Basic research contributes to the advancement of science in the fields of fluid mechanics, heat transfer, nuclear and process engineering, probability theory and statistics, and fracture mechanics. THERMAL-HYDRAULIC SAFETY ANALYSES Results in the field of thermal-hydraulic safety analyses contribute to the research of following topics: - heat transfer in single-phase turbulent flow, - dispersion of the interface in stratified pipe flow, - partitioning of wall heat flux and flow structure evolution in subcooled boiling in vertical channels, - coupling of descriptions of two-phase dispersed flow at different length scales, - fine fuel fragmentation during steam explosion, - mechanisms of turbulent natural convection, - aerosol condensation and deposition in saturated atmosphere, - thermal stratification of multicomponent atmosphere, - water hammer in piping systems, - uncertainty evaluation of simulated transients in complex systems. PROBABILISTIC SAFETY ASSESSMENT The new method for improvement of computerized safety-related systems reliability integrates software development methods with fault tree analysis as a safety analysis method, which contains formal notation in its logically connected gates and in its basic events. The transformation of static fault tree into a dynamic fault tree is performed with a matrix of house events, which enables the consideration of time in models. The integration of mathematical model of probabilistic safety assessment and optimization method enables optimal scheduling of standby safety equipment based on minimal risk. The method for including linguistic input data in probabilistic models of components represents a new approach for assessing component states and represents a development in the integration of probability theory and fuzzy logic. STRUCTURAL SAFETY ANALYSES Research results contribute to the understanding and modeling of deformations and damage of metallic materials with special emphasis on those, which mainly develop between and due to crystal grains. The research is connected with state-of-the-art projects in the field of multiscale modeling of material behavior. A clear understanding of processes, which take place on a variety of scales ranging from atoms to macroscopic engineering sistems, is necessary for accurate predictions of material response to loading and ageing.