Study on the effect of Ar⁹⁺ ion irradiation of Zr–2.5 wt.% Nb alloy pressure tube

ABSTRACT

Response of Zr–2.5 wt.% Nb alloy pressure tube, used in PHWR nuclear reactors, to 315 keV Ar⁹⁺ ion irradiation at room temperature was investigated in the fluence range of 3.1 × 10¹⁵–4.17 × 10¹⁶ Ar⁹⁺ cm⁻². Changes in microstructural parameters, viz., the size of coherently scattering domains, microstrain and dislocation density, upon irradiation were ascertained through grazing incidence X-ray diffraction. In general, a decrease in domain size was observed with fluence with a corresponding increase in microstrain and dislocation density. Residual stress measurement showed the development of compressive stresses in place of tensile after irradiation. Transmission electron microscopy showed the formation of dislocation loops of ⟨a⟩-type and ⟨c⟩-type during irradiation. The hardness of irradiated samples, probed through nanoindentation technique, was found to be higher in comparison with unirradiated samples. The above findings have been rationalised on the basis of the defects generated during the Ar⁹⁺ ion irradiation.

KEYWORDS:

• Zr–2.5 wt.% Nb pressure tube
• Ar⁹⁺ heavy ion irradiation
• GI-XRD
• residual stress
• microstructure
• dislocation loops

Acknowledgements

The authors are grateful to Dr. P. Mukherjee and Dr. Gayathri N. Banerjee for their support in carrying out the irradiation experiments at VECC, Kolkata, India. Thanks to Prof. Prita Pant and group for their help in nanoindentation experiments at I.I.T. Bombay, Mumbai, India. The authors are also thankful to Nuclear Fuel Complex, Hyderabad, India for providing the Zr-2.5 wt.% Nb alloy pressure tube used in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.