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Conference Article: Creep and fatigue crack growth in tubes of HTR components

Roedig, M.; Pfaffelhuber, M.; Schubert, F.; Nickel, H. (Kernforschungsanlage Juelich GmbH (Germany, F.R.). Inst. fuer Reaktorwerkstoffe); Bodmann, E. (Hochtemperatur-Reaktorbau GmbH, Mannheim (Germany, F.R.))

Abstract

As part of the German Projects PNP and HTR 500, experiments on the transferability of fracture mechanics data have been performed. The aim was to work out laws, which are able to describe creep and fatigue crack growth in components at high temperatures. In the creep crack growth experiments, steam reformer tubes of 120 mm o.d. and 10 mm w.th. were provided with an external 360 deg.- crack in circumferential direction. The loading condition was axial tension with superimposed internal pressure. The temperature was 800 deg. C. As a result of the experiments it was found, that creep crack growth in standard specimens as well as in tubes can be described by means of the loading parameter C*. The fatigue crack growth experiments have been performed with a thick walled tube of 197 mm o.d. and 23.5 mm w.th. at 550 deg. C. The tube has been provided with an external 180 deg.- crack in circumferential direction. It was loaded at a frequency of 5 Hz in four point bending. After the first evaluation of results, the comparison of the da/dN vs. DELTA KI curves for standard specimens and tubes show a poor agreement. The reason is thought to be in too conservative assumptions in the calculation of the KI-values.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
High temperature metallic materials for gas-cooled reactors. Proceedings of a specialists meeting held in Cracow, 20-23 June 1988
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--18, pp:131-144