I can honestly say that I am very proud to get this opportunity to open this symposium and provide a few opening remarks on nuclear energy and nuclear waste management. I was once a nuclear chemist myself. Moreover, the Royal Swedish Academy of Engineering Sciences, IVA, has since her start in 1919 been concerned with all aspects of energy questions and energy politics but particularly in recent decades with the nuclear energy issues.

Nuclear power plays an important role in the Swedish power production. From this year on 45–50% of the Swedish electricity will be produced by nuclear power plants, the rest being hydro power.

The Crystalline Repository Project is responsible for siting the second high-level nuclear waste repository in crystalline rock for the United States Department of Energy. A methodology is being developed to define data and information needs and a way to evaluate that information. The areas of research the Crystalline Repository Project is involved in include fluid flow in a fractured network, coupled thermal, chemical and flow processes and cooperation in other nations and OECD research programs.

The United States has been engaged in defense nuclear activities for over 40 years. The primary goal of the Defense Waste and Byproducts Management Program is to develop technology which ensures the safe, permanent disposal of all defense nuclear waste. Programs are in place at each U.S. Department of Energy site which address long-term strategy for permanent disposal of waste generated as a result of defense operations. Technology is developed for assessing the hazards, environmental impact, and cost of each long-term disposition alternative for selection and implementation. This paper addresses the key research areas and major facilities associated with the long-term management of defense nuclear waste.

The most important aspects of this research program concern disposal safety: the long-term behavior and sensitivity of the materials to the variability inherent in industrial processes, and the characterization of the final product. This research required different investigations involving various scientific fields, and implements radioactive and non-radioactive glass samples as well as industrial scale glass blocks. Certain studies have now been completed; others are still in progress.

Based on more than 10 years of research and development, vitrification and high level waste disposal have reached the status of demonstration projects in the Federal Republic of Germany: hot operation of the PAMELA vitrification plant is scheduled for october 1985, and a disposal test with 30 canisters of high active glass is being prepared in the ASSE salt mine. Safety studies for a model repository led to a good understanding of the relevant phenomena; they will continue using sitespezific parameters. Modelling and computer codes will be further developed in international cooperation. In addition to reprocessing, the technology for direct disposal of spent fuel will be developed and demonstrated in the next years.

The increased emphasis put upon disposal of HLW in recent years led to the growth of large numbers of research programmes in many countries. Many results of this research have flowed into projects developing and analysing geologic repository concepts; the basic feasibility of implementing safe disposal facilities is now generally accepted by the technical community (though not always by the public!)

The Canadian Nuclear Fuel Waste Management Program is reviewed, illustrating the progress that has been made in assessing the concept of disposal of nuclear fuel waste in plutonic rock of the Canadian Shield. Research is being conducted into used fuel storage and transportation, fuel waste immobilization, site characterization and selection methods, and performance assessment modelling. Details of achievements in these areas are outlined, and results of the most recent interim assessment are discussed.

The diffusion of non-sorbing species in different crystalline rocks and fissure coating materials has been studied. The results show that the effective diffusivity of iodide, Uranine and Cr-EDTA in rock materials with fissure coating material is of the same magnitude or higher than in granites and gneisses. The results also show that it is not possible to assign one value to the diffusivity of a rock from a given area. The variations in properties are too large. The estimated effective diffusivity of iodide in rocks without fissure coating material was found to be in the range 1.10-14 m2/s to 70.10-14 m2/s.

To simulate the stress that exists in the bedrock at large depths, diffusion experiments with iodide and electrical resistivity measurements in rock materials under mechanical stress have been performed. It was found that the diffusivity in rock samples at 300–350 bars stress was reduced to 20–70% of the value in samples under atmospheric pressure.

Distribution ratios have been determined for Sr, Cs and Tc (as pertechnetate) over a range of concentrations for a Darley Dale sandstone by three different methods: crushed rock batch tests, with W/R ratio and particle size range as independent variables, diffusion-sorption and permeability-sorption experiments on intact rock samples. Comparisons of Rd - values obtained from batch and diffusion-sorption experiments indicate that crushed rock tests can overestimate sorption by as much as one or two orders of magnitude.

Concentrations and isotope ratios of natural decay series radionuclides have been studied in three contrasting crystalline rock drillcore sections intersecting water-conducting fractures deep in the bedrock. Radioactive disequilibria resulting from rock-water interactions were observed in two of the cores. These indicated uranium migration along distances of 40 cm or more on a timescale of 106 years in conjunction with thorium immobility under the same conditions. Fracture surface minerals showed a high affinity for radionuclide retardation and a limit of about 3 cm is suggested for the migration of radionuclides from fracture fluids into the saturated rock. This limit may correspond to enhanced matrix porosities resulting from earlier hydrothermal activity along the same channels.

Atomic Energy of Canada Limited is studying the disposal of nuclear fuel-waste in a vault in plutonic rock. An important part of this study is to develop models to assess the rate of escape of waste components to the biosphere. In these models time-dependent changes in the system are important. One such change is the increase in temperature of the rock mass immediately surrounding the vault, and in the far-field. Differential- thermal expansion between rock constituents (crystals), and the expansion of trapped water, will produce microcracking and, hence, possibly changes in intact-rock elastic modulus and permeability. This paper describes the model devised to estimate the extent of microcracking in rock surrounding a vault, and the anticipated changes in rock elastic modulus and permeability. The model is applied to a possible vault, located at various depths in plutonic rock typical of the Canadian Shield. It estimates the dimensions of an envelope outside of which the influence of the vault on microcracking will be negligible.

