M5_Framatome cladding high temperature oxidation behavior during simulated LOCA transients

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Submitted on 19 Sep 2019

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M5Framatome cladding high temperature oxidation behavior during simulated LOCA transients

Pierre Barberis, Céline Ly, Roland Zino

To cite this version:

Pierre Barberis, Céline Ly, Roland Zino. M5Framatome cladding high temperature oxidation behav-ior during simulated LOCA transients. 19th International Symposium on Zirconium in the Nuclear Industry, May 2019, Manchester, United Kingdom. �hal-02291934�

19th International Symposium on Zirconium in the Nuclear Industry Manchester, UK - May 19-23, 2019

Property of Framatome - © Framatome All rights reserved

P. Barberis, C. Ly Framatome/CRC, Avenue Paul Girod, 73400 Ugine, France R. Zino Framatome, 10 rue Juliette Récamier, 69456 Lyon, France

Presently at École des Mines de Saint-Etienne, 158 Cours Fauriel, 42000 Saint-Etienne, France

M5

cladding high temperature oxidation behavior

during simulated LOCA transients

1.

Context

Demonstrating the acceptable cladding oxidation behavior in LOCA conditions is critical for the fuel vendor and its customers. Key to this is the accurate characterization of the

cladding’s resistance to breakaway oxidation, which can lead to rapid hydrogen pick-up and loss of ductility. Framatome has developed a dedicated facility at its Paimboeuf plant in order to perform one- and two-sided oxidation tests in steam, with a tight monitoring (temperature, steam flow) .

Protective oxide and a low hydrogen pick-up were observed. These tests confirmed the excellent performance of M5_Framatome cladding and the absence of breakaway oxidation in LOCA relevant conditions, as already showed by V. Garat (TopFuel 2016).

3.

Diffusion modeling

Fick’s equations were implemented in

1D-axisymmetry (whole cladding thickness) and coupled with in-house thermodynamic database. Diffusion

coefficient of oxygen was fit to reproduce experimental data at 1000°C.

Oxygen diffusion as a function of time during 1000 °C oxidation.

Diffusion of Nb, Fe, (and Sn) (independently) in the three phases (oxide, α-Zr(O), β-Zr).

4.

Conclusion & Perspectives

➢ M5_Framatome cladding does not show breakaway oxidation in these tests.

➢ Finite element modeling showed that iron is significantly pushed in the β-Zr phase, while Sn profile is almost flat and Nb migrates from oxide and α-Zr(O) towards β-Zr.

Future steps : To include strong coupling between the chemical potential of the various alloying

elements (phase stabilization) and computations of stress and strains in the various phases.

2.

Experiments & results

Two-sided steam oxidation of M5_Framatome claddings for

5000 s at 800 -1050°C in Paimboeuf facility.

Optical microscopy of the samples • Interface undulation and porosity.

During oxide growth, the interface undulation reaches a maximum at 1030°C then decreases, with no sign

of breakaway by 5000 s.

Oxide and α-Zr(O) thicknesses and hydrogen pick-up

after steam oxidation for 5000 s.

M5_Framatome cladding

exhibits low hydrogen uptake for all tested temperatures.

Inner surface Outer surface

Inner surface _{Outer surface}

M5_Framatome 1030°C (x 500) M5_Framatome 1050°C (x 500) M5_Framatome 1000°C (x 1000) M5_Framatome 985°C (x 1000)

Demonstrates that the

approximation of a dilute solid solution should not be assumed

≈

Oxygen chemical potential as a function of Oxygen fraction.