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Conference Article: Metallic And Graphite Materials For Out-Of-Core and In-Core Components of The VHTR: First Results Of The CEA R&D Program

J.L. Séran, P. Billot, J.P. Bonal, L. Gosmain, CEA/DEN/Saclay, Gif sur Yvette, FRANCE; H. Burlet, R. Couturier, CEA/DRT/Grenoble, Grenoble Cedex, FRANCE; J.C. Robin, CEA/DEN/Cadarache, Saint Paul lez Durance, Cedex, FRANCE; B. Riou, Framatome-ANP/Novatome, Lyon Cedex, FRANCE

Abstract

The behavior of the different structural material represents an important critical issue regarding the feasibility of gas-cooled reactors of VHTR-type. This paper focuses on the qualification studies implemented on metallic and graphite materials that are candidates for out-of-core components and in-core applications. Regarding high temperature metallic materials for primary circuit applications, we describe the main microstructural and mechanical characterizations allowing to assess at 850°C, before and after ageing, the creep, tensile and Charpy behaviors of the alloy Haynes 230 when compared with the alloy 617 considered up to now as the reference material for high temperature metallic components of the HTGR’s. The qualification of materials for discs of gas turbine corresponds to another major critical issue. The results presented here highlight the interest to progress in the HIP + forged way for the Udimet 720 alloy. On the other hand, regarding the in-core components, a large program of out-pile, in-pile and post irradiation characterizations is planned to be implemented at CEA to select and qualify the best graphite grades. This program has started by corrosion studies to analyze, via thermo-gravimetric analysis and using the Oxygraph facility, the graphite behavior in case of air ingress in the primary circuit. The main objective is to reach oxidation kinetics parameters for various available graphites in different conditions and to link graphite oxidation results with the degradation of its mechanical properties. The first results of this program are reported in this paper.

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key words: HTGR, VHTR, Haynes 230, Udimet 720, graphite, mechanical properties, corrosion properties, oxidation, irradiation effects, accidental conditions, air ingress.

Reference:: Proceedings of the Conference on High Temperature Reactors, Beijing, China, September, 22-24, 2004; International Atomic Energy Agency, Vienna (Austria); HTR-2004, pp:1-16