1. DICTRA Mobility Database for Zr alloys C. Toffolon-Masclet, C. Desgranges and J.C. Brachet CEA Saclay, France C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012

2. 2 Context of the study Thermal and Mechanical T, P, interaction fuel/cladding Neutronics formation of irradiation defects (disclocation loops) Properties in nominal operating and accidental conditions Solicitations Physico-chemical Oxidation / hydriding Good mechanical properties and good stability at in-service temperatures and under neutron irradiation Good corrosion resistance Composition of the industrial alloys (wt%) (from AREVA-NP) Zircaloy 4 Zr-1,3% Sn-0,2% Fe-0,1% Cr-(1000-1500ppmO) M5 TM Zr-1%Nb-(150-600)ppmFe -(1000-1500ppmO) PWR assembly In a reactor core : 177 assembly, each one containing 264 cladding tubes  1cm thickness  600  m

3. Why a mobility database for Zr alloys? C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 3 There is a strong influence of the microstructure on nominal operating and accidental conditions Idea : develop a tool able to describe/predict the microstructural evolutions as a function of temperature and time in multi-component industrial alloys upon different scenarios  Thermal treatments during fabrication process  welding operations  In service (T = 300-360°C, corrosion resistance, mechanical properties, irradiation)  In hypothetical accidental conditions (creep properties and high temperature oxydation, residual mechanical behavior)  Long term storage …

4. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 4 Mobility database development Data : o Thermodynamics (Zircobase) o Diffusion experiments (unary, binary, ternary systems) Tracer diffusivity, Intrinsic diffusivity, Interdiffusion coefficients/Marker motion The mobilities M i are described for all binaries, using the following equations : where and

5. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 5 MobiZirc : Mobility database for Zr alloys 10 elements : Cr,Fe,H,Mo,Nb,Ni,O,Sn,V,Zr 9 binary systems : Zr-Nb : HCP_A3, BCC_A2 Zr-Fe : HCP_A3, BCC_A2, FeZr 3, FeZr 2 Zr-O : HCP_A3, BCC_A2, FCC_C1 (ZrO2_cubic),ZrO 2 Mono, ZrO 2 Tetra Zr-H : HCP_A3, BCC_A2, ZrH 2 _Epsilon, FCC_C1 (ZrH 2 Delta) Zr-Sn : HCP_A3, BCC_A2 Zr-Cr : HCP_A3, BCC_A2 Zr-Ni : HCP_A3, BCC_A2 Zr-V : HCP_A3, BCC_A2 Zr-Mo : HCP_A3, BCC_A2

6. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 6 Zr tracor diffusion in BCC_A2 : DICTRA calculations compared to experiments Zr diffusion in  Zr (BCC_A2) Litterature data [99Herzig]:,Chr. Herzig, U. Köhler and S.V. Divinski, J. Applied Physics, 85, 12, (1999), 8119-8130.

7. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 7 O diffusion in  Zr (BCC_A2) Litterature data O tracor diffusion in BCC_A2 [77Perkins] :R. A. Perkins R.A., J. Nucl. Mater., 68, (1977), 148.

8. Zircobase : Thermodynamic database for Zr alloys C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 8 1997-99 : Creation of the 1st Thermodynamic Database for Zirconium Alloys : Zircobase (1) Collaboration between University Paris XI (C. Servant), INPG (H. Ansara, N Dupin, C. Lemaignan) and CEA (C.Toffolon, J.C. Brachet) 1999-2012 : Further developments of the Zircobase 9 elements : Cr,Fe,H,Nb,Ni,O,Sn,V,Zr 20 binary systems : Cr-Fe,Nb,Ni,Zr; Fe-Nb,Ni,Sn,Zr; H-Nb,Ni,O,Sn,Zr ; Nb-O,Sn,Zr; O-Sn,Zr ; Sn-Zr ; V-Zr 7 ternary systems : Cr-Fe-Zr, Cr-Ni-Zr, Fe-Nb-Zr, Fe-Ni-Zr, H-O-Zr, Nb-O-Zr, O-Sn-Zr (1) N. Dupin, I. Ansara, C. Servant, C. Toffolon, C. Lemaignan, J.C. Brachet, Journal of Nuclear Materials, 275, 287-295, (1999).

9. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 9 Application to industrial problematics Study of the precipitation kinetics of  Nb equilibrium phases at 570°C (near industrials thermal Treatments) in a Zr-2.5%Nb alloy(1) Annealing at T = 570°C  Increase of the fraction of  Nb as a function of time TEM micrograph of a Zr-2.5%Nb heat treated at 1045°C and quenched  Zr+  Nb (  Zr,  Nb) Liquide  Nb in  Zr solid solution Zr-Nb binary system

10. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 10 Calculation procedure TEM micrograph of a Zr-2.5%Nb heat treated at 1045°C and quenched Determination of the average width of the laths Half width of a lath  Zr matrix enriched in Nb  Nb precipitation on the inter-laths

11. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 11 Heat Flux (arbitrary unit)  Zr  Zr  Zr +  Zr  Nb  Zr +  H transf  Nb Temperature (°C)  Nb phase fraction determined from the area of the peak characteristic of the retransformation of  Nb upon heating Different annealing time (between 2h and 500h) applied at 570°C Calorimetry after each annealing time. This technic is sensitive to the  Nb phase fraction precipitated

12. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 12  DICTRA calculations  From calorimetry Good agreement : Dictra+Zircomob calculations / experimental kinetics At. % of  Nb phases Variation of the  Nb phase fraction as a function of annealing time

13. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 13 ZrO 2 α Zr Oxygen diffusion profile ZrO 2 β Zr Oxygen diffusion profile < 0 ZrO 2 β Zr α(O) Zr Oxygen diffusion profile x > 0 T ≈ 360°C T ≈ 1200°C β Zr α(O) Zr Oxygen diffusion profile β Zr α(O) Zr Oxygen diffusion profile β Zr Oxygen diffusion profile J ox – J α < 0 < 0 Dissolution of an inner pre-oxide during high temperature transient.

14. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 14 Optical micrographs obtained after oxidation at 1200°C Zircaloy-4 samples with initial inner pre-oxide layer. « Influence of Pre-Transient Oxide on LOCA High Temperature Steam Oxidation and Post-Quench Mechanical Properties of Zircaloy-4 and M5 TM cladding » M. Le Saux et al., 2011 Water Reactor Fuel Performance Meeting, Chengdu, China, Sept. 11-14, 2011 Dissolution of an inner pre-oxide during high temperature transient. After 55s at 1200°C After 187s at 1200°C

15. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 15 Variation of Oxide and αZr thickness as a function of time

16. C. Toffolon-Masclet et al., CALPHAD XLI, Berkeley, USA, June 3-8 2012 16 Outlook Creation of a mobility database for Zr alloys : 10 elements 9 binary systems Typical microstructural evolutions occuring in normal or accidental conditions well reproduced Further work Find a way to take into account Molar Volumes in DICTRA : limitations for oxydation simulations Perform experimental determinations of diffusion coefficient in order to improve the database