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Conference Article: Design considerations and improvements of the high temperature engineering test reactor (HTTR) for a reactor outlet coolant temperature of 950 deg. C

Sudo, Y.; Saito, S. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan)); Yamada, M. (Fuji Electric Co. Ltd., Tokyo (Japan)); Uno, M. (Kawasaki Heavy Industries, Ltd., Tokyo (Japan)); Ohno, T. (Mitsubishi Atomic Power Industries, Inc., Tokyo (Japan))

Abstract

In 1969, Japan Atomic Energy Research Institute (JAERI) started the development of a very high temperature gas-cooled reactor (VHTR) which could produce the outlet gas of nearly 1000 deg. C for the broad utilization of direct nuclear energy, not only for electric power generation but also for nuclear heat and has been carrying out various researches and developments for the project along with the Japanese industries. In 1987, the Japanese Atomic Energy Commission issued the recommendation on the early construction of HTTR which can produce the outlet gas temperature of 850 deg. C first and 950 deg. C finally, so that the necessary researches and developments may be carried out for establishing and updating the technology basis for advanced HTGRs in future and various innovative basic researches may be conducted as an irradiation test reactor at very high temperature of around 1100 deg. C. This paper presents the design considerations and improvements for achievement of 950 deg. C outlet gas temperature in HTTR along with the design outline of HTTR. The HTTR consists of a 30 MWt core, a primary cooling loop with a helium-helium intermediate heat exchanger and a helium-pressurized water cooler, an auxiliary cooling loop and two reactor vessel cooling systems. The core is composed of 30 fuel columns, 16 control rod columns and 12 replaceable reflector columns, each made by graphite blocks and is cooled by helium gas of 395 deg. C at the inlet of reactor vessel, which flows downward through the core. The maximum fuel temperature with 950 deg. C outlet gas temperature is designed to be about 1500 deg. C in the normal operation and lower than 1600 deg. C during the anticipated abnormal transients. Major design considerations are forwarded to proper blockwise distribution of fuel enrichment, proper flow distribution in the reactor vessel, fuel block design, elimination of hot flow streaks and the design of associated major components in the primary cooling loop.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Technical committee meeting on design requirements, operation and maintenance of gas-cooled reactors. San Diego, CA (USA). 21-23 Sep 1988
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--19, pp:104-112