Research Papers: Nuclear Power

Integration of Degradation Models Into Generation Risk Assessment: Challenges and Modeling Approaches

[+] Author and Article Information
Mikko I. Jyrkama1

Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadamjyrkama@uwaterloo.ca

Mahesh D. Pandey

Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada

Stephen M. Hess

 Electric Power Research Institute (EPRI), West Chester, PA 19382


Corresponding author.

J. Eng. Gas Turbines Power 132(10), 102916 (Jul 08, 2010) (8 pages) doi:10.1115/1.4000892 History: Received August 05, 2009; Revised August 20, 2009; Published July 08, 2010; Online July 08, 2010

The main objective of generation risk assessment (GRA) is to assess the impact of equipment unavailability and failures on the ability of the plant to produce power over time. The system reliability models employed for this purpose are based on the standard fault tree/event tree approach, which assumes failure rates to be constant. However, this ignores the impact of aging degradation and results in static estimates of expected generation loss. Component and equipment degradation not only increases the probability of failure over time, but also contributes to generation risk through increased unavailability and costs arising from greater requirement for inspection and replacement of degraded components. This paper discusses some of the key challenges associated with integrating the results of component degradation models into GRA. Because many analytical and simulation methods are subject to limitations, the methodology and modeling approach proposed in this work builds on the current GRA practice using the fault tree approach. The modeling of component degradation can be done separately at the fault tree cut set level, assuming the cut sets are independent and the component unavailabilities are relatively small. In order to capture the joint contribution of equipment failure and unavailability to generation risk, new risk-based importance measures are also developed using the concept of net present value.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Conceptual model of the RIAM process (after Ref. 5)

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Figure 2

Modeling the time-independent and time-dependent cut sets as separate groups

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Figure 3

Simplified fault tree model of a CANDU primary HTS

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Figure 4

Sample results for the annual steam generator tube leak probability, based on the method of Ref. 22

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Figure 5

Sample results for the annual number of tubes required to be plugged, based on the method of Ref. 22



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