Aumasson J.-P.,National Cooperative for the Disposal of Radioactive Waste |
Henzen L.,UBS AG |
Meier W.,University of Applied Sciences and Arts Northwestern Switzerland |
Naya-Plasencia M.,University of Versailles
Journal of Cryptology | Year: 2013
The need for lightweight (that is, compact, low-power, low-energy) cryptographic hash functions has been repeatedly expressed by professionals, notably to implement cryptographic protocols in RFID technology. At the time of writing, however, no algorithm exists that provides satisfactory security and performance. The ongoing SHA-3 Competition will not help, as it concerns general-purpose designs and focuses on software performance. This paper thus proposes a novel design philosophy for lightweight hash functions, based on the sponge construction in order to minimize memory requirements. Inspired by the stream cipher Grain and by the block cipher KATAN (amongst the lightest secure ciphers), we present the hash function family Quark, composed of three instances: u-Quark, d-Quark, and s-Quark. As a sponge construction, Quark can be used for message authentication, stream encryption, or authenticated encryption. Our hardware evaluation shows that Quark compares well to previous tentative lightweight hash functions. For example, our lightest instance u-Quark conjecturally provides at least 64-bit security against all attacks (collisions, multicollisions, distinguishers, etc.), fits in 1379 gate-equivalents, and consumes on average 2.44 μW at 100 kHz in 0.18 μm ASIC. For 112-bit security, we propose s-Quark, which can be implemented with 2296 gate-equivalents with a power consumption of 4.35 μW. © 2012 International Association for Cryptologic Research.
Strasser M.,ETH Zurich |
Monecke K.,Wellesley College |
Schnellmann M.,National Cooperative for the Disposal of Radioactive Waste |
Anselmetti F.S.,University of Bern
Sedimentology | Year: 2013
Central Switzerland lies tectonically in an intraplate area and recurrence rates of strong earthquakes exceed the time span covered by historic chronicles. However, many lakes are present in the area that act as natural seismographs: their continuous, datable and high-resolution sediment succession allows extension of the earthquake catalogue to pre-historic times. This study reviews and compiles available data sets and results from more than 10 years of lacustrine palaeoseismological research in lakes of northern and Central Switzerland. The concept of using lacustrine mass-movement event stratigraphy to identify palaeo-earthquakes is showcased by presenting new data and results from Lake Zurich. The Late Glacial to Holocene mass-movement units in this lake document a complex history of varying tectonic and environmental impacts. Results include sedimentary evidence of three major and three minor, simultaneously triggered basin-wide lateral slope failure events interpreted as the fingerprints of palaeoseismic activity. A refined earthquake catalogue, which includes results from previous lake studies, reveals a non-uniform temporal distribution of earthquakes in northern and Central Switzerland. A higher frequency of earthquakes in the Late Glacial and Late Holocene period documents two different phases of neotectonic activity; they are interpreted to be related to isostatic post-glacial rebound and relatively recent (re-)activation of seismogenic zones, respectively. Magnitudes and epicentre reconstructions for the largest identified earthquakes provide evidence for two possible earthquake sources: (i) a source area in the region of the Alpine or Sub-Alpine Front due to release of accumulated north-west/south-east compressional stress related to an active basal thrust beneath the Aar massif; and (ii) a source area beneath the Alpine foreland due to reactivation of deep-seated strike-slip faults. Such activity has been repeatedly observed instrumentally, for example, during the most recent magnitude 4·2 and 3·5 earthquakes of February 2012, near Zug. The combined lacustrine record from northern and Central Switzerland indicates that at least one of these potential sources has been capable of producing magnitude 6·2 to 6·7 events in the past. © 2012 The Authors. Journal compilation © 2012 International Association of Sedimentologists.
