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Post-irradiation Examination of the lower part of the Phebus FPT2 degraded bundle


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Titre du congrès :ICAPP seventh International Conference on Advances in Nuclear Power Plants Ville du congrès :Nice Date du congrès :13/05/2007

Résumé

The Phébus PF project is an international project examining the release and behaviour of fission products from irradiated fuel. It is lead and is being carried out by the French Institut pour sûreté et radioprotection nucléaire (IRSN) at Cadarache in collaboration with the European Commission and the EU national research institutes as well as the USA, Canada, Korea, Japan & Switzerland. FPT1 examined bundle degradation & release under steam atmosphere while FPT2 was carried out under steam-limited (reducing) conditions. After an initial campaign of macrophotography and examination of the major features of the degraded bundle at ITU, the PIE
continued with the extraction of six selected sites from different levels to perform microscopic examination and analysis of the structures found there. This paper reports on the initial findings in the lower part of the bundle.
The macroscopy confirmed the state of the bundle determined by the immediate post-test tomography carried out at Cadarache. The bundle, as in previous tests, had a characteristic central cavity and a corium pool at one-third height of the bundle, while the upper part showed substantial oxidation, damage and distortion.
The corium pool extended the full width of the bundle and appeared to be deeper than that of FPT1. The corium appears to be fully oxidic and has similar amounts of uranium and zirconium with traces of fission products, structural materials and shroud material Beneath the pool, the cladding was still substantially oxidised and distorted with some fuel-cladding interaction.
There was considerable debris beneath the bundle including zones of corium as well as melted metallic structures that probably originated from cladding and reactor structural materials. The extent of damage indicated that the most extreme temperatures were not achieved at this level.