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Conference Article: Principles of decay heat removal in reactor technology - Present status and future prospects

Abstract

Reliable and safe decay heat removal is one of the main safety requirements in nuclear reactor technology. Today in all plants worldwide this requirement is fulfilled by active decay heat removal systems. If these systems fail, core melt-down accidents can occur and large amounts of fission products can escape to the environment. New developments worldwide are especially discussed toward the question of how to improve reliability in decay heat removal. In this paper some new proposals are described, and the specific safety questions connected with decay heat removal are discussed. It is shown that a concept of self-acting decay heat removal which avoids core melt-down accidents and which guarantees the retention of the fission products inside the fuel elements even if all active decay heat removal systems fail, can indeed be realized. Some technical details of this principle, which has already been realized for high-temperature reactors, are described in this paper. The differences between active, passive and self-acting concepts are explained. Furthermore, some limitations of the concept of self-acting decay heat removal are shown. In addition to the concept of thermal stability of the core guaranteed by the self-acting decay heat removal, there are requirements of neutron physical, chemical and mechanical stability of the core in all accidents. Future work to prove the required principle is discussed at the end of the paper.

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Reference:

Specialists meeting on decay heat removal and heat transfer under normal and accident conditions in gas cooled reactors. Juelich (Germany). 6-8 Jul 1992

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--757, pp:15-29