HTGR Knowledge Base

Conference Article: Structural assessment of prismatic blocks for pin-in-block fuel element

Takikawa, N.; Koike, H.; Tanaka, M. (Kawasaki Heavy Industries Ltd., Tokyo (Japan)); Arai, T.; Iyoku, T.; Ide, A

Abstract

The reference design of the standard fuel elements for the experimental very high temperature gas-cooled reactor (VHTR) is based on the prismatic pin-in-block type fuel elements using IG-11 graphite material. The variants of VHTR standard PIB fuel elements have been designed mainly from a viewpoint of improving the thermal performance of the VHTR core. The dimensions of these variants are shown. Based on the above variants, the structural assessment was carried out by using the computer programs for two- and three-dimensional finite element methods, and also taking the effect of fast neutron irradiation into account. In this paper, the operating stress, residual shutdown stress and seismic stress at the block joints of a standard PIB type fuel element are reported. Finally, the conclusion of the assessment to be recommended on the current VHTR PIB type fuel elements is discussed. Thermal and irradiation-induced stresses, seismic stress, stress evaluation method, analytical approach to accurately determine the temperature field and stress in specified fuel elements and so on are described. The parameters controlling the thermal stress field are the temperature difference of coolant and the thickness of outer webs. Regarding the irradiation-induced stress, the average temperature of graphite has a significant effect on the irradiation load and dose. Dowel socket joints are preferable in view of seismic load.

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key words: dynamic loads; earthquakes; fuel elements; graphite; htgr type reactors; jackets; neutron beams; physical radiation effects; reactor materials; residual stresses; sleeves; stress analysis; temperature dependence; thermal stresses; beams; carbon; gas cooled reactors; graphite moderated reactors; particle beams; radiation effects; reactor components
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:90-98