, which focuses on colloid generation and migration from a bentonite source doped with radionuclides and the Long-Term Diffusion (LTD) project, which aims at in-situ verification and understanding of the processes that control the long-term diffusion of repository-relevant radionuclides. So far, the CFM project has principally involved: development and implementation of a state-of-the-art sealing concept to control hydraulic gradients in a shear zone to imitate repository-relevant conditions; extensive laboratory studies to examine bentonite erosion and colloid formation in a shear zone; and, development of models to estimate colloid formation and migration. The next stage will be to assess the behavior of bentonite colloids generated from a radionuclide spiked bentonite source-term emplaced into the controlled flow field of the shear zone. This will be coupled with further extensive laboratory studies in order to refine and evaluate the colloid models currently used in performance assessments. The LTD project consists of: a monopole diffusion experiment where weakly sorbing and non-sorbing radionuclides (3H, 22Na, 131I, 134Cs) have been circulating and diffusing into undisturbed rock matrix since June 2007; experiments to characterise pore space geometry, including determination of in-situ porosity with 14C doped MMA resin for comparison with laboratory derived data; a study of natural tracers to elucidate evidence of long-term diffusion processes; and, an investigation of the in-situ matrix diffusion paths in core material from earlier GTS experiments. Future experiments will focus on diffusion processes starting from a water-conducting feature under realistic boundary conditions.
Measurement of HLW glass dissolution/alteration kinetics by using micro-reactor flow-through test method
Authors: Inagaki Y. , Mitsui S. , Makigaki H. , Idemitsu K. , Arima T. , Banba T. , Noshit K.
Published: April 2011

A new type of flow-through test method using micro-reactor was developed and applied to measurement of the dissolution/alteration kinetics for a Japanese type of simulated HLW glass, P0798. In this test method, a face of coupon shaped glass specimen (30mm × 10mm × 4mm size) is in contact with a micro-channel (20mm length, 2mm width, 0.16mm depth) constructed on a PTFE (Teflon®) plate, and a solution is injected into the inlet of micro-channel at a constant rate. The injected solution, which flows through the micro-channel reacting with the glass to the outlet, is retrieved at certain intervals to be analyzed for determination of the glass dissolution/alteration rate. After the test, the glass specimen removed from the micro-reactor is subjected to surface analyses. This test method has major features as follows, 1) any controlled solution condition can be provided over the test duration, 2) a relatively high S/V ratio can be provided by use of micro-reactor in spite of using coupon shaped glass specimen, which results in precise and consistent analyses of both the solution and the reacted glass surface, 3) the test apparatus is simple with compact size and easy operation, which allows a flexible setup of test conditions. By use of this test method the dissolution/alteration rate for P0798 glass was measured as a function of pH, temperature, and time, and the results indicated that this test method is applicable and suitable for evaluation of the dissolution/alteration kinetics.
Use of Archaeological Glass to Predict the Long-Term Behavior of HLW
Authors: Gin S. , Verney-Carron A. , Libourel G.
Published: April 2011

The predictability of models describing long-term nuclear glass behavior in a geological repository can be tested by means of natural or archaeological analogs. This study covers fractured archaeological glass blocks from a shipwreck discovered near the Mediterranean island of Embiez (France). The blocks were examined mainly because of their morphological analogy with nuclear glasses. Fractured after production (as in the case of nuclear glass), these blocks had been leached for 1800 years in seawater. The laboratory investigation led to the development and subsequent validation on archaeological objects of a geochemical model capable of accurately simulating the coupling between chemistry and transport to account for the alteration state of the cracks according to their geometric characteristics. Laboratory experiments allowed us to determine the kinetic and thermodynamic parameters for modeling glass alteration. The model was then tested against short-term experiments before simulating the crack alteration over 1800 years. We show that cracks in the outer regions of the block are the most severely altered because of rapid solution renewal, whereas internal cracks are very slightly altered because of a rate-limiting effect of water transport due to the formation of secondary phases. This study also establishes a direct link between data obtained at lab scale and the long-term evolution of a complex system in a natural environment, indicating that the key phenomena have been identified experimentally. The analogous behavior of archaeological and nuclear glass during leaching experiments and the similarities in their crack networks allow us to consider applying the model to nuclear glasses under geological repository conditions. This study clearly shows that the internal crack network does not play a major role in the overall long-term alteration of archeological glass blocks. The issue of the transposition studies will be to determine whether this conclusion can be generalized to nuclear glasses.
Composition Changes and Future Challenges for the Sellafield Waste Vitrification Plant
Authors: Riley A. , Walker S. , Gribble Nick R.
Published: April 2011

The Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquors produced during reprocessing of spent nuclear fuel by bonding the fission products as metal oxides into a borosilicate glass matrix. This provides a stable and durable waste form suitable for safe long term storage and ultimate disposal.

WVP was commissioned with feed from reprocessing of Magnox reactor fuel. This material is relatively low in fission product content per tonne of fuel, but contains significant Al and Mg from fuel cladding. WVP also routinely treats a blended feed made from a mixture of Magnox and Oxide reprocessing products. The Oxide fuel from Light Water Reactor (LWR) and Advanced Gas Cooled (AGR) power stations is of higher burnup and contains more fission products per tonne of fuel, also Gd and other process additives. Blending allows 25% incorporation of waste oxides by weight in glass to be achieved routinely.

Recent programmes of development work in WVP have been aimed at increasing incorporation rates for these feeds, to reduce the number of waste containers produced for disposal. Work has also focussed on increasing the throughput of WVP, to more rapidly treat current stocks of liquid reprocessing waste, both by increasing the feed rate and by improving the lifetime of key components to improve plant availability.

Future challenges for WVP include flowsheet changes to treat historic stocks of reprocessing wastes containing high U, Fe and Cr. Washout of solids from the base of waste storage tanks in preparation for decommissioning is also likely to give high Mo feeds. Development of flowsheet and glass formulation to accept these changes in feed composition will be a key objective of future work.
The Impact of Increased Waste Loading on Vitrified HLW Quality and Durability
Authors: Gribble Nick R , Short Rick , Turner Edward , Riley Andrew D
Published: April 2011

The Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquid waste (HAL) arising from the reprocessing of spent nuclear fuel in the UK. In order to optimise WVP operations a full scale working replica of a WVP processing line, the Vitrification Test Rig (VTR), was constructed to processes non-active HAL simulants. Recently the VTR has been used to determine an operational envelope for the vitrification of HAL from Magnox reprocessing at a waste oxide incorporation rate in glass of up to 35wt% (compared to a “standard” incorporation rate of 25wt%). This paper discusses the differences in operating conditions necessary to achieve acceptable waste throughput at the increased incorporation rate. The chemical durability of the resulting vitrified product is also discussed, along with the formation of secondary phases, and a comparison is drawn between 35wt% incorporation glasses and products made at the standard 25wt% incorporation.
Measurement of initial dissolution rate of P0798 simulated HLW glass by using micro-reactor flow-through test method
Authors: Makigaki H. , Inagaki Y. , Idemitsu K. , Arima T. , Mitsui S. , Banba T. , Noshita K.
Published: April 2011

We applied a new type of flow-through test method using micro-reactor consisting of a simple test apparatus with compact size to measurement of the dissolution rate of a Japanese type of simulated waste glass (P0798 glass). In this test method, a solution flows through a micro-channel (20 mm length, 2 mm width, 0.16 mm depth) in contact with a face of coupon shaped glass specimen, and the output solution is retrieved at certain intervals to be analyzed for determination of the glass dissolution rate. By using this test method the initial dissolution rate of glass matrix or forward dissolution rate was measured as a function of pH (3 to 11) and temperature (25°C to 90°C). The present test results indicated that the initial dissolution rate has ‘V-shaped’ pH dependence, and the effect of pH on the dissolution rate decreases with increase in temperature similar to the results measured by using the Single-pass flow-through (SPFT) method. The present test results also indicated that the dissolution of B is controlled by diffusion process and that of Si is controlled by surface reaction process.
Microwave Vitrification of Model Heavy Metals Carriers From Wastewaters Treatment
Authors: Kovacova Milota , Lovas Michal , Jakabsky Stefan , Romero Maximina , Rincon Jesus Ma
Published: April 2011

