Calculations to Benchmark Probabilistic Fracture Mechanics Computer Codes
This paper describes calculations to estimate component failure frequencies for components using the PRO-LOCA and PRAISE probabilistic fracture mechanics (PFM) computer codes. These calculations focused on the failure mechanism of intergranular stress corrosion cracking for operating conditions that were known to have failed field components. The objective was to benchmark the newly developed PRO-LOCA code against the older PRAISE code that had a much longer history of prior applications. Another objective was to determine the extent to which uncertainties and modeling assumptions may impact calculated probabilities. It was established that advanced modeling capabilities in the PRO-LOCA code simulated parameters that were treated deterministically by the PRAISE code. Excellent agreement of numerical results from the two codes was established once the PRO-LOCA code was applied using selective deterministic treatments. Benchmarking efforts described in a related paper have compared calculated frequencies with those estimated from plant operating experience. Sensitivity calculations have also been performed to address uncertainties associated with residual stresses and applied stresses and temperatures. The capabilities and limitations of the two PFM codes are described along with prior PFM applications to piping integrity issues. Model assumptions are described along with the uncertain nature of inputs and their impacts on calculated probabilities. Also described are calculations with the PRAISE code that have used an alternative crack initiation model based on laboratory data for crack initiation by PWSCC in Alloy-182. Sensitivity calculations with this model address the effects of uncertainties in levels of operating and residual stresses, uncertainties in plant operating conditions, and circumferential variations of stress.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 928285
- Report Number(s):
- PNNL-SA-54226; 401001060; TRN: US200815%%734
- Resource Relation:
- Conference: Proceedings of PVP2007: 2007 ASME Pressure Vessels and Piping Division Conference July 22-26, 2007, San Antonio, Texas USA, 6:51-58
- Country of Publication:
- United States
- Language:
- English
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