Application of reliability techniques to prioritize BWR (boiling water reactor) recirculation loop welds for in-service inspection

Technical Report · Fri Dec 01 00:00:00 EST 1989

DOI:https://doi.org/10.2172/5193479· OSTI ID:5193479

Holman, G. S. ^[1]

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1. Lawrence Livermore National Lab., CA (USA)

In January 1988 the US Nuclear Regulatory Commission issued Generic Letter 88-01 together with NUREG-0313, Revision 2, Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping,'' to implement NRC long-range plans for addressing the problem of stress corrosion cracking in boiling water reactor piping. NUREG-0313 presents guidelines for categorizing BWR pipe welds according to their SCC condition (e.g., presence of known cracks, implementation of measures for mitigating SCC) as well as recommended inspection schedules (e.g., percentage of welds inspected, inspection frequency) for each weld category. NUREG-0313 does not, however, specify individual welds to be inspected. To address this issue, the Lawrence Livermore National Laboratory developed two recommended inspection samples for welds in a typical BWR recirculation loop. Using a probabilistic fracture mechanics model, LLNL prioritized loop welds on the basis of estimated leak probabilities. The results of this evaluation indicate that riser welds and bypass welds should be given priority attention over other welds. Larger-diameter welds as a group can be considered of secondary importance compared to riser and bypass welds. A blind'' comparison between the probability-based inspection samples and data from actual field inspections indicated that the probabilistic analysis generally captured the welds which the field inspections identified as warranting repair or replacement. Discrepancies between the field data and the analytic results can likely be attributed to simplifying assumptions made in the analysis. The overall agreement between analysis and field experience suggests that reliability techniques -- when combined with historical experience -- represent a sound technical basis on which to define meaningful weld inspection programs. 13 refs., 8 figs., 5 tabs.

• Research Organization: US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Div. of Engineering; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USNRC
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5193479
• Report Number(s): NUREG/CR-5486; UCID-21838; ON: TI90005357; TRN: 90-004352
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
22 GENERAL STUDIES OF NUCLEAR REACTORS
BWR TYPE REACTORS
REACTOR COOLING SYSTEMS
WELDED JOINTS
IN-SERVICE INSPECTION
COMPUTERIZED SIMULATION
FAILURE MODE ANALYSIS
FORECASTING
FRACTURE MECHANICS
HEAT TRANSFER
HYDRAULICS
LEAKS
LOSS OF COOLANT
P CODES
PIPES
PROBABILISTIC ESTIMATION
REACTOR LICENSING
REACTOR SAFETY
RELIABILITY
RISK ASSESSMENT
TECHNOLOGY ASSESSMENT
ACCIDENTS
COMPUTER CODES
COOLING SYSTEMS
ENERGY SYSTEMS
ENERGY TRANSFER
FLUID MECHANICS
INSPECTION
JOINTS
LICENSING
MECHANICS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTORS
SAFETY
SIMULATION
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
WATER COOLED REACTORS
WATER MODERATED REACTORS
210100* - Power Reactors
Nonbreeding
Light-Water Moderated
Boiling Water Cooled
210700 - Nuclear Power Plants- Regulation & Licensing
990200 - Mathematics & Computers
220900 - Nuclear Reactor Technology- Reactor Safety