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Conference Article: Evaluations of the fracture mechanical properties of fuel compacts for the HTTR, with emphasis on thermal shock resistances and neutron irradiation effects

Sato, S.; Kurumada, A.; Kawamata, K. (Ibaraki Univ., Hitachi (Japan). Faculty of Engineering); Suzuki, N.; Kaneko, M. (Nuclear Fuels Industries, Ltd, Tokai (Japan). Tokai Works); Fukuda, K. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment)

Abstract

The High Temperature Engineering Testing Reactor (HTTR), currently under development by Japan Atomic Energy Research Institute (JAERI), uses fuel rods, which contain so called ''fuel compact'' of pellets and a form of fuel made by sintering coated UO2 fuel kernel dispersed in natural graphite matrix in graphite sleeves. The spherical UO2 fuel kernel in the fuel compact is covered with several layers of carbon and SiC. The primary objective of this study was to investigate the mechanical, fracture mechanics properties and the thermal shock resistances of the fuel compact. Disk or rod-shaped fuel compact specimens were prepared by using SiC-kernel coated particles instead of UO2 particles, and by following otherwise the same manufacturing process as that for the real fuel compact. A series of experimental studies were then carried out by using these model specimens. These model specimens were further neutron irradiated in JMTR for fluences up to 1.7x1021n/cm2 (E<29fJ) at high temperature (900 deg. C (+- 50 deg. C)) to study the effects of neutron irradiation on the fracture mechanical properties. In this study, all the fratures were found to occur in the matrix or at the interfaces of kernel particles. No fracture of the SiC-kernel coated particles themselves was found.

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key words: carbon; fracture mechanics; fuel pellets; fuel rods; graphite; httr reactor; matrices; mechanical properties; post-irradiation examination; silicides; thermal shock; uranium dioxide; actinide compounds; chalcogenides; enriched uranium reactors; experimental reactors; fuel elements; gas cooled reactors; graphite moderated reactors; helium cooled reactors; htgr type reactors; silicon compounds; uranium compounds; uranium oxides
Reference:
Specialists' meeting on the status of graphite development for gas cooled reactors. Tokai, Ibaraki (Japan). 9-12 Sep 1991
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--690, pp:70-78