Fabrication Flaw Density and Distribution in the Repairs of Reactor Pressure Vessels

Conference · Wed Feb 15 04:00:00 EST 2006

OSTI ID:991098

Schuster, George J; Doctor, Steven R; Simonen, Fredric A

The Pacific Northwest National Laboratory (PNNL) is developing a generalized flaw size and density distribution for the population of U.S. reactor pressure vessels (RPVs). The purpose of the generalized flaw distribution is to predict vessel specific flaw rates for use in probabilistic fracture mechanics calculations that estimate vessel failure probability. Considerable progress has been made on the construction of an engineering data base of fabrication flaws in U.S. nuclear RPVs. The fabrication processes and product forms used to construct U.S. RPVs are represented in the data base. A validation methodology has been developed for characterizing the flaws for size, shape, orientation, and composition. The relevance of construction records has been established for describing fabrication processes and product forms. The fabrication flaws were detected in material removed from cancelled nuclear power plants using high sensitivity nondestructive ultrasonic testing, and validated by other nondestructive evaluation (NDE) techniques, and complemented by destructive testing. This paper describes research that has generated data on welding flaws, which indicated that the largest flaws occur in weld repairs. Recent research results confirm that repair flaws are complex in composition and may include cracks on the repair ends. Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code for nuclear power plant components requires radiographic examinations (RT) of welds and requires repairs for RT indications that exceed code acceptable sizes. PNNL has previously obtained the complete construction records for two RPVs. Analysis of these records show a significant change in repair frequency.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 991098
• Report Number(s): PNNL-SA-43547; 401001060
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
BOILERS
CONSTRUCTION
DEFECTS
DESTRUCTIVE TESTING
DISTRIBUTION
ENGINEERS
EVALUATION
FABRICATION
FRACTURE MECHANICS
Fabrication
Flaw Density
NUCLEAR POWER PLANTS
Nuclear Reactors
ORIENTATION
PRESSURE VESSELS
PROBABILITY
Pressure Vessels
REPAIR
SENSITIVITY
SHAPE
ULTRASONIC TESTING
VALIDATION
WELDING