Deployment of a Margin Model at Comanche Peak

1. Deployment of a Margin Model at Comanche Peak Presented By: John Meyer TXU Power TXU Power is not the same company as TXU Electric Delivery and is not regulated by the Public Utility Commission of Texas, and you do not have to buy TXU Power’s products to continue to receive quality regulated services from TXU Electric Delivery.

2. Overview of the presentation: • Background and analysis • Model design and development • Implementation – procedure changes and training • Looking forward

3. In the beginning… • INPO identified an Area for Improvement: • “During preparation of several modifications and calculations, factors that could influence design and operating margins were not thoroughly identified and evaluated by engineering personnel or effectively communicated to station operators.

4. Although the station focuses on configuration control when addressing modifications, the impact of changes to design and operating margins is not addressed consistently.” • This AFI was identified during the 2002 E&A which piloted the new Operating Excellence Outcome format

5. Causes/Contributors identified by INPO: • A thorough approach to margin impacts was taken in such instances as reactor core and MOV analysis; less consistent behavior was evidenced during less structured activities • Explicit expectations for margin identification and documentation were not defined

6. Causes/Contributors (continued): • Engineering training forums were primarily focused on design requirement and basis documentation issues; additional focus on margins could promote consistent behaviors in margin documentation • Operations personnel assigned to review modifications could provide insights on actual equipment performance and acceptable operating margins

7. The AFI Resolution Process: • ADDIE! The Systematic Approach to Life… • Analyze • Design • Develop • Implement • Evaluate

8. Definition of Margin A spare amount or measure or degree allowed or given for contingencies or special situations. From Webster

9. An automotive perspective on margin… • The Porsche 911 engine: • Originally sized at 2.0 liters displacement • Deliberately designed with a margin sufficient to accommodate possible capacity increases up to about 2.7 liters

10. Years later, Dr. Ferry Porsche observes: • “Had I known, at that time, that the unit could actually be stretched to 3.3 liters and still be completely reliable, even in racing form, I would almost certainly have decided that it was unnecessarily large and heavy, and would have asked the designers to scale it down. Now I am glad I didn’t!”

11. Terms of Understanding Failure Ultimate Tech Spec Limit Design Limit Limits How do these terms relate to one another or my job? Design Allowable Design Margin Operating Margin Operating Limit Analytical Margin Safety Margin Economic Margin

12. Questions • Do each of the words have a single definition? • Can a specific combination of two or more terms mean different things for different circumstances? • Is this academia or experience based? • Is there an industry standard or concept to be applied on the use or combined use of these terms?

13. So what is the difference between the as-analyzed condition and maximum allowable condition? Margin Analytical Margin? Implicit Design Margin? Explicit Design Margin? Margin of Circumstances?

14. The outcome of the “Analysis” stage: • The primary approach to enhancing margin • management at Comanche Peak would be to • develop and implement a Margin Model

15. The Margin Model Design and Development Odyssey

17. The Operating Excellence Outcome and Enablers [CM-1] Plant equipment configuration is maintained consistent with design and licensing requirements Well-Managed and Understood Safety, Design, and Operational Margins [CM-2] Plant activities are conducted in a manner that maintains configuration control and operating and design margins [CM-3] Processes used to control plant configuration, design, and licensing bases are clearly defined and implemented properly

18. INPO Model - 2003 Functional/Design Failure Greater than design basis range Design margin ( This is a prohibited range of operation and represents the additional conservative margin to account for uncertainties in design and construction ) Design or Tech Spec Basis Limit Analyzed transient range ( Design allows operation in the transient range. However operating restrictions consistent with the design, such as the magnitude and frequency of excursions into this range apply) Operating Point Limit Operating margin Allowed operating range ( The allowed operating range provides the normal margins operators use without violating setpoints ) Normal Operating Point

19. Everything but the Kitchen Sink: Functional/Design Failure Functional Failure NO Margin Design Failure Safety Margin Allowable (Design Limit) AvailableAnalyticalMargin Less than Allowable Results of Analysis Design Basis Limit “Explicit” Design Margin Action Statement Analyzed Transient Range Tech. Spec. Limit Limiting Condition for Operation (LCO) satisfied Licensing / TS Margin Operating Limit Allowed Operating Range Normal Operating Margin Normal Operation

20. Yet Another Margin Model Ultimate Capability Design Allowable Requirements Design Basis Limit or TS Limit Operating Limit Normal Operations Operating Margin Operating Margin Design Margin Safety Margin

21. INPO Design Engineering Managers Workshop - August, 2003 • Comanche Peak presented much of the previous material • Conducted a lengthy afternoon breakout, resulting in a consensus on an appropriate model

22. Upon return to Comanche Peak: • Over a period of several weeks, interfaced with a Duke Power group developing a margin model, ultimately merging on concepts philosophically consistent with the INPO workshop consensus • Corralled Comanche Peak Design Engineering Analysis personnel into a conference room…

23. The objective: We don’t leave until we have reached consensus on a Comanche Peak Margin Model • The process: Summarize previous work, review industry input, share individual opinions, and make a decision • Two criteria: Simple; portrays Operational, Design, and Safety Margin • The Design Engineering Analysis Manager’s perspective – Herding Cats • The result…

24. CPSES Margin Model Safety Margin Ultimate Capability Design Limit Design Margin Current Operating Conditions Operational Margin Operating Limits

25. Definitions: • Analytical Margin - Usable Design Margin that is contained within design calculations in the form of conservative methodology, assumptions, and other provisions. • Design Limit - The Design Function acceptance criteria.

26. Definitions (continued): • Design Margin - That margin between the Operating Limit of a structure, system or component and the Design Limit. • Margin Management - Control of Design Margins and Operating Margins.

27. Definitions (continued): • Operating Limit - The upper or lower limit of operation of a structure, system or component established by Engineering. • Operating Margin - The difference between the range of normal operation of a structure, system or component and the Operating Limit.

28. Definitions (continued): • Safety Margin - That margin between the Design Limit and the ultimate capability (i.e., the point at which failure to perform a design function is likely) of a structure, system or component.

29. Some examples of Model application

30. Cat. I Structure Pinch Points: Current Design

31. Starting Voltage Model

32. Starting Voltage - Nonconformance

33. Starting Voltage - New Assumptions

34. Implementation: Procedure Changes • Added clarification notes to the overall Design Control procedure • Added a requirement to the design change procedure to explicitly address operating and design margin considerations in design change engineering bases • Added a requirement to the calculation procedure to address and document margin considerations in calculations

35. Implementation: Introductory Training • Engineering personnel – conducted accredited training for design qualified personnel • Shift Operations personnel – introduced the model during a Licensed Operator Requalification Training cycle • Maintenance management – introduced the model via e-mail distribution

36. Where do we go from here? • Evaluate effectiveness • Conduct periodic refresher training • Train new Engineering and Shift Operations personnel • Integrate into ongoing configuration management initiatives • Maintain momentum

37. Final Perspective • Margin management must be internalized; this is facilitated by a simple, visual model • Internalization will reinforce a questioning attitude toward potential margin impacts across the station • A focus on margin management will promote sensitivity toward station configuration control