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Conference Article: Degradations of thermal shock resistance and the fracture toughness of reactor graphite subjected to neutron irradiation

Sato, S.; Kawamata, K.; Kurumada, A.; Ugachi, H. (Ibaraki Univ., Hitachi (Japan). Faculty of Engineering); Awaji, H

Abstract

This paper deals with the irradiation effects on the thermal shock resistance DELTA = sigmat k/Ea (sigmat: tensile strength, k: thermal conductivity, E: Young's modulus, a: thermal expansivity) and the thermal shock fracture toughness nabla = KIc k/Ea (KIc: fracture toughness value of mode 1) in addition to other mechanical properties such as the diametral compressive strength and fracture toughness. Two kinds of near isotropic graphite subjected to neutron irradiations of (1.1 - 1.5) x 1021 n/cm2 (> 29 fJ) at 750 - 1000 deg C are prepared for the measurements. One is an isostatically molded graphite IG-11 with fine grain petroleum coke. The other is a binderless molded graphite HCB-18 which was prepared using mesophase pitch carbon of very fine grain size. These measurements are carried out by means of our developed disk testing method. Results show that both the thermal shock resistance and the thermal shock fracture toughness of the two graphites after irradiation are found to decrease considerably in contrast with increasing trends of the usual mechanical strengths.

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key words: graphite; htgr type reactors; irradiation; neutron beams; physical radiation effects; temperature dependence; thermal expansion; thermal shock; very high temperature; young modulus; carbon; expansion; gas cooled reactors; graphite moderated reactors; mechanical properties; particle beams; radiation effects
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:144-157