Оцінка впливу гідродинамічної нестійкості перехідних режимів насосів систем безпеки під час аварій з міжконтурними течами на стан ядерних енергоустановок із ВВЕР

• Дата: 2022
• Автори: Kondratyuk, V., Pysmennyy, Yu., Skalozubov, V., Komarov, Yu., Kosenko, S.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: State Scientific and Technical Center for Nuclear and Radiation Safety 2022
• Онлайн доступ: https://nuclear-journal.com/index.php/journal/article/view/993
• Назва журналу: Nuclear and Radiation Safety

Based on operating experience, the results of monitoring the technical condition of a large number of heat exchange pipes in each steam generator, and the results of probabilistic safety analysis studies, an initiating event with inter-loop leaks is one of the dominant events. The technical difficulties of identifying inter-loop leaks, especially the rupture of a small number of SG heat exchange tubes, affect accident management strategies. During the implementation of emergency measures, as a result of pump startup, a transient may occur, which under certain conditions can lead to fluctuating hydrodynamic instability in the safety system trains, violation of heat exchange conditions in the reactor core, hydro- and thermodynamic shocks and other negative effects. When modeling accidents with deterministic codes, such a transient is modeled either simplified or is not considered at all. However, in pump startup transient modes, fluctuating hydrodynamic instability of the flow parameters may occur due to the inertial delay of the response of pump pressure-flow characteristics. In addition, the consumption in the safety systems in general can be affected by changes during a backpressure accident in the reactor and steam generators. On the basis of the conservative thermohydrodynamic model of an inter-loop leak accident, an original method for qualification of VVER nuclear power plants under hydrodynamic instability of pump startup transient modes of active safety systems is presented. The criteria for the impact of fluctuating hydrodynamic instability in pump startup modes of the emergency core cooling systems of the high and low pressure reactor, as well as the emergency steam generator makeup have been established to determine the conditions and consequences of hydrodynamic and thermal shocks. Hydrodynamic instability in the startup modes of safety system pumps under certain conditions significantly affects the pressure pulses of hydraulic shocks and the rate of temperature change for equipment metal during thermal shocks, which can affect the reliability and integrity of the systems. On the basis of calculation justifications according to the developed qualification method, the need to modernize active safety systems was determined to prevent fluctuating hydrodynamic instability in pump startup transient modes.