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Conference Article: Analysis of core flow deviation caused by the large gaps between horizontal block interfaces

Suzuki Kunihiko; Suzuki Katsuo; Mogi, H.; Fumizawa, M.; Iyoku, T.; Sawa, K. (Department of Power Reactor Projects, Japan Atomic Energy Research Inst., Tokai, Ibaraki)

Abstract

There are various leak flow paths between blocks in the experimental VHTR core. Especially, leak flow in the gap between horizontal surfaces of fuel blocks is called ''crossflow''. Generally, the coolant flows from the fuel channel into the gap between columns. As its results fuel temperature rises. In case of the birth of large gap between horizontal block interfaces, the crossflow caused by it effects significantly on the core flow distribution, core temperature distribution and F.P. release. In this paper, the horizontal core offset between the core upper structure and the core support structure is postulated as the cause of occurrence of large horizontal gap at fuel column. A prediction method of large horizontal gaps between blocks, and analytical method and results of core flow distribution are discussed. Analytical results of core behavior in the core flow deviation caused by the gaps between horizontal block interfaces are also presented. Evaluation of fission product release depending on the flow distribution change is also carried out.

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key words: computerized simulation; coolants; fission product release; fuel channels; gas cooling; gas flow; high temperature; primary coolant circuits; temperature distribution; vhtr reactor; cooling systems; cooling; enriched uranium reactors; experimental reactors; fluid flow; gas cooled reactors; graphite moderated reactors; helium cooled reactors; htgr type reactors; power reactors; reactor channels; reactor components; reactor cooling systems; reactors; research and test reactors; simulation; thermal reactors
Reference:
Specialists' meeting on safety and accident analysis for gas-cooled reactors. Oak Ridge, TN (USA). 13-15 May 1985
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--358, pp:313-323