A. Stern, J.C. Brachet, V. Maillot, L. Portier and A. Pineau • Protocols allowing to obtain homogeneous monophased alpha and « prior beta » samples with different oxygen contents were validated for the two alloys M5 ® and Low-tin Zy4. • Mechanical tests transition in the failure mode for monophased “prior ” samples depending on the test temperature and of the contents of oxygen studied (0.25 ; 0.5 ; 0.7 and 0.9wt%). • Mechanical studies by bending are in progress in order to characterize the alpha phase for the two alloys. • Fractographic studies are in progress in order to analyse more in depth the failure mode. CONTEXT CONTEXT CONCLUSIONS CONCLUSIONS DMN/SRMA Objective and approach : The objective is to model the HT oxidized multilayered material behaviour. The approach consists in elaborating the different homogeneous phases [1] and studying them separatly [2], then integrate all the data [3] to reinterpret the global multilayer material behaviour starting with a as-received sample in form of sheet from industrial alloys from AREVA NP Fuel: Low-tin Zy4 (Zr- 1,3Sn(Fe,Cr,O)) and M5 ® (Zr-1Nb(O)) : Modelisation of the global multilayered material Elaboration of monophased samples with different oxygen contents HT Homogenization in inert atmosphere to obtain monophased samples : [1] Elaboration of multiphased samples: HT oxidation followed by quench, using DEZIROX experimental device (two sides oxidation) : (Low-tin Zy4 : 0.9% wt O) « prior beta » ZrO 2 (O) L t (M5 ® : 0.25% wt O homogenized at 1200°C during 3h) « prior beta » t L [1 ] L. PORTIER, T. BREDEL, J.C. BRACHET, V. MAILLOT, J.P. MARDON, A. LESBROS, “Influence of Long Service Exposures on the Thermal-Mechanical Behavior of Zy-4 and M5™ Alloys in LOCA Conditions”, 14 th Int. ASTM Symp. on “Zr in the Nuclear Industry”, Stockholm, 13-17 June 2004,ASTM-STP [2 ] JC. BRACHET, L. PORTIER, V. MAILLOT, T. FORGERON, JP MARDON, P. JACQUES, A. LESBROS, “Overview of the CEA data on the influence of hydrogen on the metallurgical and thermal-mechanical behavior of Zircaloy-4 and M5™ alloys under LOCA conditions” , proceeding of the NSRC meeting, Oct. 25-27 th , 2004, Washington-DC, USA EXPERIMENTAL APPROACH AND RESULTS OBTAINED DURING THE STUDY EXPERIMENTAL APPROACH AND RESULTS OBTAINED DURING THE STUDY • The zirconium-based cladding tube, acts as the primary barrier for confinement of the radioactive fuel , and its integrity as well as its dimensional stability are key parameters during hypothetical accident scenarii . • During a Loss of Coolant Accident (LOCA), the clad may be subject to a rapid increase of temperature (up to 800-1200°C) in steam environment , which induces accelerated oxidation until quenching during the reflooding of the core . 360°C Coating of zirconia ~ brittle Phase (O) ~ brittle Phase “Prior “ ± ductile T(°C) time quench 1000°C 10% %at. O 66,6 ~30 ~5 à ZrO 2 %at. O 66,6% ~30% ~5 à Clad thickness ZrO 2 (O) Prior Optical micrograp hy of the clad’s thickness (after HT oxidation ) Contrary to oxidation at nominal temperatures (300-360°C): an important fraction of oxygen atoms diffuses in the suboxide metal and tends to promote embrittlement of the clad (after quench). w L t Study of each phase (here « prior beta » phase) Finite elements calculati on ZrO 2 (O) … « prior » [2] [3] Low-tin Zy4 : 0.9% wt O Fontevraud, 18-22 September 200 Fontevraud, 18-22 September 200 Low-tin Zy4 : 0.25% wt O Acknowledgements to AREVA NP Fuel (J.P. Mardon for supplying the alloys) and EDF/SEPTEN (A. Lesbros) <3% « Prior beta » ZrO 2 M5 ® is a registered trade mark of AREVA NP