Recent Domestic Research Trends of Natural Circulation Behaviors for Nuclear Reactor Safety

In order to assess the cooling ability, many studies have been conducted to assess passive means of reactor core cooling. One of key factors for these studies is to generate driving force for coolant flows without supplying electrical energy. In Heavy Water Reactor (HWR) including CANDU, the research topic is also very important because there is still a concern about core cooling in case of SBO accident at HWRs. In order to overcome the difficulty, natural circulation phenomena can be an answer because they are simply happened by density differences of a fluid. However, natural circulation flow in HWRs can be established hard because HWRs have horizontal fuel channels and these channel configurations result in considerable friction loss compared to vertical geometries. In this paper, major phenomena of SBO accident in CANDU are introduced and recent domestic research trends of natural circulation for a variety of reactor types are summarized. The previous studies are mainly focused on the vertical flow of natural circulation, while few studies have been made for horizontal natural circulation flow. Based on the previous studies, a numerical study on natural circulation flow in horizontal channels will be conducted in the future work.