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Conference Article: Seismic response of HTTR core bottom structures

yoku, T.; Inagaki, Y.; Nishiguchi, I. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of HTTR Project); Futakawa, M. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of High Temperature Engineering); Miki, T.; Jinza, K.; Tomizuka, T. (Fuji Electric Company Ltd, Kawasaki (Japan). Engineering Dept.)

Abstract

The HTTR (High-Temperature Engineering Test Reactor) is a 30 MWt helium gas-cooled reactor, the design of which is underway to achieve first criticality in FY 1995. Core bottom structures of the HTTR, which support the reactor core, consists of keyed plenum blocks, core support posts and others. The keyed plenum blocks located under the core region are large hexagonal blocks combined each other by key/keyway systems. The core support posts are placed below the blocks, allowing relative displacement between the blocks and lower structures by inclination of the posts during an earthquake. Since the key/keyway of the keyed plenum blocks and core support posts are critically important to avoid core degradation at an earthquake, two mock-up tests were conducted under simulated seismic conditions. In the first test, 1/5-scale keyed plenum blocks array was modeled to obtain fundamental characteristics of strain response produced by collisions of the keyed plenum blocks. In the second test, 1/3-scale core bottom structures including the keyed plenum blocks and core support posts were modeled to quantify vertical loads imposed on the core support post and demonstrated structural integrity of the core bottom structures of the HTTR. This paper describes main test results and discusses analytical models to evaluate the structural integrity of the core bottom structures. Major results obtained from the present study are as follows: 1) Structural integrity of the core bottom structures was confirmed and analytical model was developed to predict stresses imposed on the keyways and core support posts. 2) Maximum strains of the keyways were related quantitatively with impact accelerations on the keyed plenum block. 3) Maximum load on the core support post W was found to be expressed as W=Ccentre dotWo, C and Wo denoted constant determined by Wo and dead load on the core support post, respectively.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Seismic behaviour of gas cooled reactor components. Proceedings of a specialists' meeting held in Gif-sur-Yvette, France, 14-16 November 1989
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--22, pp:95-104