Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
권호 표지

Mechanism of Environmentally-Induced Stress Corrosion Cracking of Zr-Alloys

  • Park, Sang Yoon (Advanced Core Materials Lab. Korea Atomic Energy Research Institute) ;
  • Kim, Jun Hwan (Advanced Core Materials Lab. Korea Atomic Energy Research Institute) ;
  • Choi, Byung Kwon (Advanced Core Materials Lab. Korea Atomic Energy Research Institute) ;
  • Jeong, Yong Hwan (Advanced Core Materials Lab. Korea Atomic Energy Research Institute)
  • Published : 2007.08.01
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Abstract

Iodine-induced stress corrosion cracking (ISCC) properties and the associated ISCC process of Zircaloy-4 and an Nb-containing advanced nuclear fuel cladding were evaluated. An internal pressurization test with a pre-cracked specimen was performed with a stress-relieved (SR) or recrystallized (RX) microstructure at $350^{\circ}C$, in an iodine environment. The results showed that the $K_{ISCC}$ of the SR and RX Zircaloy-4 claddings were 3.3 and 4.8MPa\;m^{0.5}, respectively. And the crack propagation rate of the RX Zircaloy-4 was 10 times lower than that of the SR one. The chemical effect of iodine on the crack propagation rate was very high, which was increased $10^4$ times by iodine addition. Main factor affecting on the micro-crack nucleation was a pitting formation and its agglomeration along the grain boundary. However, this pitting formation on the grain-boundary was suppressed in the case of an Nb addition, which resulted in an increase of the ISCC resistance when compared to Zircaloy-4. Crack initiation and propagation mechanisms of fuel claddings were proposed by a grain boundary pitting model and a pitting assisted slip cleavage model and they showed reasonable results.

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