'The PHEBUS FP integral source term experimental project, with emphasis on iodine selective filtering'

The PHEBUS FP (Fission Product) Project is concerned with LWR severe fuel damage and fission product source term experimentation. Highly irradiated fuel pins are run in accidental conditions until significant UO2 melting occurs. Structural material and fission product aerosols and vapours are swept into a scaled-down primary circuit. A circuit leak is simulated and a reactor containment provided for long term FP behaviour study. The fraction and nature of real radioactive fission product mixtures that reach the containment, and their behaviour in the containment are critical to accident source term estimates and relevant to future filter system designs. Considerable work is performed to measure the behaviour of the different airborne fission products including the identification of the iodine species. Special interest will be devoted to the possibility of the existence of airborne compounds for which the off-gas filter has not been designed today. Iodine chemistry is studied and monitored in the containment using on-line measurements and filters as well as off-line sampling techniques. The selective retention of airborne iodine at elevated temperature and high pressure was preliminarily tested (at KfK Karlruhe) with different sorbents to prove the operational capabilities of iodine species samplers, used as an important means for the analysis of the containment atmosphere. PHEBUS FP is a CEC-JRC and CEA-IPSN co-sponsored project operating in the existing Cadarache based PHEBUS experimental reactor, with the direct participation of Canada, Japan, Korea and the United States