Corrosion of Zirconium Alloys Adrien Couet 1 , Yalong He 1 , Kurt - PowerPoint PPT Presentation

The Effect of Photon Irradiation on the Corrosion of Zirconium Alloys Adrien Couet 1 , Yalong He 1 , Kurt Terrani 2 , Samuel Armson 2 , Michael Preuss 3 , Taeho Kim 1 , Mohamed Elbakhshwan 1 , and Li He 1 1 University of Wisconsin-Madison, Madison, WI USA 2 Oak Ridge National Laboratory, Oak Ridge, TN USA 3 The University of Manchester, Manchester UK 19 th International Symposium on Zirconium in the Nuclear Industry The Midland, Manchester, UK 05.20.2019 – 05.23.2019 UW Envir vironmen menta tal l Degradatio tion of Nuclear clear Mater teria ials ls Lab aborat atory th Inter 19 19 th ternatio tional l Symposiu ium m on Zirco coniu ium m in the e Nuclear clear Industr try

C ONTENT ENTS • Introduction • The effect of UV on corrosion of Zircaloy-4 - Introduction Part I - Experimental - Results: Microstructure characterization with SEM and TEM • The effect of γ -ray on corrosion of Zircaloy-4 - Introduction Part II - Experimental - Results: Microstructure characterization with ASTAR and TEM • Conclusion UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 2 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

I NT NTRODU RODUCTION TION S OURCES OF P HO ES OF HOTONS • Various photon sources in nuclear power plants: - Gamma rays induced by prompt fission and nuclear decays - UV light induced by the decelerating electrons in water (Cerenkov effect) UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 3 th Interna [1] Figures from https://fineartamerica.com 19 19 th ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

I NT NTRODU RODUCTION TION P REVIO EVIOUS R ESU OF UV E FF SULTS TS OF FFECT ECT • Effect of UV on Zr-alloy corrosion: Fig. Example of electrochemistry experiment results with UV irradiation [1] - Open circuit potential of Zr alloy vary by a few tens of mV by the UV irradiation on the sample. - Corrosion characteristic of Zr alloy is changed by UV irradiation and it can be confirmed by In-situ electrochemical impedance spectroscopy. UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 4 th Interna [1] Y-J. Kim et al., J. ASTM Int. 7 (2010) 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

I NT NTRODU RODUCTION TION P REVIO EVIOUS R ESU OF G AM AMMA - RA RAY E FF SULTS TS OF FFEC ECT • Effect of γ -ray on Zr-alloy corrosion: Fig. Summary of the measured oxide thickness and ATR corrosion rate correlates with γ/n flux. - Recent results show that the weight gains from experimental data are significantly larger than the predicted weight gains when the gamma/neutron ratio is larger. - Potential effect of γ -rays on corrosion rate. UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 5 th Interna [1] D. M. Rishel et al., ASTM STP 1597 (2018) 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 6

Part I: The effect of UV on corrosion of Zircaloy-4 M OTIV IVATIO TION • Photo-electrochemical behavior from UV irradiation - When light of a suitable energy hv , is absorbed by the oxide film, electrons can be excited from occupied electric states into unoccupied ones: ℎ𝑤 → 𝑓 − + ℎ + - The other ½ reaction can be with water to produce oxygen 2𝐼 2 𝑃 + 4ℎ + → 𝑃 2 + 4𝐼 + Our goals of this project: ➢ Study the effect of in-situ photon irradiation on fuel cladding corrosion mechanism ➢ Propose a mechanism to explain photon irradiation effect on corrosion rate of zirconium alloy in high temperature water condition UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 7 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 E XPE PERIME RIMENT NTAL AL • Experiment Table. Chemical composition of Zircaloy-4 1) Static autoclave corrosion for 7 d Element Zr Sn Fe Cr Si 2) Flowing loop corrosion for 7 d Composition Bal. 1.27 0.22 0.11 0.01 - Temperature: 260 ℃ (wt.%) Dia. = 2.54 mm Fig. Schematic of the autoclave with sapphire window for in-situ UV irradiation Fig. Schematic of the circulation loop connected with the autoclave UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 8 th Interna 19 19 th ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 E XPE PERIME RIMENT NTAL AL • UV source with energy : 1.9 – 5.0 eV. (250 – 650 nm) Average Cerenkov UV Energy (2.35 eV, 527 nm) ZrO 2 band gap range (1.8 - 5.2 eV, 240 - 680 nm) Fig. UV source output with power density 8.62W/cm 2 UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 9 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 SE SEM M A NAL OF O XIDI ZED S URFACE ALYSIS SIS OF DIZED • Corrosion and exposure to the UV source for 7 days in flowing autoclave UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 10 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 SE SEM M A NAL OF O XIDI ZED S URFACE ALYSIS SIS OF DIZED • Corrosion and exposure to the UV source for 7 days in flowing autoclave • Deposits are present in the UV exposed central region of the sample. • Deposits are distributed on the surface, their distribution is homogeneous. • Deposits are Fe-rich oxides particles • No Fe oxide deposits were observed on the back of the irradiated sample or on the sister sample facing another sapphire window without UV source . UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 11 th Interna 19 19 th ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 SEM SE M A NAL OF O XIDI ZED S URFACE ALYSIS SIS OF DIZED • Corrosion and exposure to the UV source for 7 days in static autoclave UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 12 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 SE SEM M A NAL OF O XIDI ZED S URFACE ALYSIS SIS OF DIZED • Corrosion and exposure to the UV source for 7 days in static autoclave - Particles deposits are oxides rich in Fe and some Al is observed. UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 13 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 TEM EM A NAL OF O XIDIZE DIZED Z IRCAL CALOY -4 ALYSIS SIS OF • Cross-sectional analysis of oxidized Zircaloy-4 with UV irradiation: TEM diffraction analysis of Fe rich oxide particles Element Fe O C Ni Static 38 45 4 5.8 - After corrosion test in static autoclave, the Flowing 39.2 53.9 0.4 3.6 dissolved Fe concentration is below 100 ppb Element Al Mn Mg Zr (below ICP detection limit) Static 4.9 2.7 0.14 -- Table. Average elemental composition (at.%) for particle Flowing 2.9 -- -- -- deposits formed after UV exposure UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 14 th Interna 19 19 th ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part I: The effect of UV on corrosion of Zircaloy-4 M ECHA OF UV UV ON ON Z R O 2 CHANISM NISM OF • Photo-induced electrochemical process at ZrO 2 surface: • Photo-reduction of soluble cations (mostly Fe 2+ ) • Other ½ cell reaction is still under investigation Potential (eV) (2) electron-hole pair (3) Redox reactions generation Fe 2+ + 2e - → Fe - Conduction band 3Fe + 2H 2 O → Fe 3 O 4 + 3H 2 E C (Oxidation of Fe on the ZrO 2 surface) Origin of CRUD? E F E g = 2 – 5 eV (2’) electron -hole pair (4) Hypothesis: Oxide dissolution by holes recombination ZrO 2 + 4h + → Zr 4+ + O 2 E v Valence band - (1) UV irradiation Metal Zr ZrO 2 Water UW Environme onment ntal Degr gradat dation on of Nuclea ear Mater erial als s Laborato oratory 15 th Interna 19 th 19 ernation onal al Sympo posi sium m on Zircon onium m in the Nuclear ear Indust stry ry

Part II: The effect of γ -ray on corrosion of Zircaloy-4 16