Lisjak A.,University of Toronto |
Grasselli G.,University of Toronto |
Vietor T.,National Cooperative for the Disposal of Radioactive Waste
International Journal of Rock Mechanics and Mining Sciences | Year: 2014
The stability of circular excavations in clay shales is a key issue in the drilling and tunnelling industries as well as in the field of deep geological waste storage. A large body of experimental evidence indicates that the damaged zone around these cavities is influenced by strong mechanical anisotropy induced by the layered material structure. The vast majority of numerical models adopted to date to analyse the stability of openings in layered rocks have been based on continuum mechanics principles using classic shear failure theory for elasto-plastic materials. However, a number of experimental observations demonstrate that clay shales may fail in a brittle manner under low-confinement conditions such as those characterizing the near-field of the excavation. Therefore, an alternative numerical approach based on non-linear fracture mechanics principles and the discrete element method is adopted to gain new insight into the failure process of this class of geomaterials. In order to account for the influence of clay shale microstructure on its mechanical behaviour a newly developed approach to capture the anisotropy of strength is proposed. With this numerical approach, the cohesive strength parameters of the fracture model are assumed to be a function of the relative orientation between the element bonds and the layering orientation. The effectiveness of the numerical technique is quantitatively demonstrated by simulating standard rock mechanics tests on an indurated claystone, namely Opalinus Clay. Emergent strength and deformation properties, together with the simulated fracture mechanisms, are shown to be in good agreement with experimental observations. The modelling technique is then applied to the simulation of the Excavation Damaged Zone (EDZ) around a circular tunnel in horizontally bedded Opalinus Clay. The simulated fracturing process is mainly discussed in the context of the damage mechanisms observed at the Mont Terri URL. Furthermore, the influence of in situ stress on resulting EDZ geometry is analysed together with possible implications for ground support and tunnel constructability. Modelling results highlight the importance of shear strength mobilization along bedding planes in controlling the EDZ formation process. In particular, slippage of bedding planes is shown to cause rock mass deconfinement which in turn promotes brittle failure processes in the form of spalling. The numerical technique is currently limited to two-dimensional analyses without any thermo-hydro-mechanical coupling. © 2013 Elsevier Ltd.
Labiouse V.,Ecole Polytechnique Federale de Lausanne |
Vietor T.,National Cooperative for the Disposal of Radioactive Waste
Rock Mechanics and Rock Engineering | Year: 2013
In the context of nuclear waste disposal in clay formations, laboratory and in situ simulation experiments were performed to study at reduced scale the excavation damaged zone (EDZ) around tunnels in the indurated Opalinus Clay at Mont Terri, Switzerland. In the laboratory, thick-walled hollow cylindrical specimens were subjected to a mechanical unloading mimicking a gallery excavation. In samples cored parallel to bedding, cracks sub-parallel to the bedding planes open and lead to a buckling failure in two regions that extend from the borehole in the direction normal to bedding. The behaviour is clearly anisotropic. On the other hand, in experiments performed on specimens cored perpendicular to bedding, there is no indication of failure around the hole and the response of the hollow cylinder sample is mainly isotropic. The in situ experiment at Mont Terri which consisted in the overcoring of a resin-injected borehole that follows the bedding strike of the Opalinus Clay showed a striking similarity between the induced damaged zone and the fracture pattern observed in the hollow cylinder tests on samples cored parallel to bedding and such a bedding controlled Excavation Damaged Zone is as well consistent with the distinct fracture patterns observed at Mont Terri depending on the orientation of holes/galleries with respect to the bedding planes. Interestingly, the damaged zone observed in the hollow cylinder tests on samples cored parallel to bedding and in situ around URL galleries is found to develop in reverse directions in Boom Clay (Mol) and in Opalinus Clay (Mont Terri). This most probably results from different failure mechanisms, i.e. shear failure along conjugated planes in the plastic Boom Clay, but bedding plane splitting and buckling in the indurated Opalinus Clay. © Springer-Verlag Wien 2013.
Sellin P.,Swedish Nuclear Fuel and Waste Management Company |
Leupin O.X.,National Cooperative for the Disposal of Radioactive Waste
Clays and Clay Minerals | Year: 2014
Geological disposal is the preferred option for the final storage of high-level nuclear waste and spent nuclear fuel in most countries. The selected host rock may be different in individual national programs for radioactive-waste management and the engineered barrier systems that protect and isolate the waste may also differ, but almost all programs are considering an engineered barrier. Clay is used as a buffer that surrounds and protects the individual waste packages and/or as tunnel seal that seals off the disposal galleries from the shafts leading to the surface. Bentonite and bentonite/sand mixtures are selected primarily because of their low hydraulic permeability in a saturated state. This ensures that diffusion will be the dominant transport mechanism in the barrier. Another key advantage is the swelling pressure, which ensures a self-sealing ability and closes gaps in the installed barrier and the excavation-damaged zone around the emplacement tunnels. Bentonite is a natural geological material that has been stable over timescales of millions of years and this is important as the barriers need to retain their properties for up to 106 y. In order to be able to license a final repository for high-level radioactive waste, a solid understanding of how the barriers evolve with time is needed. This understanding is based on scientific knowledge about the processes and boundary conditions acting on the barriers in the repository. These are often divided into thermal, hydraulic, mechanical, and (bio)chemical processes. Examples of areas that need to be evaluated are the evolution of temperature in the repository during the early stage due to the decay heat in the waste, re-saturation of the bentonite blocks installed, build-up of swelling pressure on the containers and the surrounding rock, and degradation of the montmorillonite component in the bentonite. Another important area of development is the engineering aspects: how can the barriers be manufactured, subjected to quality control, and installed? Geological disposal programs for radioactive waste have generated a large body of information on the safety-relevant properties of clays used as engineered barriers. The major relevant findings of the past 35 y are reviewed here.
