ИСТИНА

Radioactive wastes disposal is a quite difficult and demanding technological process. The most hazardous types of solid and liquid radioactive wastes are primarily exposed to solidification and then to underground disposal. However, this approach to big volumes of the low- and mid-level radioactive wastes is not reasonable in most cases. Liquid radioactive wastes are basically complicated solutions of different pH with a significant amount of unstable isotopes. Obviously they can make a significant influence on a geological environment. Clay minerals are the most chemically reactive component of a geological environment; therefore they become affected by the influence of active solutions. The analysis of the possible transformations and synthesis of the new mineral phases makes it possible to predict migration process of the hazardous substances. The present research is based on the investigation of clay minerals, extracted from sandy reservoir beds for low-level radioactive wastes. Samples for the study were collected at a safe distance from the radioactivity affected area. The research object is the influence of different level acidity and alkalinity solutions on the geological environment. One of the most important instances is the evaluation of possible transformations due to the interactions between rock and solutions and distinction of them from naturally occurring geological processes. As a result of the work following changes of reservoir rock were revealed. First of all it concerns occurred in abundance process of leaching and synthesis of swelling (smectitic) clay minerals. Also it was found that well-sorted sands provide enabling environment for smectite synthesis. This observation can be explained by better permeability of such sands which leads to more efficient supply of material for reaction. Clay fraction detailed study gave us the information to distinguish neocrystallization due to catagenesis which were taking place in reservoir and buffer horizons. However on the background of naturally occurring processes some technologically induced alterations were found. It concerns neocrystallyzed smectite, for which morphological features, crystal-structure particularities and stages of growth were described. The obtained results allow us to suggest that isolation property of geological environment in the waste site remains sustainable. Feldspar and dark-colored minerals' leaching may cause increase permeability, however new formations of smectite aggregates in big pores most probably will neutralize this effect.