R645.1 Statistical modelling of aging effects in failure rates of piping components

There is a general trend towards the use of risk-informed assessment of systems, structures and components in areas where complex technologies are in operation. The use of quantitative risk and reliability analysis to support structural integrity as a foundation for rational decision making has been found in increasing number of engineering areas, e.g., aviation and space industries, nuclear technologies, oil and gas exploration and transportation, amongst others. However, there are number of concerns with risk-informed decision making and use of statistical and probabilistic models, techniques and tools. Some of those concerns and limitations in practical application of those models include: modeling uncertainties, the tails of failure probability distributions, availability and access to relevant data, validation of statistical models and defining acceptance criteria, inclusion of ageing effects, completeness and rigor or lack of it in application of statistical models.

The Operational Engineering Assessment Division (OEAD) is actively pursuing the development of a generic guidance document together with associate methods and techniques to pursue statistical operability determination of events involving degraded of failed metallic (e.g., carbon steel) passive components. A key element of the potential risk-informed operability determinations shall be the application of statistical reliability and structural integrity models based on relevant operational experience in internationally recognized engineering databases. Such a risk-informed approach should include the explicit utilization of statistically defined acceptance criteria as utilized today in nuclear and other complex technologies.

This project fits under the Fitness for Service Research Program Area (E-DOCS-#4401886) within the Aging Management Sub-Program Area.

2.0 Objectives

The objective of this work is to support the development of operability determination guidelines of best industry practices and to facilitate practical application of statistical and probabilistic methods for the failure rates and related fitness-for-service assessment of systems, structures, and components.

3.0 Scope of Work

The Contractor will be required to develop a “Technical Manual / Guide for Risk-Informed Assessment of Carbon Steel Passive Component Reliability and Fitness-for-Service.” The proposed scope of work will be performed in a phased manner over a period of 36 months from the beginning of the project. The proposed Technical Manual (TM) will document the underlying theory and associated methods and techniques for performing risk characterization of carbon steel passive components that exhibit structural degradation such a non through-wall and through-wall defects. The project will include applicable acceptance criteria, range of analytical templates for assessment of aging factors as well as the determination of incremental changes in plant risk by degraded passive component states.

4.0 Tasks to be Performed

The Technical Manual (TM) or Guide should document the underlying theory and associated methods and techniques of risk-informed passive component reliability. Specifically, this TM should build on the utilization of advanced statistical models of passive component reliability on the basis of recognized and accessible passive component engineering operational experience and material degradation models and experimental evidence. Included in the TM shall be an extensive glossary of technical terms that specifically captures all aspects of statistical and probabilistic structural integrity and fitness-for-service assessments. The following specific tasks shall be performed:

1.1 Overview of regulated industries practices with risk-informed operability determinations across different industries. Regulatory requirements and industry practices, as a minimum, should discuss US Nuclear Regulatory Commission, Environmental Protection Agency, US National Aeronautical and Space Administration, relevant authorities from European and Nordic countries. The contractor is encouraged to include references to other industries (oil, gas, marine, civil engineering, etc.,)

1.2 Development of the TM. This work shall build on the existing body of insights and results of applications. This task needs to clearly acknowledge and address real-world applications involving the direct utilization of a pedigreed passive component failure. The TM shall include a set of review check lists especially developed for use by OEAD analysts.

1.3 TM Validation and Demonstrations. This aspect of the proposed project shall demonstrate the practical application of TM methods & techniques, such as:

a. Fitness-for-service evaluations of piping system components using advanced statistical models. Given the discovery of a degraded carbon steel piping component, this sub-task provides the step-by-step instructions for performing a risk-characterization; e.g. change in core damage frequency and large early release frequency.

b. Effect of different integrity management strategies (e.g., leak detection, leak test, non-destructive examination) on piping integrity. This sub-task addresses a practical application of modern statistical reliability models to structural integrity assessments.

c. Aging management assessment of carbon steel passive components. This sub-task addresses the application of advanced statistical reliability models to the determination of quantitative aging factors.

d. Given the importance of passive components for operation of a plant, the TM should present details on modeling of operability determination including the factors that must be considered and how the statistical/ probabilistic fitness-for-service assessment should be performed.

e. The Contractor is expected to expand on the content based on her/his technical expertise and proposal to approach this project topic.

1.4 Workshops. One-day workshops shall be conducted upon completion of each of the above three TM Demonstrations (as specified in 1.3 a, b, and c).

1.5 Documentation. Upon completion of Tasks 1 through 4, a Technical Manual/ Guide shall be prepared to document inputs, outputs, assumptions, methodology and results.

1. Background