Volumen II - SAM

element and/or impurities) for the calculation of equilibrium composition to anticipate oxygen profile
evolution in the Zy-4 cladding tube.
a) b)
Fig. 7. Simulation of O diffusion profiles in αZr and βZr at 1200°C: a) α and β phases, b) blow-up of the β
phase region
Diffusion time prediction at 1200°C for ductile-brittle transition in Zy-4
Experiments show that the brittle behaviour of Zr-alloys can be better correlated to the parameters of the
ductile metallic phase (i.e. O-profile in phases, H- hydrides content) [1].
In [1] the ductile-to-brittle temperature transition and the mechanical constitutive laws as a function of the
oxygen content were described. Different experimental tests showed the existence of a ductile-to-brittle
failure mode transition at 20°C for a critical oxygen concentration (around 0.4 wt. %~2.2 at.%).
Simulations at 1200°C were performed in order to predict the diffusion time where the β-prior phase is
completely brittle (and consequently the cladding tube). In Table 4 calculated information for Zy-4 at
1200°C is presented. The thermodynamic and kinetic values used for the simulation are from this work.
For temperatures T16.5 brittle
4. CONCLUSIONS
The coupling of the diffusion code “EKINOX” and the thermodynamics database “ZIRCOBASE was made
via TQ interface.
The simulation of the oxygen diffusion and the phase transformation β→α in a LOCA temperature-time
range was performed.
Diffusion parameters in [1100-1250]°C temperature range were obtained.
Experimental oxygen diffusion information corroborated the diffusion simulations in [1100-1250]°C for
different times.
For Zy-4 steam oxidation at 1200°C the diffusion time for the ductile-brittle transition was predicted.
REFERENCES
1. J.C. Brachet et al., Journal of ASTM International, Vol. 5, No. 5, 2008, Paper ID JAI101116.
2. X. Ma, C. Toffolon-Masclet, T. Guilbert, D. Hamon, J.C. Brachet, J.of Nuclear Mat. 377 (2008) 359–369.
3. N. Bertrand et al., Materials Science Forum, 595-598, 2008, pp 463-472.
4. J. Debuigne, PhD thesis, Paris University (1966), in French.
5. C. Desgranges, PhD Thesis, Université Paris XI Orsay (1998).
6. J.O. Andersson, T. Helander, L.H. Hoglund, P.F. Shi, B. Sundman, CALPHAD 26 (2002) 273.
7. N. Dupin et al. J. Nucl. Mater. 275 (1999) 287.
8. H.M. Chung, T.F. Kassner, J. Nucl. Mater. 84 (1979) 327.
1322