The metallurgical industry of ferrous and non-ferrous metals produce huge amount of wastes. In Slovakia, the factory for nickel production was closed in 1993, but around 5.5 kt of wastes remain in a dump. This waste was used as a model sorbent of heavy metals (Cu, Cd, Co) from wastewater treatments. The TCLP (Toxicity Characteristic Leaching Procedure) test of precipitated heavy metals on waste materials has confirmed the necessity of waste stabilization. The microwave vitrification was applied because of a high content of iron in waste. After vitrification, the chemical durability and microhardness by indentation have been tested in the glassy and glassceramics obtained.
Development of scenario analysis and database for quantitative analysis of microbial effects on the repository performance
Authors: Yoshikawa Hideki , Inagaki Manabu , Miyasaka Iku
Published: April 2011

A scenario analysis was performed for microbial effect on the performance assessment (PA) of the high-level radioactive waste disposal system. Based on review of recent literature on PA and some results of our experiment, possible scenario of microbial effects on the Japanese high-level radioactive waste disposal system were analyzed. The result of the analysis shows that the microbial effect on groundwater evolution, which is caused by the microbial redox reaction, is one of the most important issues in assessing PA. The evolution not only affects radionuclide migration but also the life-time of metal overpack corrosion.

To assess the microbial effect on groundwater evolution, a numerical estimation code is required, with reliable parameters for analysis of microbial activities used in the code. A biological parameter database has been developed to give the growth and metabolism of the six typical microbial groups to be used in the estimation code. For this purpose, about 573 data from 95 papers were examined to obtain effective data for disposal. The database is composed of significant data like specific growth rate, maximum growth rate, constant decay rate, and experimental condition for model assessment.
Effect of Calcium Silicate Hydrate Precipitates at Cementitious and Bentonite Material Interface on Long-Term Engineered Barrier System Performance in TRU Waste Disposal Facilities
Authors: Kurosawa Susumu , Sakamoto Hiroyuki , Nitta Kiyofumi , Numako Chiya , Haga Kazuko , Shibata Masahito , Sato Tsutomu , Nakazawa Toshiyuki , Owada Hitoshi
Published: April 2011

Chemical conditions and mass transport properties of engineered barrier systems in TRU waste facilities would change with time due to the interaction of cement/bentonite materials. (‘TRU waste’ is one of categories of the radioactive wastes and contains a significant amount of alpha-emitting transuranic nuclides. In some countries, these wastes are classified into the Intermediate Level Waste (ILW).) Previous numerical model analyses to assess the long-term performance of engineered barrier systems in TRU waste repositories predicted to form Calcium Silicate Hydrate (C-S-H) species at the interface between the cementitious and bentonite materials. If C-S-H precipitates in the bentonite side of the boundary, mass transport in the bentonite buffer decreases and mineralogical alterations are expected to be restricted for a long period. The evidence of C-S-H precipitation in the bentonite side, however, still has not been identified in the former experimental studies. To improve the reliability of numerical analyses, immersion experiments were performed using contact samples of cementitious and bentonite materials, and X-ray absorption fine structure (XAFS) analysis was carried out to detect C-S-H precipitation at the contacting interface. Precipitation of C-S-H was confirmed from the obtained XAFS spectra. This result is one of the evidences to show the validity of the current numerical model analyses, which suggests that the bentonite buffer performance as an engineered barrier would be kept over a long period.
Leaching of Bituminized Waste Products (BWP) by Pure Water: The Contribution of NMR Techniques for the Investigation of the Porous Layer
Authors: Le Feunteun S. , Diat O. , Guillermo A. , Ledieu A. , Poulesquen A.
Published: April 2011

