Simulation investigation on flashing-induced instabilities in a natural circulation system

Flashing-driven natural circulation techniques have been widespreadly applied in advanced reactor designs due to its prominent advantages in the aspects of high reliability, cost-efficiency and inherent safety. However, flashing-induced instability probably occurs under certain conditions in a flashing-driven natural circulation system, which deserves comprehensive illustration. By using RELAP5 code, the behavior of a two-phase natural circulation system is investigated based on the experiment benchmark. Three instability flow modes formed by two typical flow instability mechanisms, along with stable single-phase flow and stable two-phase flow are identified and analyzed in this work. The effects of typical thermal boundaries and structural parameters on the instability thresholds are revealed as well. (C) 2020 Elsevier Ltd. All rights reserved.