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Conference Article: Simulation of the pebble bed modular reactor natural air convection passive heat removal system

Dams, M.L. (Integrators of System Technology Ltd, Waterkloof (South Africa))

Abstract

Cooling of the Pebble Bed Nuclear Reactor under evaluation in South Africa is primarily effected by the flow of helium through the cavity which contains the nuclear fuel. However, apart from this, a certain amount of heat flows from the reactor cavity, through the graphite barrel and reactor vessel to the containment building and ultimately to the environment During normal operation this passive heat loss represents approximately 1MW for a 100MW reactor and constitutes an undesirable loss of power. In the event of a shutdown or loss of main coolant, however, this passive heat removal is relied upon to remove the decay heat from the core. A study was initiated to simulate the process of this heat removal to provide an indication of the maximum vessel temperature and power transfers after shutdown. However, there is a lack of precise data indicating values for thermal conductivity, heat transfer coefficients, heat capacities or even densities. This paper describes the assumptions made and the manner in which these data were estimated so as to provide what is hoped to be a reasonably accurate estimate of the behaviour of the passive heat removal process.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Technical committee meeting on high temperature gas cooled reactor technology development. Johannesburg (South Africa). 13-15 Nov 1996.
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--988, pp:213-227