Effect of input distributions on the probabilistic fracture mechanics analysis of reactor pressure vessels
This paper describes current work whose objective is to improve the stochastic models of variables which affect the fracture mechanics analysis of reactor pressure vessels. The effects of two of the more important variables, the shift in reference temperature for nil ductility transition (..delta..RT/sub NDT/) and flaw size, on the probability of vessel failure during a pressurized thermal shock (PTS) incident are studied. Uncertainties in the copper content of weld material have the greatest effect on the variability of simulated values of shift in RT/sub NDT/. The effects of nickel content and fluence are lesser, but significant. These results are inherent in the structural form of the equation used to predict shift. The simulated probabilities of vessel failure are found to vary widely for some of the more popular flaw-depth distributions. Small differences in the way flaw depths are rounded in order to make them compatible with existing simulation codes have profound effects on results. Data on measured flaw lengths are also considered. When length-corrected stress intensity factors are computed for finite-length flaws, simulated failure probabilities decrease. The effect is great enough to justify introducing flaw-length distributions and length-corrected intensity factors into PTS simulation models.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 6473731
- Report Number(s):
- PNL-SA-12038; CONF-840647-30; ON: DE85000832
- Country of Publication:
- United States
- Language:
- English
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CONTAINERS
DEFECTS
DUCTILE-BRITTLE TRANSITIONS
FAILURES
FRACTURE MECHANICS
MECHANICS
PRESSURE VESSELS
PROBABILITY
STRESS INTENSITY FACTORS
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