The aim of this study is to improve the understanding of the water infiltration within Bituminized Waste Products (BWP) and the associated phenomena such as the development of the porous layer, the matrix swelling or the water uptake kinetics. Two sets of leaching experiments have been performed on synthesized model samples that are constituted by inactive soluble and/or insoluble salts (40% wt) embedded in bitumen. Large samples were used to quantify the water uptake kinetics and to control the macroscopic swelling of the matrixes during experiments. Smaller samples were used to characterize the depth distribution of the infiltrated water and its motion properties by NMR techniques (1H-T1 relaxation times and 1D-NMR imaging). These techniques enabled us to study the influence of the matrix chemical composition on the water advance in depth as a function of the leaching time. Results show that insoluble salts have a significant influence on water transport while soluble salts entail the development of large porosities. Preliminary results obtained with an original method based on the measurement of NMR relaxation times along the water concentration in depth are presented. They illustrate the great potential of the approach to further improve our knowledge on the establishment of the aqueous network.
Study of the Processes Related to the Water Uptake of Eurobitum Bituminized Radioactive Waste: Effect of Salt Concentration
Authors: Mariën An , Smets Steven , Valcke Elie
Published: April 2011

A coupled hydro-chemical-mechanical constitutive law for the Belgian Eurobitum bituminized waste is being developed by the International Centre for Numerical Methods and Engineering (Polytechnical University of Cataluña, Spain) to contribute to the study of the compatibility of Eurobitum with Boom Clay as a geological disposal environment. A large experimental programme is ongoing at SCK•CEN to support the development of a constitutive law for Eurobitum. Water uptake tests are being performed under different conditions to obtain insights in the parameters that influence the water uptake behaviour of Eurobitum. Furthermore, Environmental Scanning Electron Microscopy and microfocus X-ray Computer Tomography are used to characterize hydrated samples in order to improve the understanding of the water uptake processes.

The salt content, the distribution of the salt crystals, and the membrane efficiency in the Eurobitum samples affect the swelling and pressure increase rate. High membrane efficiencies and a large amount of hygroscopic salts inside the Eurobitum samples result in very high pressures when almost no swelling is allowed. The pressure in small inactive samples with 28 wt.% NaNO3has risen to ∼19 MPa after ∼3 years of hydration in nearly constant volume conditions. Slower pressure increase rates are being measured for samples with 6, 12, 18, and 33 wt.% NaNO3.
Colloid and Radionuclide Transport in Granite Under Low Water Flow Rates Expected in a Geological Repository
Authors: Albarran Nairoby , Missana Tiziana , Alonso Ursula , Garcia-Gutierrez Miguel , Mingarro Manuel , Lopez Trinidad
Published: April 2011

Colloids generated from the engineered barriers of a high level radioactive waste repository (HLWR) emplaced in crystalline rock could play a significant role in radionuclide transport and they are of concern for the safety assessment of these repositories.

The main objectives of this study are: a) to analyze the transport properties of colloids in a crystalline fractured rock under hydrodynamic conditions as similar as possible to those expected in a repository (i.e. low flow rates) and b) to discuss the effects of their presence on the transport of radionuclides.

Transport experiments with bentonite and latex colloids in a fractured granite column from the Grimsel Test Site (Switzerland) were carried out, under geochemical conditions ensuring colloid stability (alkaline and low ionic strength water). Transport experiments were also carried out with 85Sr and 233U and the results with and without the presence of bentonite colloids were compared.

Colloid filtration in the fracture was always observed, even when colloids presented high stability and the conditions were unfavorable to colloid attachment to rock surfaces, being both the colloids and the rock negatively charged and the fracture surface smooth. The retention in the fracture depended on the water flow rate, increasing the retention as the water flow decreased.

This work illustrates as both the mobile and retained fraction of colloids, which strongly depend on the hydrodynamic conditions, are of importance in the overall radionuclide mobility.
Competitive Sorption of Metal Ions From Aqueous Solution Onto Sand
Authors: Morandi Sonia , Giacobbo Francesca , Mariani Mario , Ros Mirko Da
Published: April 2011

The major part of groundwater contaminants strongly interact with soils and aquifer rocks. Therefore sorption processes on porous matrix are of utmost importance in the frame of the nuclear waste disposal. The objectives of this study were to evaluate sorption uptake by silica sand of some safety-relevant metal ions such as Cs+, Sr2+, Cu2+, Ni2+ and to investigate the existence of competitive sorption processes between these ions. To this aim, kinetic and equilibrium, mono-component and multi-component, batch experiments were carried out in order to study: i) the influence of metal concentration, pH and contact time, on sorption onto silica sand of the above ions in aqueous solution, and ii) the presence of competition phenomena. Sorption data were well fitted by Langmuir and Freundlich models. Multi-component tests show that the uptake of each ion is reduced in presence of other ions in solution with respect to mono-component batch tests results and that competition between species appears influenced by the equilibrium times of the single species in solution and by pH.
Extending the SFR Repository in Order to Handle Decommissioning Waste From the Swedish NPPs
Authors: Vahlund Fredrik , Gordon Anna
Published: April 2011

