Gudyma A. Improvement of beyond-design emergencies control strategies for nuclear safety of NPPs

The thesis research is dedicated to explosion-dangerous steam and gas compound formation peculiarities in closed technological environments and its impact on PWR reactors and their safety systems efficiency. This provides a basis for beyond-design control strategies improvement for increasing NPP and environmental safety. In contrast to known traditional approaches, generalized symptom-oriented method of effective beyond-design and severe emergencies control strategies formalization was applied. It's main content consists in considering actual state of safety barriers and environmental safety systems during environmentally hazardous sequence of emergency events development. Theoretical basis for thermodynamics criterial conditions for steam and gas explosions in PWR closed technological environments was given for non-stationary and non-equilibrium emergency sequence development. This conditions are applied to prevent or to minimize the environmentally hazardous radioactive substances emissions into the natural environment around the NPP. The generalized strategy for avoiding of steam and gas explosions was improved to optimize the efficiency of severe emergencies control. This is a prerequisite to provision of NPPs with PWR reactors environmental safety increase. The symptom-oriented approach to severe and beyond-design emergencies control strategies improvement was further developed to ensure NPPs environmental safety.