Ricardo Juncosa

Final Disposal of the Wastes Associated with the Oil Spill of the Tanker Prestige through its Stabilization with Quicklime and Granite Fines

The sinking of the tanker Prestige produced a large oil spill that affected the shores of Spain, Portugal and France. Cleaning operations were performed on the sea and the coasts and the waste recovered was a mélange of fuel, water and a variety of debris. Waste mass balances show that, while the total amount of recovered fuel is close to the amount spilled by the vessel, the total amount of waste is about four times that quantity. In the present study we have focused in the stabilization of the raw oily wastes of the Prestiges oil spill using quicklime and granite sawdust, which is an inert waste of the local dimension stone industry. Given appropriate proportions of quicklime and sawdust, stabilization is feasible and provides a better performance than the only use of quicklime. Leaching tests indicate that the stabilized mixtures can be considered a non-dangerous waste although high quicklime contents may enhance the leachability of given components (Ba, Cr, SO 4 ) and BTEX. For the purpose of landfill disposal, sawdust-bearing stabilized mixtures have an acceptable geotechnical behavior and no evidence has been found suggesting the eventual destabilization of the mixtures and/or its fluidification/liquation.

Hydrochemical characteristics of the natural waters associated with the flooding of the Meirama open pit (A Coruña, NW Spain)

Abstract In December, 2007, after 30 years of operations, the mine of Meirama ceased extraction of brown lignite. Since then operations have begun which will lead to the formation of a big mining lake (~2 km2 surface and up to 180 m deep) after controlled flooding of the open pit. In the process of flooding, both surface and ground waters are involved, each with their own chemical signature. According to the information available, the diversion of surface waters towards the pit hole should lead to the formation of a water body of acceptable quality. However, an unassisted flooding process could eventually form an acidic lake.

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

FEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

Improvements in Mero River Basin Water Supply Regulation Through Integration of a Mining Pit Lake as a Water Supply Source

Seasonal increases in demand puts a strain on water supplies in the city of La Coruña (northwest Spain) and its surroundings during times of drought. Exploitation of Meirama Lake, a pit lake forming in a former lignite mine, could supplement the Abegondo-Cecebre reservoir, the city’s main water supply. We analysed the hydrochemistry and the Mero River basin regulations to determine whether the water quantity and quality could meet the needs during periods of increased demand and drought, and still satisfy ecological conditions required by law. Our results indicated that joint use of the two reservoirs is feasible. The local administration is implementing the recommendations by building a tunnel to tap into the pit lake.ZusammenfassungSaisonale Steigerungen des Wasserbedarfs während Trockenperioden belasten die Wasserversorgung in der Stadt La Coruna (Nordwestspanien) und deren Umland. Durch die Erschließung des Sees Meirama, einem Bergbaufolgesee des Braunkohlenbergbaus, konnte die Hauptwasserversorgung der Stadt durch die Abegondo-Cecebre-Talsperre ergänzt werden. Wir untersuchten die Hydrogeochemie und die Steuerung des Wasserdargebots des Flusses Mero, um zu prüfen, ob die Ansprüche an die Wassermenge und –qualität während Zeiten mit erhöhtem Wasserbedarf bzw. Trockenheit und bei gleichzeitiger Einhaltung ökologischer Bedingungen nach Gesetzeslage erfüllt werden können. Unsere Ergebnisse deuten darauf hin, dass die gemeinschaftliche Nutzung beider Wasserreservoire möglich ist. Die lokale Verwaltung baut derzeit einen Tunnel, um den Bergbaufolgesee anzubinden und damit die Empfehlungen zur Steuerung der Wasserversorgung umzusetzen.ResumenLos incrementos estacionales en la demanda provocan dificultades en el suministro de agua en la ciudad de La Coruña (noroeste de España) y sus alrededores durante tiempos de sequía. La explotación del lago Meirama, un lago formado en el hueco de una antigua mina de lignito, podría suplementar el embalse de Abegondo-Cecebre que es la principal fuente de agua de la ciudad. Hemos analizado la hidroquímica y las regulaciones de la cuenca del río Mero para determinar si la cantidad y calidad del agua podría satisfacer las necesidades durante los períodos de demanda creciente y sequía y satisfacer las condiciones ecológicas requeridas por ley. Nuestros resultados indicaron que el uso compartido de ambos reservorios es factible. La administración local está implementando las recomendaciones construyendo un túnel para aprovechar el lago del hoyo de mina.总结旱季季节性需水增长加重了拉科鲁尼亚市(La Coruña)及其周边地区(Northwest Spain)供水压力。由褐煤开挖形成的Meirama采坑湖水可作城市供水Abegondo Cecebre水库的补充水源。分析了采坑湖水化学特征及Mero流域管理要求,研究了采矿湖水水质和水量是否满足干旱期需水要求及法律规定的生态要求。研究结果表明两水库水联合调度是可行的。当地政府已采纳建议并修建一条通向采坑湖的输水通道。

MODELING OF THE THERMOHYDRODYNAMIC AND REACTIVE BEHAVIOR OF COMPACTED CLAY FOR HIGH-LEVEL RADIONUCLIDE WASTE-MANAGEMENT SYSTEMS

Bentonite is often proposed as an engineered-buffer material in high-level radionuclide waste-management systems. For effective design of the barrier that will provide protection over the long time periods required, the physical/thermal/chemical processes taking place in the barrier material must be understood thoroughly. These processes, which interact, include the flow of water and gas, the flow of heat, and the transport and reaction of chemical constituents. The purpose of this study was to better understand the processes that occurred in a small-scale experiment within a confined bentonite space. A conceptual and mathematical model (FADES-CHEM) was built in order to simulate the results of an experiment conducted in 2000, and thereby to gain a better understanding of the controlling processes. In that experiment, a block of compacted bentonite was placed in an air-tight cell and subjected, for 6 months, to simultaneous heating and hydration from opposite sides. The bentonite block was then sliced into five sections each of which was then analyzed in order to obtain a series of physicochemical parameters illustrating the changes that had occurred. Before modeling, the chemical composition of the bentonite pore waters was restored in order to account for different processes such as gas outgassing and cell cooling. Modeling indicated that gas-pressure build up was a relevant process when computing the saturation of bentonite, and the computations in the present study suggested that evaporation/condensation processes played a crucial role in the final distribution of the water content. Gas pressure and evaporation/ condensation also affected the geochemical system, and the numerical model developed gives results that were consistent with the experimental values and trends observed. The model reproduced the results obtained and enable use at the repository scale and over longer time frames, provided that adequate data are available.

Ion Exchange Behavior of the Febex Bentonite: 2. Batch Experiments and Geochemical Modeling

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