Damage Assessment Technologies for Prognostics and Proactive Management of Materials Degradation (PMMD)
There are approximately 440 operating reactors in the global nuclear power plant (NPP) fleet with an average age greater than 20 years and design lives of 30 or 40 years. The United States is currently implementing license extensions of 20 years on many plants, and consideration is now being given to the concept of "life-beyond-60", license extension from 60 to 80 years and potentially longer. In almost all countries with NPPs, authorities are looking at some form of license renewal program. In support of NPP license renewal over the past decade, various national and international programs have been initiated. This paper discusses stressor-based prognostics and its role as part of emerging trends in Proactive Management of Materials Degradation (PMMD) applied to nuclear power plant structures, systems and components (SSC). The paper concisely explains the US Nuclear Regulatory Commission’s (NRC) program in PMMD, the basic principles of PMMD and its relationship to advanced diagnostics and prognostics. It then provides an assessment of the state of maturity for diagnostic and prognostic technologies, including NDE and related technologies for damage assessment, and the current trend to move from condition-based maintenance to on-line monitoring for advanced diagnostics and stressor-based prognostics. This development in technology requires advances in sensors; better understanding of what and how to measure within a nuclear power plant; enhanced data interrogation, communication and integration; new prediction models for damage/aging evolution; system integration for real-world deployments and quantification of uncertainties in what are inherently ill-posed problems. Stressor-based analysis is based upon understanding which stressor characteristics (e.g., pressure transients) provide a percussive indication that can be used for mapping subsequent damage due to a specific degradation mechanism. The resulting physical damage and the associated decrease in asset performance start with the application of a stressor to the component. The design engineer sets the desired operational stressor intensity level so that the degradation in the physical state of the component occurs slowly enough for the equipment to last for its required design life. In general, when the design limit of a stressor is exceeded (during operation), the component life expectancy starts to shorten. Conversely, careful control of operational parameters can enable extension of component life beyond that normally expected. For systems which were conservatively designed (such as nuclear power plants), the premise of the prognostic methodology is that a relationship can be derived that will allow a much more accurate projection of the remaining useful life. This is achieved by focusing on trending the stressor characterics rather than trending a performance metric. In this trend analysis example, the slope of the trended parameter is thought to give a measure of the degradation rate of the component performance. This is assumed to be a function of the rate of decline in the physical integrity of the equipment. Experience from measurements has shown this assumption to be true if one accounts for the nonlinearity which can occur between physical attributes and their effects on performance.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 978524
- Report Number(s):
- PNNL-SA-64157; TANSAO; 401001060; TRN: US1002989
- Journal Information:
- Transactions of the American Nuclear Society, 100(1):215-217, Vol. 100, Issue 1; ISSN 0003-018X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
29 ENERGY PLANNING
POLICY AND ECONOMY
43 PARTICLE ACCELERATORS
COMMUNICATIONS
DESIGN
ENGINEERS
FOCUSING
FORECASTING
MAINTENANCE
MANAGEMENT
MONITORING
NUCLEAR POWER
NUCLEAR POWER PLANTS
PERFORMANCE
SERVICE LIFE
SUPERCONDUCTING SUPER COLLIDER
TRANSIENTS
NDE
Material Degradation