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Energy and Environment Directorate

Research Capabilities

Structural Reliability

To maintain the safe operation of nuclear power plants—both nationally and abroad—plant operators must ensure the integrity and continued maintenance of the plants' associated nuclear pressure vessels and piping. PNNL scientists are assisting the U.S. Department of Energy, the U.S. Nuclear Regulatory Commission (NRC), the Electrical Power Research Institute and entities from the commercial nuclear power industry and Hanford Site (Richland, Washington) contractors by performing collaborative research in the area of structural integrity evaluations and decision-making related to important regulatory issues. PNNL is an international leader in the development of probabilistic fracture mechanics methods for predicting the reliability of pressure vessels and piping systems. In addition, PNNL researchers successfully developed a model (based on an extensive series of ultrasonic tests) for estimating the distribution of flaws in the pressure vessel welds, base-metal and cladding that resulted in revision of the NRC rule governing allowable levels of radiation embrittlement.

PNNL also has combined knowledge in vessel reliability and the effectiveness of in-service inspection to develop and apply models that simulate the long-term benefits of periodic inspections of piping systems. Future direction for PNNL structural reliability research includes vessel aging management, plant life extension and licensing of new plant designs; issues related to transportation and storage of spent nuclear fuel and life extension for Hanford Site waste storage tanks. Recently, these same analytical methods were also applied to develop a probability-based design tool for evaluating the structural integrity of automotive glazing systems.


  • Fabrication Flaws in Reactor Pressure Vessels
  • Probabilistic Fracture Mechanics
  • Structural Reliability of Nuclear Pressure Boundary Components

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Energy and Environment

Core Research Areas