Low- and intermediate-level operational waste from the Swedish nuclear power plants is stored in the SFR repository. The facility is located in the bedrock at a depth of approximately 50 m and has been in operation for 20 years. According to present plans, all Swedish nuclear power plants will have been decommissioned by the end of the 2040s. The decommissioning phase will start by initially decommission the two Barseback reactors that have been non-operational since 1999 and 2005. In order to host the decommissioning waste, the storage volume of the SFR repository must be extended with approximately 140,000 m3. To do this, a project is ongoing with the objective of submitting an application to extend SFR by 2013 and the superior aim of having the facility in operation year 2020.
The Behaviours of Cementitious Materials in Long Term Storage and Disposal: An Overview of Results of the IAEA Coordinated Research Project
Authors: Drace Zoran , Ojovan Michael I.
Published: April 2011

Cementitious materials are widely used in waste management systems with different aims and requirements for long term performance. Both conventional and novel cementitious materials are used to create reliable immobilising elements for safe storage and disposal of wastes. The barrier elements as well as interactions envisaged between various components are important to ultimately ensure the overall safety of a storage/disposal system. The behaviour and performance of cementitious materials including waste package components, wasteform and backfilling were analysed within the IAEA Coordinated Research Project which involved 26 research organizations from 21 Member States MS). The paper presents briefly the main research outcomes for conventional cementitious systems; novel materials and technologies; testing and waste acceptance criteria; and modelling long term behaviour.
Enhanced Thermal Conductivity of Phase Change Materials Modified by Exfoliated Graphite Nanoplatelets
Authors: Xiang Jinglei , Drzal Lawrence
Published: April 2011

Composite phase change materials (PCM) were prepared by mixing exfoliated graphite nanoplatelets (xGnP) into paraffin wax. The two types of graphite nanoplatelets that were investigated were xGnP-1 having thickness of 10 nm and a diameter of 1 um and xGnP-15 having the same thickness with a platelet diameter of 15 um. Direct casting and two roll milling were used to prepare samples. Scanning electron microscopy images show that the nanofillers disperse very well in paraffin matrix without noticeable agglomeration. Paraffin/xGnP-15 PCM consistently exhibited higher thermal conductivity than xGnP-1 PCM. The improvement in thermal conductivity was as high as 5 fold for xGnP-15 composites and 2 fold for xGnP-1 composites at 4 vol%. The aspect ratio, particle orientation, and interface density between the conductive particles and the polymer matrix were found to be the critical parameters in determining the conductivities of the resulting nanocomposites. The thermal physical properties of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). It was found that the latent heat of nanocomposites was not negatively affected in the presence of xGnP particles and the thermal stability improved.
Piezoelectric vibration harvesting device with automatic resonance frequency tracking capability
Authors: Defosseux Maxime , Marzencki Marcin , Basrour Skandar
Published: April 2011

Further development in the area of vibration energy harvesting is limited by the lack of efficient methods to adapt the harvester to its surroundings. To this end, we propose an innovative passive way of automatic passive resonance frequency tracking.

We present a new approach employing mechanical non-linear behaviour of the system to track the vibration frequency peak. An analytical model representing these nonlinear harvesting systems has been developed and analysed. Experimental results obtained with custom fabricated MEMS devices show an experimentally verified frequency adaptability of over 36% for a clamped-clamped beam device at 2g (1g=9.81m.s-2) input acceleration. We believe that the proposed solution is perfectly suited for autonomous industrial machinery surveillance systems, where vibrations with high accelerations that are necessary for enabling this solution are abundant.
Characterization of the Corrosion Kinetic of X52 Steel in Seawater with Biocides
Authors: Galvan-Martinez R. , Orozco-Cruz R. , Torres-Sánchez R. , Martínez-Martinez E. A.
Published: April 2011

