Catching the cracks

Catching cracks in nuclear nozzles is no easy task when they are caused by normal stresses and corrosion inside a nuclear reactor. Approximately 70 nozzles per reactor allow control rod drive shafts to pass through the top of a reactor pressure vessel head so that the power level of the reactor can be controlled.

When cracked nozzles were discovered in nuclear power plants in Ohio and Virginia, the Nuclear Regulatory Commission and the Electric Power Research Institute saw an opportunity to evaluate inspecting procedures and eight of these nozzles were selected for study.

Researchers at Pacific Northwest National Laboratory are using state-of-the-art inspection systems that employ nondestructive methods and destructive testing to evaluate the reliability of current inspection procedures. The results of this testing will aid the NRC in determining if improvements are needed for inspecting the nation's 103 operating nuclear power plants. For utilities, these tests provide additional information for making decisions about timing, effectiveness and activities required during reactor maintenance.