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Title: Numerical study of air ingress transition to natural circulation in a high temperature helium loop

Journal Article · · Annals of Nuclear Energy (Oxford)
 [1];  [1]; ORCiD logo [2];  [1]
  1. Kansas State Univ., Manhattan, KS (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
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Here, the generation-IV high temperature gas cooled reactors (HTGRs) are designed with many passive safety features, one of which is the ability to passively remove heat under a loss of coolant accident (LOCA). However, several common reactor designs do not prevent against a large break in the coolant system and may therefore experience a depressurized LOCA. This would lead to air entering into the reactor system via several potential modes of ingress: diffusion, gravity currents, and natural circulation. At the onset of a LOCA, the initial rate of air ingress is expected to be very slow because it is governed by molecular diffusion. However, after several hours, natural circulation would commence, thus, bringing the air into the reactor system at a much higher rate. As a consequence, air ingress would cause the high temperature graphite matrix to oxidize, leading to its thermal degradation and decreased passive heat (decay) removal capability. Therefore, it is essential to understand the transition of air ingress from molecular diffusion to natural circulation in an HTGR system. This paper presents results from a computational fluid dynamics (CFD) model to study the air ingress transition behavior. These results are validated against an h-shaped high temperature helium loop experiment. Details are provided to quantitatively predict the transition time from molecular diffusion to natural circulation.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
AC05-00OR22725; NE0008412
OSTI ID:
1437917
Alternate ID(s):
OSTI ID: 1549305
Journal Information:
Annals of Nuclear Energy (Oxford), Vol. 111, Issue C; ISSN 0306-4549
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

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Related Subjects

42 ENGINEERING
HTGRs
Air ingress
Diffusion
Natural circulation