Nuclear Executive Update   
An EPRI Progress Report, March 2011
TECHNICAL HIGHLIGHTS
Channel Distortion Update: Year 1 Progress

Research results from poolside measurements, hot cell and synchrotron exams and laboratory analyses are being used to improve the models used to guide core design and manage operational aspects of channel distortion.

In 2010, EPRI worked with the nuclear power industry and nuclear fuel vendors to formulate a Channel Distortion Industry Action Plan that outlines a short-term and long-term strategy for addressing channel distortion as an operational issue. Significant progress has been made in the first year of this five-year effort to understand each mechanism of channel distortion at the mechanistic level.

More than half of the 35 boiling water reactors in the United States have reported control blade interference due to channel distortion in the last decade. Affected fuel designs include channels manufactured by all major boiling water reactor fuel vendors. Despite a drop in events during 2010, recent instances of control blade interference indicate that the phenomenon cannot be effectively predicted. The EPRI effort will update guidance on how to manage channel distortion until more effective solutions become available, develop models that can sufficiently predict channel distortion, and help incorporate these models into fuel vendor management tools. Researchers will collect and analyze channel performance data, including operational performance data, poolside dimensional measurements, and hot cell examination data to develop the improved models, and then validate the performance of distortion models via examination and surveillance.

Fuel Channel Bulge Progress over the past year includes:

  • The Institute of Nuclear Power Operations issued updated mitigation guidance for core design and operational practices via Significant Event Report 1-08, Revision 1.
  • An industry-wide database is now being populated with channel distortion data. Preliminary analyses using these data have already resulted in improved models of irradiation growth and shadow corrosion-induced bow that should provide better predictions for current alloys (Zr-2 and Zr-4) and guide development of the next generation of materials.
  • Advanced hot cell examinations have begun on channel coupons from previous projects using electron microscopy to increase the understanding of channel distortion.
  • A test reactor experiment has begun to understand the effects of hydrogen on irradiation growth.
  • Ab initio (atomistical modeling) studies have commenced on the atomistical effects of hydrogen and hydrides in various irradiated zirconium alloys.
  • Technology development is underway for assessing hydrogen content nondestructively.
  • A laboratory shadow corrosion test is being developed to study water chemistry effects and alloy sensitivity.
  • Several poolside surveillance campaigns are underway or planned in both the United States and Europe.

For more information, contact Erik Mader at 208-881-9225 or emader@epri.com.