Corrosion study of the API X52 pipeline steel immersed in seawater without biocide and with 0.25, 0.5 and 0.75 ppm of biocide, under static and dynamic (turbulent flow) conditions was carried out at room temperature and atmospheric pressure. The hydrodynamic conditions were controlled by a rotating cylinder electrode (RCE) and the rotation speed was 1000 RPM. I order to analyse the corrosion process, linear polarization resistance (LPR), and polarization curves (PC) were made. This work investigation shown that the corrosion rate is higher under turbulent flow conditions than static conditions. A localized corrosion attacks was found in the superficial analysis.
Characterization of Strain Hardening Behavior and Residual Stress Induction Used For Crack Arrest in a Biocompatible Material
Authors: Urriolagoitia-Sosa G. , Molina-Ballinas A. , Urriolagoitia-Calderón G. , Hernández-Gómez L. H. , Sandoval-Pineda y J. M.
Published: April 2011

For centuries, the manipulation of mechanical properties for the development of components has been extremely important. Its relevance is based on improving the service life in the components. The aim of some techniques that have been used is to introduce strain hardening (tensile) and a beneficial residual stress field. Nevertheless, the application of both methods is very common when the component is manufactured, but the lack of knowledge of the final physical state of the material could compromise the structural integrity of the final product. This work presents a numerical evaluation concerning the characterization of a stainless steel AISI 316L, having a homogeneous axial history and a residual stress field. The relevance of the work is focused in a new methodology that can be used to improve the mechanical resistance of the component and to arrest crack propagation. By altering the mechanical properties of the material, it could be possible to delay nucleation and interrupt the propagation of cracks. This study also shows that if the strain hardening behaviour and the introduction of the residual stress field is not done properly, it could result in a component susceptible to fail. In the same sense, bending tests are proposed to provide tensile and compressive stress profiles.
Synthesis and Characterization of Nanoparticles of TiO2
Authors: Lima García Rosa M. , Quintero-Torres Rafael
Published: April 2011

The first steps in the synthesis of nanostructures are followed through UV-Vis and correlated with photoluminescence and images taken by SEM and TEM. Colloids permit the control in the atomic arrangement and the formation of nanostructures used to build cluster of materials. The size of the cluster in the colloid is around 5 nm. After the formation of the colloid a hydrothermal growth and microwave heating allows the formation of an ensemble of nano-sheet. This work is aim in the direction to controls the synthesis and the properties of materials with potential applications as active optical materials.
Preparation and Mechanical Properties of Polyethylene-Portland Cement Composites
Authors: L.P. Rivas-Vázquez , R. Suárez-Orduña , M. Valera-Zaragoza , De la L. Máas-Díaz A. , E. Ramírez-Vargas
Published: April 2011

The effects of waste polyethylene aggregate as admixture agent in Portland cement at different addition polyethylene/cement ratios from 0.0156 to 0.3903 were investigated. The reinforced samples were prepared according the ASTM C 150 Standard (samples of 5 × 5 × 5 cm). The reinforcing fibers were milling at a size of 1/25 in diameter, form waste and used them to evaluate the effects in mechanical properties in cement-based composites. The evaluation of polyethylene as additive was based on results of density and compression tests. The 28-day compressive strength of cement reforced with plastic waste at a replacement polyethylene/cement ratio of 0.0468 was 23.5 MPa compared to the control concrete (7.5 MPa). The density of cement replaced with polyethylene varies from 2.114 (0% polyethylene) to 1.83 g/cm3 by the influence of polyethylene.
Spectroscopy Analysis of the Ring Opening Reaction in Functionalized Spiropyran Films
Authors: Delgado-Macuil Raúl J. , Rojas-López Marlon , Gayou Valentín L. , Orduña-Díaz Abdu , Díaz-Reyes Joel , Camacho-Pernas Virginia
Published: April 2011

In this work we used the Fourier Transform Infrared spectroscopy and UV/Vis spectroscopy to analyze the behaviour of self-ensemble films of spiropyran when the films were irradiated by UV. In UV/Vis spectroscopy is possible observe the generation of the absorption peak, at 575 nm, associated to the merocyanine state when the ring-opening process is induced by UV light. In ATR the kinetics of the ring-opening was determinate too; following the spectra changes in real time.