Modeling of Stress Corrosion Cracking for High Level Radioactive-Waste Packages
A stress corrosion cracking (SCC) model has been adapted for performance prediction of high level radioactive-waste packages to be emplaced in the proposed Yucca Mountain radioactive-waste repository. SCC is one form of environmentally assisted cracking due to three factors, which must be present simultaneously: metallurgical susceptibility, critical environment, and static (or sustained) tensile stresses. For waste packages of the proposed Yucca Mountain repository, the outer barrier material is Alloy 22, a highly corrosion resistant alloy, the environment is represented by the water film present on the surface of the waste package from dripping or deliquescence of soluble salts present in any surface deposits, and the stress is principally the weld induced residual stress. SCC has historically been separated into ''initiation'' and ''propagation'' phases. Initiation of SCC will not occur on a smooth surface if the surface stress is below a threshold value defined as the threshold stress. Cracks can also initiate at and propagate from flaws (or defects) resulting from manufacturing processes (such as welding). To account for crack propagation, the slip dissolution/film rupture (SDFR) model is adopted to provide mathematical formulas for prediction of the crack growth rate. Once the crack growth rate at an initiated SCC is determined, the time to through-wall penetration for the waste package can be calculated. The SDFR model relates the advance (or propagation) of cracks, subsequent to the crack initiation from bare metal surface, to the metal oxidation transients that occur when the protective film at the crack tip is continually ruptured and repassivated. A crack, however, may reach the ''arrest'' state before it enters the ''propagation'' phase. There exists a threshold stress intensity factor, which provides a criterion for determining if an initiated crack or pre-existing manufacturing flaw will reach the ''arrest'' state. This paper presents the research results that quantify the threshold stress, threshold stress intensity factor, and the parameters in the crack growth rate equation based on experimental results developed specifically for Alloy 22 in environments relevant to high level radioactive-waste packages of the proposed Yucca Mountain radioactive-waste repository.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15007748
- Report Number(s):
- UCRL-JC-153349; TRN: US0402469
- Resource Relation:
- Journal Volume: 2003; Conference: ASME Pressure Vessels & Piping Conference, Cleveland, OH (US), 07/20/2003--07/24/2003; Other Information: PBD: 20 Jun 2003
- Country of Publication:
- United States
- Language:
- English
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Validation of Stress Corrosion Cracking Model for High Level Radioactive-Waste Packages
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Related Subjects
36 MATERIALS SCIENCE
ALLOYS
CORROSION RESISTANT ALLOYS
CRACK PROPAGATION
MANUFACTURING
OXIDATION
PRESSURE VESSELS
RUPTURES
SIMULATION
STRESS CORROSION
STRESS INTENSITY FACTORS
STRESSES
TRANSIENTS
WASTES
WELDING
YUCCA MOUNTAIN