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Science and Technology of Nuclear Installations
Volume 2014 (2014), Article ID 247862, 9 pages
Research Article

Effect of Flow Blockage on the Coolability during Reflood in a 2 2 Rod Bundle

Korea Atomic Energy Research Institute, Daedeok-daero 989-111, Yuseong-Gu, Daejeon 305-353, Republic of Korea

Received 28 October 2013; Accepted 5 March 2014; Published 1 April 2014

Academic Editor: Junli Gou

Copyright © 2014 Kihwan Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


During the reflood phase of a large-break loss-of-coolant accident (LBLOCA) in a pressurized-water reactor (PWR), the fuel rods can be ballooned or rearranged owing to an increase in the temperature and internal pressure of the fuel rods. In this study, an experimental study was performed to understand the thermal behavior and effect of the ballooned region on the coolability using a 2 × 2 rod bundle test facility. The electrically heated rod bundle was used and the ballooning shape of the rods was simulated by superimposing hollow sleeves, which have a 90% blockage ratio. Forced reflood tests were performed to examine the transient two-phase heat transfer behavior for different reflood rates and rod powers. The droplet behaviors were also investigated by measuring the velocity and size of droplets near the blockage region. The results showed that the heat transfer was enhanced in the downstream of the blockage region, owing to the reduced flow area of the subchannel, intensification of turbulence, and deposition of the droplet.