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Conference Article: Fatigue behavior of fine-grained isotropic graphite for HTGRs

Ishiyama, S.; Eto, M.; Oku, T. (Japan Atomic Energy Research Inst., Tokai, Ibaraki. Tokai Research Establishment)

Abstract

The principal purpose of this study is to examine the effect of stress ratio, volume, temperature, irradiation and oxidationon fatigue strength of nuclear graphite. Results were summarized as follows. 1) The fatigue tests were performed at stress ratio of 0.5, 0.0, -1.0, -3.5, +infinity, 1/0.3 and 1/0.7 at room temperature and in air. Fatigue data were analyzed statistically and summarized in a modified Googman fatigue diagram. 2) Fatigue tests were performed with many different sizes of specimens and no pronounced difference of fatigue strength was found. 3) The tests were performed at 980 deg C in a vacuum. It was shown that fatigue strength increased about 1.05 times of that at room temperature. 4) Irradiations were performed at temperatures of 575 approx 650 deg C to a influence of 1.92 x 1020 approx 3.20 x 1020 n/cm2. It was shown that the fatigue strength increased to the value 1.2 times of the unirradiation. 5) Oxidation was performed at 500 deg C in air. It was shown that fatigue strength after oxidation decreased as oxidation proceeded.

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key words: fatigue; graphite; high temperature; htgr type reactors; isotropy; oxidation; physical radiation effects; reactor cores; thermal stresses; very high temperature; carbon; chemical reactions; elements; gas cooled reactors; graphite moderated reactors; mechanical properties; radiation effects; reactor components; stresses
Reference:
Specialists' meeting on graphite component structural design, JAERI Tokai (Japan), September 8-11, 1986
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--11, pp:222-226