Title: Validation of Severe Accident Codes on the Phebus Fission Product Tests in the Framework of the PHEBEN-2 Project
Authors: DICKINSON S.DE PASCALE C.GIRAULT N.HERRANZ L.DE ROSA D.HENNEGES G.LANGHANS J.HOUSIADAS C.WICHERS V.DEHBI A.PACI S.MARTIN-FUERTES F.TURCU I.IVANOV I.TOTH BelaHORVATH G.MUELLER Klaus
Citation: NUCLEAR TECHNOLOGY vol. 163 no. 2 p. 209-227
Publisher: AMER NUCLEAR SOC
Publication Year: 2008
JRC N°: JRC33677
ISSN: 0029-5450
URI: http://www.new.ans.org/store/j_3982
http://publications.jrc.ec.europa.eu/repository/handle/JRC33677
Type: Articles in periodicals and books
Abstract: Analyses of severe accidents in nuclear power plants by using integral codes are necessary in order to develop accident management strategies that prevent such acci- dents or mitigate their consequences for the environ- ment. The most important requirement for the development of integral codes is to achieve good predictability of a given accident scenario through the understanding and quantification of severe accident phenomena and their underlying physical and chemical processes. In this paper, the progress in modeling the processes related to the radioactive source term, and in particular progress re- lated to the release and transport of fission products in the circuit and containment, is demonstrated by the as- sessment of integral and detailed codes using the exper- imental results of the in-pile Phebus fission product tests (FPTs). It is shown that the integral codes are good in predicting both the hydrogen release and the total re- lease of volatile fission products from the bundle. It is also shown that the commonly used fission prod- uct transport codes overestimate the deposited aerosol mass in the Phebus steam generator. However, by using an improved model for the thermophoretic aerosol par- ticle deposition, it has been possible to reproduce the aerosol mass deposited in the steam generator more ac- curately. The containment analyses carried out with both lumped-parameter and multidimensional computational fluid dynamics codes showed that the measured thermal- hydraulic data are accurately reproduced. The aerosol behavior in the containment estimated from the lumped- parameter codes corresponded satisfactorily to the ex- perimental data. The iodine chemistry codes highlighted the substantial role of silver released from the degraded absorber rod (Ag-In-Cd), as it was observed experimen- tally; however, the temporal dependence of the gaseous iodine concentration in the containment atmosphere was poorly calculated. There are plans to improve the mod- eling in order to reproduce better the fission product release from the bundle, the fission product transport in the primary circuit duct, and the gas phase chemistry in the containment, with particular emphasis on gaseous iodine species. Further plans include the analysis of Phe- bus FPT3, which was the last in the series of Phebus tests, with its boron-carbide control rod.
JRC Directorate:Energy, Transport and Climate

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