Community Research and Development Information Service - CORDIS


The PHEBUS F.P. program is an international effort to investigate, through a series of in-pile integral experiments, the LWR severe accident phenomena; in particular, bundle degradation and the subsequent release and transport of radioactive materials to their containment facilities. Two tests simulating a low-pressure cold leg break under a steam-rich environment have already been successfully performed: FPT-0, with trace irradiated fuel and FPT-1 with re-irradiated BR3 fuel. Both tests have provided experimental data of high interest, particularly concerning iodine release from the fuel bundle, transport in the reactor coolant system and behaviour in the containment.

The analysis of FPT-l, currently in progress, shows that the results exhibit common features and differences with the previous test FPT-0. In both tests, the highest gaseous iodine fractions are obtained after Zicaloy-oxidation phases. The amount measured in FPT-l referred to the initial bundle inventory, is however, significantly lower than in FPT-0. The fast deposition of iodine in the sump as insoluble silver iodine (AgI) observed in FPT-0, appears to be considerably slowed down in FPT-1; to a point that iodine re-volatilisation from the sump, which was inhibited in FPT-0, becomes possible in FPT-1. The results of both tests indicate that the gaseous iodine in the long term is produced by release of organic iodides from the painted condenser surfaces.

The data obtained from the PHEBUS tests indicate that the current modelling in iodine chemistry codes is not fully adequate to model the observed phenomena. The comparison of modelling and experimental data has identified areas of necessary developments: modelling of thermodynamics and kinetics of chemical reactions in the reactor coolant system, of kinetics of organic iodides formation/decomposition and of Ag/I interactions in the containment. The later requires a more accurate knowledge of the Ag physical and chemical state in the containment

Additional information

Authors: JACUEMAIN ET AL, IPSN/DRS, C.E. Cadarache (FR);DICKINSON S, AEA Technology (UK);WREN C, AECL Whiteshell Labatories (CA);POWERS D, Sandia National Laboratories, Albuquerqeu (US);KRAUSMANN E, JRC/ISIS, Ispra (IT);FUNKE F, Siemens (DE);CRIPPS R, Paul Scherrer Institute (CH);HERRERO B, CIEMAT (ES)
Bibliographic Reference: Article: OECD Workshop on Iodine Aspects of Severe Accident Management, pp. 57-78
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top