Gaus I.,National Cooperative for the Disposal of Radioactive Waste
International Journal of Greenhouse Gas Control | Year: 2010
Before implementing CO2 storage on a large scale its viability regarding injectivity, containment and long-term safety for both humans and environment is crucial. Assessing CO2-rock interactions is an important part of that as these potentially affect physical properties through highly coupled processes. Increased understanding of the physical impact of injected CO2 during recent years including buoyancy driven two-phase flow and convective mixing elucidated potential CO2 pathways and indicated where and when CO2-rock interactions are potentially occurring. Several areas of interactions can be defined: (1) interactions during the injection phase and in the near well environment, (2) long-term reservoir and cap rock interactions, (3) CO2-rock interactions along leakage pathways (well, cap rock and fault), (4) CO2-rock interactions causing potable aquifer contamination as a consequence of leakage, (5) water-rock interactions caused by aquifer contamination through the CO2 induced displacement of brines and finally engineered CO2-rock interactions (6). The driving processes of CO2-rock interactions are discussed as well as their potential impact in terms of changing physical parameters. This includes dissolution of CO2 in brines, acid induced reactions, reactions due to brine concentration, clay desiccation, pure CO2-rock interactions and reactions induced by other gases than CO2. Based on each interaction environment the main aspects that are possibly affecting the safety and/or feasibility of the CO2 storage scheme are reviewed and identified. Then the methodologies for assessing CO2-rock interactions are discussed. High priority research topics include the impact of other gaseous compounds in the CO2 stream on rock and cement materials, the reactivity of dry CO2 in the absence of water, how CO2 induced precipitation reactions affect the pore space evolution and thus the physical properties and the need for the development of coupled flow, geochemical and geomechanical models. © 2009 Elsevier Ltd. All rights reserved.
Zuidema P.,National Cooperative for the Disposal of Radioactive Waste
Progress in Nuclear Energy | Year: 2015
In Switzerland, legislation and regulatory guidance are in place to ensure the implementation of deep geological repositories for all types of radioactive waste. A site selection process based on safety criteria, defined in the "Sectoral plan for deep geological repositories", will be followed by a step-by-step licensing process under the responsibility of the Federal Government. Stage 1 of the Sectoral Plan has been successfully completed and geological siting regions identified. Stage 2, currently underway, has included the participation of a wide range of stakeholder to identify sites for the surface facilities. It will lead to the narrowing down of the number of geological siting regions by means of a safety-based comparison. Key factors for successful site selection include: (i) A clearly defined stepwise approach with the criteria defined before starting site selection with first priority given to safety; (ii) a process in which all stakeholders are prepared to commit themselves and work together, and are ready to accept the basic rules defined beforehand; (iii) for this purpose, it is important to have a strong process owner who keeps the process on track. © 2015 Elsevier Ltd.
Aumasson J.-P.,National Cooperative for the Disposal of Radioactive Waste |
Bernstein D.J.,University of Illinois at Chicago
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012
SipHash is a family of pseudorandom functions optimized for short inputs. Target applications include network traffic authentication and hash-table lookups protected against hash-flooding denial-of-service attacks. SipHash is simpler than MACs based on universal hashing, and faster on short inputs. Compared to dedicated designs for hash-table lookup, SipHash has well-defined security goals and competitive performance. For example, SipHash processes a 16-byte input with a fresh key in 140 cycles on an AMD FX-8150 processor, which is much faster than state-of-the-art MACs. We propose that hash tables switch to SipHash as a hash function. © Springer-Verlag 2012.
