[en] Information about the impact of faults and fractures on permeability of argillaceous formations has been collected by reviewing data provided by people involved in the excavation of deep tunnels. It appears that the fracture response and the secondary permeability of clay masses are characterized by a wide variability, due to the many factors at play. The Italian blue clays of plio-pleistocenic age can be intersected by water-bearing fractures. Other argillaceous formations present in Italy should also be considered for the disposal of radioactive waste. In particular, the widespread formation known as 'argille scagliose', despite the often chaotic structure and the presence of exotic materials, is homogeneous, from the viewpoint of hydraulic conductivity, and is rather promising as host rock of a radioactive waste repository. Work has been performed under contract with ENEA in the framework of the European Atomic Energy Communities cost-sharing research programme on 'Radioactive Waste Management and Disposal'. (Auth.)

[en] In the Federal Republic of Germany the waste management concept is based on disposal of all radioactive wastes in repositories in deep geological formations. In the repository the wastes are isolated from the biosphere by a system of multiple engineered and natural barriers. The raw wastes have to be transferred into an appropriate physical and chemical form to produce waste packages which satisfy the requirements of transport, handling, interim storage and disposal. Waste packages will have high chemical and mechanical stability and low volumes relating to the primary waste volume. From the great number of different low level and intermediate level waste types, this paper focusses on wastes from operation and decommissioning of nuclear power plants and from reprocessing of spent LWR-fuel. (Auth.)

[en] Long-term isolation of radioactive waste can be provided by a combination of natural and man-made barriers. Geological formations of different types have been proposed as suitable natural barriers for radioactive waste isolation. Argillaceous formations can have very favourable characteristics such as: low permeability, high sorption capacity, high plasticity. The retention properties and the low intrinsic permeability can guarantee waste isolation as long as the rock is homogeneous and integer. The presence of undetected fractures, or fractures formed after waste emplacement, can seriously compromise the efficiency of the barrier. In general terms clay formations are expected to respond in a plastic way to external stresses, thus fault and fracture formation should be a rare phenomenon in such media. This plastic behaviour seems supported by mathematical models applied to both conceptual and specific cases. Nevertheless, faults and fractures have been observed in clay outcrops, in quarries and in relatively deep tunnels. In some quarries, fissures surrounded by oxidation zones 1 or 2 cm thick have been seen. The mechanisms of fault and fracture formation in clays must be investigated and the possibility that they can act as pathways of enhanced water and radionuclide migration must be evaluated. (Auth.)

[en] Code of Federal Regulations restrictions make it possible to predict the maximum dose equivalent to an individual along the path of a passing spent fuel transport vehicle. These calculations utilize cylindrical geometry and include air attenuation and buildup but neglect individual shielding. The dose equivalents tabulated vary from 1.2 x 10^-4 mrem for a transport vehicle moving at 55 mph at a distance of 100 feet to 2.10 x 10^-3 mrem for a transport vehicle moving at 10 mph at a distance of 35 feet. The calculations may be duplicated on micro-computer systems. (Auth.)

[en] Simulated spent ion-exchange resin, labelled and inactive samples, have been immobilized by transforming them into homogeneous monolithic forms. Immobilization was achieved by incorporating the ion-exchange resin into an inert polymer matrix (namely, phenol-formaldehyde polymer) aimed at lowering as much as possible the release of radionuclides to the environment. The suitability and range of applicability of phenol-formaldehyde to immobilize various types of resins having different levels of activity were determined by studying the homogeneity, mechanical, thermal and chemical properties of the final solid products. Factors such as water content and mesh size of the incororated resins, type of leaching solution, coating and irradiation effects of the final products have also been investigated. (Auth.)

[en] In 1977 the West German Federal Minister for Research and Technology combined into one project a number of research efforts concerning the safety aspects of the nuclear waste disposal concept in the Federal Republic of Germany. The individual projects had already been conducted, or were in preparation, at various German universities, major research facilities, and industrial companies. The overall project was then designated 'Safety Studies for Nuclear Waste Management'. This project is a research activity which is not directly connected with official legal approval procedures involving nuclear waste and its final disposal at particular locations in the Federal Republic of Germany. In the development of the Safety Studies models and calculation techniques, however, work was conducted in such a manner that later implementation of the methods developed in the Safety Studies project would be possible. (Auth.)

[en] Natural zeolite Analcime has been considered as a possible sorbent and storage material for tritiated water. The kinetics of tritiated water release from analcime crystals of two size fractions (20-50 and 50-80 μm dia.) into surrounding water has been investigated at 25-60 ⁰C. At 25 ⁰C the half-life of THO/H₂O exchange for the smaller and larger beads is about 1.3 and 5.0 hours, respectively. This is higher than the corresponding results obtained with synthetic analcime, but still of the same order of magnitude. The difference is ascribed to the presence of mineral impurities in natural analcime. If the natural mineral could be processed into particles of 2-5 mm radius, that material might be useful as a storage for tritiated waste water. 6 refs.; 3 figs

[en] A numerical model predicting the rate of uniform corrosion of a steel canister for intermediate level nuclear waste surrounded by concrete in an underground repository is described. This model uses experimental data of the kinetics of various electrochemical reactions, which are obtained using fairly simple polarization methods and predicts actual metal wasteage rates. It considers the electrochemistry, solution chemistry and diffusion processes occuring in the vicinity of the metal surface. The model has been tested previously against experimental results for steel corroding in a solution at lower pH with reasonable success. Corrosion rates in concrete are estimated in the range 7 x 10^-2 - 2 x 10¹ μm/year, depending on the diffusivity of oxygen. These results agree well with experiment. (Auth.)

[en] A thermal model for explaining and simulating temperature distributions in glass solidified radioactive waste is proposed. Four operations of waste management have been considered: a) Cooling of a cylindrical matrix with current air. b) Cooling of a cylindrical matrix under water. c) Cooling of a buried cylindrical matrix in a geological repository (granite). d) Cooling of several arrangements of matrices in a geological repository (granite). (Auth.)

[en] A tracer breakthrough curve (BTC) usually has a tailing effect that cannot be explained by the conventional dispersion-advection model. In this study, the chemical, biological and physical mechanisms for the BTC tailing are discussed. Models developed in the recent literature to solve the BTC tailing effect were reviewed and compared. A general group transfer model developed herein extends the conventional dispersion-advection model to include concepts of mobile-immobile pores and nonequilibrium adsorption-desorption in nonhomogeneous media. This general group transfer model was combined with a nonlinear regression program to identify effective hydrogeologic parameters from experimental BTCs obtained in both homogeneous and nonhomogeneous media. (Auth.)