Objetivo Clays are proposed as engineered barriers for radioactive waste in many European countries and safety analyses based on assessment of their performance are under way. Such analyses indicate that dense smectite clay provides a practically impermeable embedment of waste canisters which means that radionuclides will only move by diffusion. The mechanisms involved in such transport and the diffusive transport capacity are poorly known, however, and the value of smectite clay as barrier can therefore not be fully assessed until there is better understanding of their performance, which the project is expected to give. The key factors are the physico/chemical properties of the smectite minerals and their spatial organisation with special respect to the physical state and composition of the porewater. These factors combine to yield the microstructural constitution of the clay which is known to be a function of the bulk density, dominant cation and temperature and which controls the retention and penetration of radionuclides. This means that the groundwater chemistry of the surroundings, i.e. the host rock or clay strata as well as the radionuclides and various species released from the smectite minerals, have an effect on the tightness of the clay barrier. This will be described in terms of the microstructure with special respect to radionuclide transport. Special attention will be paid to organophilic bentonites, i.e. smectite clays that are pretreated with certain organic substances. They have been found to sorb cations and high amounts of anions (iodine) as well. Preparation of organo-bentonites will be optimized towards retention of cations and anions according to the chemical spectrum of the relevant radionuclides contained in the waste material. Key data of the properties will be processed for incorporation into the nuclide diffusion model. The work will comprise both theoretical and experimental studies, the common basic components being the microstructure and the chemical characterization of the bentonites used, which will be modeled such that the influence of density, organic pretreatment, porewater chemistry and temperature on the retention and penetration of radionuclides can be quantified. With help of the model, necessary data for the evaluation of the performance of clay barriers and guidelines for their practical realization will be obtained. The models developed for predicting radionuclide retention and transport in the cationic and anionic forms will serve as necessary instruments in the design of repositories as well as for safety assessment. They will hence be of significant assistance in the European work to deal with the issue of effective and safe isolation of radioactive waste. Programa(s) EAEC-NFS 2 - Specific research and training programme in the field of nuclear safety and safeguards, 1994-1998 Tema(s) 030304 - Geomechanical behaviour of engineered materials and host rocks Convocatoria de propuestas Data not available Régimen de financiación CSC - Cost-sharing contracts Coordinador CLAY TECHNOLOGY AB Aportación de la UE Sin datos Dirección Ideon Research Centre Ole Roemers vaeg 12D LUND Suecia Ver en el mapa Coste total Sin datos Participantes (3) Ordenar alfabéticamente Ordenar por aportación de la UE Ampliar todo Contraer todo Kungliga Tekniska Hogskolan Suecia Aportación de la UE Sin datos Dirección 56,Tenikringen 100 44 Stockholm Ver en el mapa Coste total Sin datos Technical Research Centre of Finland Finlandia Aportación de la UE Sin datos Dirección 4B,Tekniikantie 4B 2044 Espoo Ver en el mapa Coste total Sin datos UNIVERSITAET HANNOVER Alemania Aportación de la UE Sin datos Dirección Am Kleinen Felde 30 30167 HANNOVER Ver en el mapa Coste total Sin datos