Levasseur S.,University of Liège |
Charlier R.,University of Liège |
Frieg B.,National Cooperative for the Disposal of Radioactive Waste |
Collin F.,University of Liège
International Journal of Rock Mechanics and Mining Sciences | Year: 2010
A zone with significant irreversible deformations and significant changes in flow and transport properties is expected to be formed around underground excavations in indurated clay. The stress perturbation around the excavation could lead to a significant increase of the permeability, related to diffuse and/or localised crack propagation in the material. The main objective of this study is to model these processes at large scale in order to assess their impacts on the performance of radioactive waste geological repositories. This paper concerns particularly the hydro-mechanical modelling of a long-term dilatometer experiment performed in Mont Terri Rock Laboratory in Switzerland. The proposed model defines the permeability as a function of the aperture of the cracks that are generated during the excavation. With this model, the permeability tensor becomes anisotropic. Advantages and drawbacks of this approach are described using the results of the Selfrac long-term dilatometer experiment. © 2010 Elsevier Ltd.
News Article | February 15, 2017
"Radioactive waste containers are safer the deeper they are buried in rock, but that makes the process much more technically challenging too. I had to consider both of these factors in my thesis, while maintaining a very long-term perspective," says Valentina Favero, a civil engineer and a researcher in EPFL's Laboratory of Soil Mechanics (LMS) who passed her PhD oral exam on 16 January. Her public defense will take place on 3 March at EPFL. "Favero's findings will play a role in selecting radioactive waste storage sites in Switzerland," says Professor Lyesse Laloui, one of her PhD advisors and head of the LMS. "Her work is sure to have major scientific implications and a significant impact on society." In 2008, the National Cooperative for the Disposal of Radioactive Waste (Nagra) identified six regions in Switzerland, approved by the Federal Council, that could be used to store radioactive waste. Since then, the list has been whittled down to two regions – northeast Zurich and eastern Jura (Aargau) – on the basis of work done by Favero for her PhD. According to Favero, these two sites meet the safety and feasibility requirements of storing highly radioactive waste from Swiss nuclear power plants, as well as low-activity waste, which is produced by medical, research and engineering activities. But Favero's contributions do not end there: her research will also be used in a more detailed study of the sites approved by the Federal Council during the next step of the selection process. This study was granted financial support from Nagra. What was Favero's approach in her PhD? First, she learned more about the properties of Opalinus clay, which is the type of rock commonly used in Switzerland for storing radioactive waste. She studied the clay's characteristics at different depths in the six regions short-listed by Nagra. This was meticulous work, as the clay's properties vary with depth. Favero noted all of the clay's physical, mechanical and chemical features, and studied how the heat given off by radioactive waste containers affects both the clay and the materials (such as bentonite) used to surround the canisters – materials that may expand or contract in the presence of heat. She also identified the chemical composition of the liquid found in the clay's pores, since the composition may change in response to heat. She needed to investigate other hydraulic properties of rocks as well, including "suction", which refers to rocks decreasing in volume when they become partially saturated. In order to see the big picture – how these properties, taken together, could lead to radiation leaks – Favero had to crosslink her data. That was a laborious task, but it led to one of the key outcomes of her PhD. "The deeper you go, the more rigid and impermeable the rocks are. And that's exactly what we want – a solid barrier between us and the radioactive waste. But the technical challenges also increase the further down you go," says Favero. Even the process of drilling the tunnel that the radioactive waste containers will go through will affect how the surrounding rocks behave. This led Favero to analyze how the materials will react during the various phases of this process: "Rocks located at the upper end of the tunnel will be exposed to air," she explains. "That will lead to desaturation, in which some of the water held in the rocks evaporates. As they dry out, the materials could crack, which would make them more permeable. Yet we need impermeable rocks to achieve an effective seal." The researcher carefully studied this phenomenon and the related risks. Leaving no stone unturned, Favero also looked at the redistribution of forces when the tunnel is dug. This is called convergence, and it refers to the tunnel's tendency to collapse on itself. The deeper the tunnel, the greater the convergence. Favero's exhaustive research was instrumental in selecting the best two sites for storing radioactive waste in Switzerland and determining the safest and most technically feasible depth at which to place the steel canisters. More information: "Multiphysical behaviour of shales from Northern Switzerland", Valentina Favero. www.myscience.ch/events/id65382-multiphysical_behaviour_of_shales_from_northern_switzerland-swiss_federal_institute_of_technology_lausanne_epfl