Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Plant-scale experiments of an air inflow accident under sub-atmospheric pressure by pipe break in an open-pool type research reactor

  • Donkoan Hwang (Division of Advanced Nuclear Engineering, POSTECH) ;
  • Nakjun Choi (Division of Advanced Nuclear Engineering, POSTECH) ;
  • WooHyun Jung (Department of Mechanical Engineering, POSTECH) ;
  • Taeil Kim (Department of Mechanical Engineering, POSTECH) ;
  • Yohan Lee (Division of Advanced Nuclear Engineering, POSTECH) ;
  • HangJin Jo (Division of Advanced Nuclear Engineering, POSTECH)
  • Received : 2022.09.20
  • Accepted : 2023.01.25
  • Published : 2023.05.25
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Abstract

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

Keywords

Acknowledgement

This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science and ICT). (2020R1A4A3079853).

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