HTGR Knowledge Base

Conference Article: Evaluating on graphite oxidation during an air ingress accident in HTTR

Iyoku, T.; Maruyama, S.; Ishihara, M.; Shiozawa, S. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment); Ohashi, K.; Okamoto, F.; Hayakawa, H. (Fuji Electric Co. Ltd., Tokyo (Japan))

Abstract

The High Temperature Engineering Test Reactor (HTTR) is a graphite-moderated and helium gas-cooled reactor with prismatic fuel elements of hexagonal blocks. Each fuel element consists of graphite sleeves containing fuel compacts and a graphite block holding graphite sleeves. A support post is a cylindrical component and the most essential element to support the core. There are two kinds of accidents classified as an air ingress accident in the safety design of the HTTR. One is the rupture of the primary concentric hot gas duct at the reactor pressure vessel (RPV) inlet nozzle, the other the rupture of a stand pipe attached to the top head closure of the RPV. The graphite structures will be oxidized during the air ingress accidents. It was found from this study that the air ingress accident of the guillotine rupture of the primary concentric hot gas duct was the severest from the graphite oxidation point of view and the oxidized graphite structures maintained the structural integrity after the accident. There is also no possibility of detonation induced by the produced carbon monoxide in the containment vessel.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Technical committee meeting on response of fuel, fuel elements and gas cooled reactor cores under accidental air or water ingress conditions. Beijing (China). 25-27 Oct 1993
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--784, pp:72-78