Structural Reliability: Fabrication Flaws in Reactor Pressure Vessels
Unmanaged aging and radiation-induced embrittlement in nuclear power plant reactor pressure vessels can impact electrical energy distribution. Researchers at the PNNL are assisting the U.S. Nuclear Regulatory Commission by developing a method for estimating the distribution of flaws in the weld, base metal, and cladding of reactor pressure vessels.
The new method is founded on an empirical data base of PNNL measurements of flaws detected in reactor vessel material from cancelled nuclear power plants. PNNL researchers co-developed the Prodigal Weld Simulation Model. Using the data and Prodigal model, the researchers were able to predict the number and sizes of the thousands of small flaws and a relatively small number of larger flaws. The larger flaws were mainly associated with repair welding and were complex in shape and orientation.
To supplement the data, the researchers collected information from experts on vessel fabrication, welding and inspection procedures. These data expanded the knowledge base on vessel flaws and provided information consistent with PNNL's empirical data.
Through this research, plant operators have greater assurance of reactor vessel integrity as well as improved bases for regulations and rule making and justification for continued plant operation.