United States Nuclear Regulatory Commission - Protecting People and the Environment

Expanded Materials Degradation Assessment (EMDA): Executive Summary of EMDA Process and Results (NUREG/CR-7153, Volume 1)

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Publication Information

Manuscript Completed: October 2013
Date Published: October 2014

Prepared by:
J. T. Busby
Oak Ridge National Laboratory

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

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Abstract

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 agingrelated 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

Factors considered in the assessment included the reactor environment, existing operational experience and laboratory data and models of materials behavior. Each separate assessment provided an analysis of key degradation modes for current and expected future service, key degradation modes expected for extended service, and suggested research needs to provide technical information for operation up to 80 years. The scope, background, and analysis for each of these four areas are described in detail in other companion volumes. This volume provides a summary of the findings in each panel.

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