PWR Hot Leg Natural Circulation Modeling with MELCOR Code

  • Park, Jae-Hong (Korea Institute of Nuclear Safety) ;
  • Lee, Jong-In (Korea Institute of Nuclear Safety) ;
  • Randall. K. Cole (Sandia National Laboratories, Albuquerque) ;
  • Randall. O. Gauntt (Sandia National Laboratories, Albuquerque)
  • 발행 : 1997.10.01

초록

Previous MELCOR and SCDAP/RELAP5 nodalizations for simulating the counter-current, natural circulation behavior of vapor flow within the RCS hot legs and SG U-tubes when core damage progress can not be applied to the steady state and water-filled conditions during the initial period of accident progression because of the artificially high loss coefficients in the hot legs and SG U-tubes which were chosen from results of COMMIX calculation and the Westinghouse natural circulation experiments in a 1/7-scale facility for simulating steam natural circulation behavior in the vessel and in the hot leg and SG during the TMLB' scenrio. The objective of this study is to develop a natural circulation modeling which can be used both for the liquid flow condition at steady state and for the vapor flow condition at the later period of in-vessel core damage. For this, the drag forces resulting from the momentum exchange effects between the two vapor streams in the hot leg was modeled as a pressure drop by pump model. This hot leg natural circulation modeling of MELCOR was able to reproduce similar mass flow rates with those predicted by previous models.

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