To assess the relevance of colloidal influences on radionuclide transport for the long-term safety of a radioactive waste repository, the KOLLORADO-2 project integrates the results of geochemical and hydrogeological studies. The results may serve as a basis for an appraisal of the implications of colloid presence in the vicinity of radioactive waste repositories in different deep geological host-rock formations.

This is the first book to cover actinide nano research. It is of interest both for fundamental research into the chemistry and physics of f-block elements as well as for applied researchers such as those studying the long-term safety of nuclear waste disposal and developing remediation strategies. The authors cover important issues of the formation of actinide nano-particles, their properties and structure, environmental behavior of colloids and nanoparticles related to the safe disposal of nuclear wastes, modeling and advanced methods of characterization at the nano-scale.

AECL Research is developing a concept for the permanent disposal of nuclear fuel waste in a deep engineered vault in plutonic rock of the Canadian Shield and is preparing an environmental impact statement (EIS) to document its case for the acceptability of the disposal concept. This report addresses the role of particles in radionuclide transport. It summarizes studies of natural particles in groundwater and presents the arguments used to justify the omission of particle-facilitated transport in the geosphere model that is based on the Whiteshell Research Area and used in the postclosure assessment study case.

Rock fractures can serve as water conducting structures for fluid flow and mass transport within the Earth's crust. Large apertures, which enable high flow velocities, and a rock matrix with several orders of magnitude lower permeability, are accountable that those structures serve as preferential conduits for solutes and colloids. The mechanistic understanding of fundamental transport and retention processes is essential to make reliable predictions of the fate of solutes and colloids in the subsurface. This comprehensive topic is of paramount importance in many areas of geo-engineering, for example disposal of nuclear waste in deep geological formations, enhanced geothermal systems, CO2 sequestration, gas and oil industry, and contaminant transport in groundwater systems. This cumulative Ph.D. thesis deals with the investigation of the impact of flow channel geometry on solute and colloid transport through natural rough fractures. The bottom-up approach used in this thesis helped to investigate separately the mechanisms and the processes on mass transport (solute and colloids) in four steps. All experiments in this thesis were conducted under hydraulic and chemical settings establishing laminar flow and overall unfavorable colloid attachment conditions.