CRITERIA FOR CONDITIONS OF HYDRODYNAMIC INSTABILITY OF THE СOOLANT IN ACCIDENTS WITH REACTOR CIRCUIT LEAKS

Abstract

Modern deterministic codes for modeling the safety-dominant nuclear power plant accident groups with reactor circuit leaks (including inter-circuit leaks in steam generators) do not determine the conditions and consequences of the processes of hydrodynamic instability of the coolant. Work on preventing conditions of hydrodynamic instability was carried out for individual safety systems of the reactor installation in which specific equipment is installed. The occurrence of hydrodynamic instability of the coolant changes the conditions of heat exchange in the active zone of the reactor, leads to cyclic high-amplitude hydrodynamic loads on the internal body structures and other negative effects. The purpose of the presented work is to create methods for modeling conditions of hydrodynamic instability of the coolant during accidents with reactor circuit leaks. The method of implementation of the work is based on the development of a thermodynamic method for determining the conditions of hydrodynamic instability in the conditions of accidents with reactor circuit leaks. On the basis of the approximate method, the minimum dimensions of the reactor circuit leaks from the HPP in the area of hydrodynamic instability of the coolant were determined: for the emergency cooling system of the reactor active zone with high-pressure pumps - 400 mm; for the system of emergency cooling of the active zone of the reactor with low-pressure pumps - 100 mm. The occurrence of hydrodynamic instability of the coolant changes the conditions of heat exchange in the active zone of the reactor, leads to cyclic highamplitude hydrodynamic loads on the internal body structures and other negative effects. The original method of determining the criteria for the occurrence of hydrodynamic instability of the coolant at the stage of starting the pumps of safety systems in the event of an accident with reactor circuit leaks is presented.