Criteria and Conditions of Thermal Hydrodynamic Instability in the Circuits of Natural Circulation of Nuclear Power Plants in Case of Leak Accidents

Abstract

In today's extreme conditions of operation of nuclear power plants (NPP) of Ukraine, the need to improve systems and strategies for managing accidents with complete long-term blackout (CLTB) is especially urgent. A method of determining the conditions for the occurrence of thermal hydrodynamic instability (THI) in passive safety systems with natural circulation circuits (PSS NC) has been developed, based on the fundamental thermodynamic principles of analyzing the impact on stability of fluctuating deviations of pressure and mass flow of the working medium from the established (equilibrium) state. Using the examples of the small modular reactor (SMP) and the high power reactor (АР1000) of the Westinghouse company, the criteria and conditions of THI in accidents with leaks in the natural circulation circuits of the NPP are defined in a general format. The developed method of determining the criteria and conditions of THI in PSS NC can be applied by design, operating and regulatory organizations for deterministic analysis of the safety of NPPs of the AP/SMP type.