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Title: Bypass flow computations on the LOFA transient in a VHTR

Bypass flow in the prismatic gas-cooled very high temperature reactor (VHTR) is not intentionally designed to occur, but is present in the gaps between graphite blocks. Previous studies of the bypass flow in the core indicated that the cooling provided by flow in the bypass gaps had a significant effect on temperature and flow distributions for normal operating conditions. However, the flow and heat transports in the core are changed significantly after a Loss of Flow Accident (LOFA). This study aims to study the effect and role of the bypass flow after a LOFA in terms of the temperature and flow distributions and for the heat transport out of the core by natural convection of the coolant for a 1/12 symmetric section of the active core which is composed of images and mirror images of two sub-region models. The two sub-region models, 9 x 1/12 and 15 x 1/12 symmetric sectors of the active core, are employed as the CFD flow models using computational grid systems of 70.2 million and 117 million nodes, respectively. It is concluded that the effect of bypass flow is significant for the initial conditions and the beginning of LOFA, but the bypass flow has littlemore » effect after a long period of time in the transient computation of natural circulation.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. National Tsing Hua Univ., Hsinchu (Taiwan). Inst. of Nuclear Engineering and Science
  2. Idaho National Laboratory (INL), Idaho Falls, ID (United States)
  3. City Univ. of Hong Kong, Kowloon (Hong Kong). Dept. of Mechanical and Biomedical Engineering
Publication Date:
OSTI Identifier:
1111047
Report Number(s):
INL/JOU--13-30906
Journal ID: ISSN 1359-4311; TRN: US1400347
DOE Contract Number:
DE-AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Thermal Engineering; Journal Volume: 62; Journal Issue: 2
Publisher:
Elsevier
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
99 GENERAL AND MISCELLANEOUS bypass flow; CFD; VHTR; NATURAL CONVECTION; TRANSIENTS