ML040980394
| ML040980394 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 03/11/2004 |
| From: | Jury K Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML040980394 (6) | |
Text
Extended Power Uprate Licensing Challenges Exelon Nuclear Keith Jury, Director - Licensing and Regulatory Affairs Regulatory Information Conference 2004 Session W6 March 11, 2004
2 Background
- NRC approved 17% extended power uprate (EPU) for Dresden and Quad Cities in 2001, and modifications were implemented in 2001-2002
- Two major categories of EPU issues since implementation
- Vibration effects
- Steam dryer failures
- Main steam relief valve degradation
- One example of small bore piping failure
- Feedwater sample probe failures
- Reduced operating or safety margin
3 Licensing Process Issues Approved EPU topical reports do not provide sufficient guidance on the depth or focus of analyses required, especially concerning vibration Effects of core design and fuel transitions, combined with EPU, may result in unanticipated cycle-specific analysis results
- Example is requirement for additional safety valve at Dresden Review of previous generic communications and operating experience (OE) information for EPU needs to be more thorough
- EPU exacerbated condition reported in GE Service Information Letter (SIL) on main steam line low pressure isolation setpoint margin
- SIL regarding sample probe failures was thought to be unaffected by EPU BWRVIP documents regarding steam dryers and effects of loose parts require re-evaluation/revision
4 Regulatory Implications NRC confidence in the EPU licensing process has eroded
- Extensive high level interactions with NRC management
- Additional NRC information and review requests
- Letters of expectation and commitment confirmation
- Recognized need to revise safety evaluation for previous EPU amendment NRC has shown increased sensitivity toward potential EPU impact on licensing actions and plant issues Licensing process is still robust
- Safety analysis acceptance criteria are verified to be met
- Issues to date have not been safety significant Issues show there is some uncertainty when moving into previously uncharted territory
- Uncertainty is mitigated through sharing of OE, similar to experience gained during early stages of nuclear industry Emphasizes need for continued focus on effective use of industry OE
5 Exelon and Industry Response
- Exelon and industry EPU evaluation
- Exelon has undertaken several in-depth reviews to prevent additional unexpected outcomes
- BWR Owners Group committee on EPU effects
- BWR Owners Group subcommittee and BWRVIP working group on steam dryers
6 Conclusion
- EPUs have produced significant benefit to the industry by increasing generation at acceptable costs
- Unexpected issues clearly demonstrate the need to make adjustments in the analyses and reviews
- NRC sensitivity toward potential EPU impacts has increased significantly
- Implications are manageable through a combination of more detailed up-front analyses and continued effective use of OE