ML19134A260
| ML19134A260 | |
| Person / Time | |
|---|---|
| Issue date: | 05/20/2019 |
| From: | Matthew Homiack NRC/RES/DE/CIB |
| To: | |
| Shared Package | |
| ML19136A264 | List:
|
| References | |
| Download: ML19134A260 (5) | |
Text
Extremely Low Probability of Rupture (xLPR)
Matthew Homiack Materials Engineer RES/DE/CIB
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Background===
Purpose:
Determine whether the deterministic approach for evaluating leak-before-break, as outlined in the Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants:
LWR Edition (NUREG-0800), Section 3.6.3, continues to ensure that the probability of piping system rupture is extremely low when considering the presence of primary water stress-corrosion cracking (PWSCC).
Collaborative effort between NRC/RES and the Electric Power Research Institute, Inc.
(EPRI) culminating in xLPR Versions 1 and 2
xLPR Version 2 Key Developmental Documentation
- Supports NRR review
- Completed xLPR Version 2 Code
- User Manual
- User Training
- External Review Board Reports
- Primary Water Stress-Corrosion Cracking Initiation Model Parameter Development, Con"rmatory Analyses, and Validaon
- Veri"caon and Validaon Tesng Results
- Sources and Treatment of Uncertainty
- Summary NUREG
Maintenance and Distribution
- NRC/RES and EPRI completed Addendum to their Memorandum of Understanding on Cooperative Nuclear Safety Research to provide for code maintenance, support, and distribution
- Maintenance
- Conduct under rigorous quality assurance program as in code development
- Distribution
- Domestic: Finalizing arrangements with third-party distributor/maintainer
- International: Parameters being developed
Version 2 Code Leak-Before-Break Applications Sensivity Studies Focus: Identify which models and inputs contribute most to uncertainty and spread in the output NRC/RES approach developed and exercised through study of V.C. Summer and Tsuruga Findings: Top 3 parameters (all are inputs to PWSCC initiation models)
Proportionality constant Proportionality constant multiplier Welding residual stress at the inside diameter NRC/RES approach compared to EPRI-sponsored approaches The following methods were considered adequate and provided similar results:
Structural Integrity Associates: Most Probably Failure Point Direction Cosines, Degree of Separation Dominion Engineering: Machine learning: Gradient Boosting Decision Trees, Random Forest Decision Trees, Linear Support Vector Machines Engineering Mechanics Corporation of Columbus: Linear or Rank Stepwise Regression, Recursive Partitioning, Multivariate Adaptive Regression Splines Piping Systems Analyses Focus:
Generate system-level leak-before break results (i.e., consider multiple welds)
Exercise proposed acceptance criteria Assess effects of enhanced inspection and mitigation techniques NRC/RES results to be compared with independently generated results sponsored by EPRI