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Conference Article: Numerical analysis of the release of metallic fission product in high temperature gas-cooled reactor

Fujii, S.; Tsubosaka, A.; Niguma, Y. (Kawasaki Heavy Industries Ltd. (Japan)); Hirano, M.; Suzuki, K. (Japan Atomic Energy Research Institute (Japan))

Abstract

HTGR core should be designed under the limit of circulating coolant activity and plateout activity in the primary circuit. Release of metallic fission product which is important in plateout activity strongly depends on a geometry of coated particle fuel and on a space distribution and time history of temperature, etc. Therefore, many iterations of a series of nuclear, thermal and fission product release analyses are required for selection of suitable fuel and core dimensions. At the stage of conceptual core design, however, it seems to be impossible to execute these enormous iterative analyses. In this paper, for the purpose of alleviating the troublesome routines, a simplified calculating procedure of Cs137 release, the most important metallic fission product, is presented as the results of the parametric survey analogues to sensitivity analysis. At first, several parameters considered to play a fair role in Cs137 release are selected and are varied independently in sensitivity analysis. Secondly, on the bases of analytic results we pick out the main parameters that have significant effects on Cs137 release. The results show: (I) the characteristics of Cs137 release can be explained by the time-averaged core maximum temperature: T-tildefmax. (II) the dominant release is that from 'intact particles' rather than tailed particles in the range of T-tildefmax>1300 deg. C under the assumption of failure fraction 0.1%. (III) failure fraction up to 2% has no significant effect on Cs137 release at T-tildefmax=1400 deg. C. (IV) Cs137 release decreases to 1/5 when the thickness of SiC layer increases from 25mu to 50mu. (V) in comparison with pin-in-block fuel type, multi hole fuel type is lower in Cs137 release.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Specialists' meeting on fission product release and transport in gas-cooled reactors Berkeley (United Kingdom) 22-25 Oct 1985
International Atomic Energy Agency, International Working Group on Gas-Cooled Reactors, Vienna (Austria)
IWGGCR--13, pp:208-220