The monograph presents the fundamentals and results of mathematical simulation of transient thermal hydraulic processes occurring at the Ignalina NPP compartments during the loss of cool-ant accidents. The building structures of the compartments constitute the last barrier for the fission products to enter the environment. The maintenance of this barrier's structural integrity in case of any initial event is one of the nuclear power plant's safety insurance tasks. The integrity of the structures during accidents is defined by the behavior of the thermal hydraulic parameters in the...