Fabrication-related impurity contamination and stress corrosion cracking of austenitic stainless steel core-internal components
- and others
The stress corrosion cracking and microstructural characteristics of boiling-water-reactor neutron absorber tubes, a control blade sheath, and core shroud welds, were investigated by slow-strain-rate tensile testing and advanced metallographic techniques. The results from the absorber tubes and sheath indicate strongly that irradiation-induced grain-boundary Cr depletion and high levels of oxygen and fluorine in the material are important factors that exacerbate susceptibility to irradiation-assisted stress corrosion cracking. The heat-affected zone of the simulated core shroud welds was significantly contaminated by oxygen, fluorine, and molybdenum as a result of exposure to weld fumes. Significant fluorine contamination occurred only in association with oxygen contamination and was higher in the oxygen-rich region beneath the surface weld scale, grain boundaries, and oxides. Similar contamination was also observed in a field-cracked Type 304L core shroud weld. Grain boundaries of the heat affected zone of the shroud weld were characterized by high oxygen, fine oxide particles, and fluorine, but grain-boundary carbides, Cr depletion, or martensite film were absent. These observations and previous reports on the strong influence of weld scale indicate that oxygen and fluorine contamination and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of core shrouds even in the absence of thermal sensitization.
- Research Organization:
- Argonne National Lab., IL (United States)
- Sponsoring Organization:
- Nuclear Regulatory Commission, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 539890
- Report Number(s):
- ANL/ET/CP--94570; CONF-970832--; ON: DE98000645
- Country of Publication:
- United States
- Language:
- English
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