Two hydrogeologic conceptual models have been developed to describe the ground-water flow regime in the crystalline rocks of northern Switzerland. The purpose of these models has been to characterize the regional and local ground-water flow systems and to define the groundwater travel paths and velocities from potential waste disposal areas to the biosphere. Several parameters have been used as validation tools in the modeling process. These include potentiometric data, volumetric discharge rates, infiltration rates, bulk and isotopic geochemistry, and temperature distributions. The results of utilizing these validation tools are described.

Confidence in solutions of flow through stochastically generated hard rock formations was studied with the aid of a simplified synthetic model. The formation is conceptualized as a fracture network intersecting an impervious rock mass. The geometrical properties of the fracture network were assumed to be known while fracture transmissivities were considered a stochastic process.

First, network fracture transmissivities were generated using a given probability distribution function. This a priori model was considered the “true formation”. In a second step, only a limited amount of information, similar to that obtained in reality from boreholes, was used to construct a conditioned-by-measurement model.

Identical flow tests were performed on a formation constructed with limited data and on the “true formation”. The ratio of the rates of flow resulting from these tests was considered a measure of confidence in the stochastically generated formation. The results, with this model and a particular data set, show uncertainty values between 47% to 63%, corresponding to fracture sample sizes of 11% and 2% respectively, from the total number in the network.

Hydrothermal rock-water experiments at 80°, 150° and 250° C have been carried out to investigate the origin of saline groundwaters in the Carnmenellis Granite, Cornwall, UK which have previously been attributed to be derived via dissolution of biotite and plagioclase feldspar by dilute meteoric groundwaters. The nature of product fluid and solid phases in the experiments was dominated by the dissolution of plagioclase and potassium feldspars, coupled with the precipitation of laumontite, calcite and smectite. However, the release of chloride from the rock was minimal, suggesting minor dissolution of the major chloride bearing mineral, biotite. The relative inertness and stability of biotite during the experiments was borne out by direct physical observation of reacted biotites and by consideration of the fluid phase composition in terms of thermodynamic mineral stability diagrams. It is concluded that the experimental and natural systems are buffered under different chemical conditions, which may be due to acidity generated via oxidation of localised sulphide zones within the granite and absent in the experiments. Dissolution of biotite may be an important mechanism for enhancing the salinity of groundwaters in granitic rocks if groundwaters are buffered to be outside the stability of biotite and convective circulation is significant.

The modelling of water flow in the bedrock is of especial importance for safetyassessementof radioactive waste disposal in crystalline rocks. Age dating of the water has been tried for the validation of ground water transport models. Thus, several tritium and 14C-analyses have been carried out on water samples from deep boreholes drilled within SKB's (Swedish Nuclear Fuel and Waste Management Company) study sites. However, several processes will influence the final content of 14C in the groundwater measured and correction for enrichment and dilution are hard to carry out. Another contribution to the understanding of recharge water transport by using frequency and stable isotope analyses of calcite fissure fillings is suggested.

Deep groundwaters from sites potentially suitable for the disposal of spent nuclear fuel have been chemically characterized. The waters are classified according to their contents of main constituents and pH as shallow or deep groundwaters. New equipment consisting of a mobile field laboratory and downhole pH and Eh probes has been successfully used in the investigations.

The deep groundwaters contain appreciable amounts of iron and sulphide and Eh values monitored downhole are more negative than those obtained from calculations based on the ferrous iron ferric hydroxide system. Laboratory simulations of the water rock interaction indicate that the dissolved oxygen is quickly removed when the water is in contact with the rock.

A borehole pulse radar system has been developed as part of the International Stripa Project with the objective to identify and characterize fracture zones at a considerable distance from boreholes. The radar uses very short pulses, which are transmitted and received by dipole antennas inserted into the boreholes. The pulses are extremely broadband with center frequencies of 25–60 MHz corresponding to wavelengths of a few meters in the rock. At 25 MHz the attenuation in the Stripa granite is 28 dB/100 m and the pulse velocity is approximately 128 000 km/s. Reflection measurements have been used to identify fracture zones and determine their position and orientation. The zones often cause strong and well-defined reflections. Improvements in the pulse form and numerical filtering of the data have consequently made the radar a very efficient instrument for locating fracture zones. During measurements in Stripa reflections from fracture zones have been observed more than 100 m from the borehole.

The results from a large number of single-hole packer tests in crystalline rock from three test sites in Sweden have been analysed statistically. Average hydraulic conductivity values for 25 m long test intervals along boreholes with a maximal length of about 700 m are used in this study. A comparison between steady state and transient analysis of the same test data has been performed.

The mean vaule of the hydraulic conductivity determined from steady state analysis was found to be about two to three times higher compared to transient analysis. However, in some cases the steady state analysis resulted in 10 to 20 times higher values compared to the transient analysis. Such divergence between the two analysis methods may be caused by deviations from the assumed flow pattern, borehole skin effects and influence of hydraulic boundaries.

The OECD Nuclear Energy Agency is coordinating the development of a critically reviewed CODATA compatible chemical thermodynamic data base for ten radioelements important to various areas of nuclear technologies. Such a data base in itself is insufficient for modeling the speciation and solubility behaviour of radioelements in natural rock/water systems. Data must also be available for describing the rock phases present, which determine to a large extent the physico-chemical environment. Since a number of NEA Member countries are contemplating nuclear waste disposal in granitic environments, a data base for seventy-three minerals associated with granite is presented here, as a complement to the data base work on radioelements.