Expanded Materials Degradation Assessment (EMDA): Aging of CoreInternals and Piping Systems (NUREG/CR-7153, Volume 2)

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Publication Information

Manuscript Completed: October 2013
Date Published: October 2014

Prepared by Expert Panel:
Peter Andresen, General Electric; Koji Arioka, Institute of Nuclear
Safety Systems; Steve Bruemmer, Pacific Northwest National
Laboratory; Jeremy Busby, Oak Ridge National Laboratory;
Robin Dyle, Electric Power Research Institute; Peter Ford,
General Electric-Retired, Karen Gott, Swedish Nuclear Power
Inspectorate-Retired; Amy Hull, U.S. Nuclear Regulatory
Commission; and Roger Staehle, Staehle Consulting

On behalf of:
Oak Ridge National Laboratory
Managed by UT-Battelle, LLC

J. T. Busby, DOE-NE LWRS EMDA Lead.

P. G. Oberson and C. E. Carpenter, NRC Project Managers
M. Srinivasan, NRC Technical Monitor

Prepared for:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


In NUREG/CR-6923, "Expert Panel Report on Proactive Materials Degradation Assessment," referred to as the PMDA report, NRC conducted a comprehensive evaluation of potential aging-related degradation modes for core internal components, as well as primary, secondary, and some tertiary piping systems, considering operation up to 40 years. This document has been a very valuable resource, supporting NRC staff evaluations of licensees' aging management programs and allowing for prioritization of research needs.

This report describes an expanded materials degradation assessment (EMDA), which significantly broadens the scope of the PMDA report. The analytical timeframe is expanded to 80 years to encompass a potential second 20-year license-renewal operating-period, beyond the initial 40-year licensing term and a first 20-year license renewal. Further, a broader range of structures, systems, and components (SSCs) was evaluated, including core internals, piping systems, the reactor pressure vessel (RPV), electrical cables, and concrete and civil structures. The EMDA uses the approach of the phenomena identification and ranking table (PIRT), wherein an expert panel is convened to rank potential degradation scenarios according to their judgment of susceptibility and current state of knowledge. The PIRT approach used in the PMDA and EMDA has provided the following benefits:

  • Captured the status of current knowledge base and updated PMDA information,
  • Identified gaps in knowledge for a SSC or material that need future research,
  • Identified potential new forms of degradation, and
  • Identified and prioritized research needs.

As part of the EMDA activity, four separate expert panels were assembled to assess four main component groups, each of which is the subject of a volume of this report.

  • Core internals and piping systems (i.e., materials examined in the PMDA report) – Volume 2
  • Reactor pressure vessel steels (RPV) – Volume 3
  • Concrete civil structures – Volume 4
  • Electrical power and instrumentation and control (I&C) cabling and insulation – Volume 5

This volume summarizes the results of expert panel assessment of the aging and degradation of core internals and piping materials of nuclear power plants (NPPs). The work was conducted via a partnership between the NRC and the DOE's Light Water Reactor Sustainability (LWRS) program to extend NRC's Proactive Materials Degradation Assessment (PMDA), NUREG/CR-6923. The main objective of the work described herein was to identify core internal and primary piping components of NPPs where degradation is likely to occur, or may have occurred, to define relevant aging and degradation modes and mechanisms, and to perform systematic assessment of the effects of this aging related degradation on the future life of those components, drawing on the knowledge and expertise of the above-cited panel. The approach adopted by the panel is based on the Phenomena Identification and Ranking Table (PIRT) process.

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