Fork-end heat pipe for passive air cooling of spent nuclear fuel pool

• DOI: 10.1016/j.nucengdes.2021.111081
• Publication Date: 2021-02-04T21:31:09Z
• Authors: Jonghwi Choi; Changhwan Lim; Hyungdae Kim
• Keywords: Decay heat; Spent fuel pool; Condenser (optics)

Abstract When a station blackout accident occurs in a nuclear power plant, active cooling of spent nuclear fuels stored in a water pool using pumps is not available. As a result, the stagnant water in the pool gradually heats up via decay heat from the spent fuels and evaporates, thus exposing the spent fuels to air. This rapidly overheats the spent fuels and produces hydrogen gas due to oxidation of the zircaloy cladding. Accumulation of hydrogen gas can result in harmful detonation in the spent fuel storage building similar to what occurred in the Fukushima accident. In this study, a new concept of a gravity-assisted heat pipe that removes decay heat of spent fuels in a water pool by natural convection of ambient air is proposed. In the design, the condenser at the top of the heat pipe consists of several finned tubes for passive air cooling while the evaporator at the bottom is a single rod submerged in the spent fuel pool, which is called fork-end heat pipe (FEHP). A theoretical analysis model of a FEHP was developed and a laboratory-scale specimen was manufactured and tested for validation. It was found that the developed theoretical analysis model reasonably predicted the heat transfer rate of the FEHP specimen at diverse operating conditions and the operating limit point where the heat transfer rate is maximized due to the counter-current flow limit phenomenon.