Effect of Hydrogen on ZIRLO and Zr-1.0Nb Irradiation Creep ... · – Hydrogen has no effect on the axial irradiation creep of either SRA ZIRLO cladding or Zr-1.0Nb. – The total
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John P. Foster, Guirong Pan, Lu Cai and Andrew Atwood Westinghouse Electric Company
Effect of Hydrogen on ZIRLO® and Zr-1.0Nb Irradiation Creep and Irradiation Growth
ZIRLO® is a trademark or registered trademark of Westinghouse Electric Company LLC in the United States and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.
Introduction • Hydrogen effect on irradiation growth and creep is receiving
considerable attention • Out-reactor results show significant decrease in creep due
to hydrogen • Systematic evaluation of hydrogen effect on irradiation
creep is very limited. • A comprehensive evaluation will be presented, including
different alloy chemistry and microstructure: SRA (Stress Relief Annealed) ZIRLO and (Re-crystallized) RXA Zr-1.0Nb; and in both axial and diametric directions, as well as various burnup levels
20 diameter measurements at each of 7 axial positions. Each axial position spaced 0.5" (12.7 mm)* apart (3 on each side of the capsule C/L) centre line)
32.58 mm*
1 23 4
5 6 7
Permanent standard bolted to capsule jig
• Each measured data point (diameter or length) is the averaged value of numerous repeated measurements at various locations.
• A standard is used to account for experimental setup variation
• The final value of the measurement was also adjusted for standard, temperature variations, and oxide thickness.
Experimental - Data Analysis • The data will be presented as the strain versus the pressure
difference across the sample wall.
• The strain will be evaluated in the axial and the diametric directions o Axial Direction: The total axial strain, or split into axial irradiation growth
and axial irradiation creep components according to, ∆L/Lo(total) = ∆L/Lo(irradiation creep) + ∆L/Lo(irradiation growth)
o Diameter Direction: The total diametrical strain, or split into diametric irradiation growth and diametric irradiation creep components according to, ΔD/Do = ΔD/Do(irradiation growth) + ΔD/Do(irradiation creep)
Conclusions • Another key takeaway: The difference of hydrogen effect on
irradiation growth between SRA ZIRLO (increase) and RXA Zr-1.0Nb (decrease) could be due to alloy chemistry or microstructure. Since SRA ZIRLO and RXA Zr-4 has the same behavior, the amount of alloy elements could be the reason.
Conclusions • The key conclusion: The decrease in in-reactor creep (in
both axial and diametric direction) due to hydrogen is minimal, in contrary, hydrogen significantly decreases the out-reactor creep strain and strain rate
o The proposed mechanism: The irradiation-induced point defects could have diminished the dislocation inhibition effect of hydrides and hydrogen in the solid solution.
Conclusions • Another key takeaway: The difference of hydrogen effect on
irradiation growth between SRA ZIRLO (increase) and RXA Zr-1.0Nb (decrease) could be due to alloy chemistry or microstructure. Since SRA ZIRLO and RXA Zr-4 has the same behavior, the amount of alloy elements could be the reason.
Acknowledgements • The coolant temperature analysis and sample temperature calculations
were performed by John Killimayer and David Rumschlag/Westinghouse.
• Westinghouse is grateful to Southern Nuclear Operating Company for enabling irradiation of the test samples.
• The contributions of Richard Loftin, Ken Turnage and the Vogtle site staff are greatly appreciated.
• The sample diameter, length and oxide thickness measurements were performed by Frank Butcher and Allan MacCormack/AECL. The authors appreciate the assistance of Nick Christodoulou /CNSC (retired) for technical assistance during all aspects of the program including design review, experimental measurement methods, evaluation and interpretation of the data while at AECL and for reviewing the manuscript.