Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Numerical study on thermal-hydraulics of external reactor vessel cooling in high-power reactor using MARS-KS1.5 code: CFD-aided estimation of natural circulation flow rate

  • Song, Min Seop (Department of Nuclear Engineering, Seoul National University) ;
  • Park, Il Woong (Institute for Nuclear Science and Technology, Jeju National University) ;
  • Kim, Eung Soo (Department of Nuclear Engineering, Seoul National University) ;
  • Lee, Yeon-Gun (Department of Nuclear and Energy Engineering, Jeju National University)
  • Received : 2021.04.27
  • Accepted : 2021.07.21
  • Published : 2022.01.25
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Abstract

This paper presents a numerical investigation of two-phase natural circulation flows established when external reactor vessel cooling is applied to a severe accident of the APR1400 reactor for the in-vessel retention of the core melt. The coolability limit due to external reactor vessel cooling is associated with the natural circulation flow rate around the lower head of the reactor vessel. For an elaborate prediction of the natural circulation flow rate using a thermal-hydraulic system code, MARS-KS1.5, a three-dimensional computational fluid dynamics (CFD) simulation is conducted to estimate the flow rate and pressure distribution of a liquid-state coolant at the brink of significant void generation. The CFD calculation results are used to determine the loss coefficient at major flow junctions, where substantial pressure losses are expected, in the nodalization scheme of the MARS-KS code such that the single-phase flow rate is the same as that predicted via CFD simulations. Subsequently, the MARS-KS analysis is performed for the two-phase natural circulation regime, and the transient behavior of the main thermal-hydraulic variables is investigated.

Keywords

Acknowledgement

This work was supported by the Nuclear Safety Research Program through the Korea Foundation Of Nuclear Safety (KoFONS) using the financial resource granted by the Nuclear Safety and Security Commission (NSSC) of the Republic of Korea. (No. 1903003)

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