Stress assisted oxide cracking of Zr-2.5Nb pressure tube material
The crack growth rates of un-irradiated and un-hydrided Zr-2.5Nb pressure tube material has been investigated in both air and in vacuum. Pre-cracked CCT samples made from pressure tube were tested in air atmosphere at 300 °C and 350 °C at different stress intensity factors. It was observed that till...
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| Published in: | Journal of nuclear materials Vol. 536; p. 152187 |
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| Main Authors: | , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Amsterdam
Elsevier B.V
01-08-2020
Elsevier BV |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | The crack growth rates of un-irradiated and un-hydrided Zr-2.5Nb pressure tube material has been investigated in both air and in vacuum. Pre-cracked CCT samples made from pressure tube were tested in air atmosphere at 300 °C and 350 °C at different stress intensity factors. It was observed that till a particular stress intensity factor there is no crack growth and after which the crack growth rate increases with increase in stress intensity factor. For the test carried out in vacuum, it was observed that the crack growth rates for air is an order of magnitude higher than that of the crack growth obtained in the vacuum ambience.
A sub-critical crack growth mechanism manifested for unhydrided unirradiated Zr-2.5Nb pressure tube material under static loading has been investigated in both air and in vacuum at 350 °C at different stress intensity factors. This crack growth phenomenon was characterised in terms of stress intensity factor and velocity of crack growth at 350 °C and was found to be associated with a threshold stress intensity factor greater than 22 MPa m1/2 and velocity of crack growth increased with applied stress intensity factor. The stress assisted oxide cracking is less likely mechanism for propagation of flaws in un-hydrided and un-irradiated Zr-2.5Nb pressure tubes as the conditions of high temperature and high stress intensity factor are unlikely to be met for the pressure tubes under the operating conditions of the pressurized heavy water reactors. Figure: Stress assisted oxide Cracking rates (VSAOC) vs Stress intensity factor (KI) at 350 °C. [Display omitted]
•Stress assisted oxide cracking has been demonstrated for unhydrided unirradiated Zr-2.5Nb pressure tube material under static loading.•The velocity of crack growth at 350 °C was determined as a function of stress intensity factor.•SAOC was found to be associated with threshold stress intensity factor of ∼22 MPa m1/2.•The velocity of crack growth increased with increase in applied stress intensity factor.•The SAOC is less likely event for propagation of initial flaws in PTs under operating condition of the PHWRs. |
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| ISSN: | 0022-3115 1873-4820 |
| DOI: | 10.1016/j.jnucmat.2020.152187 |