ML052140189
| ML052140189 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 03/08/2005 |
| From: | Meister J Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML052140189 (10) | |
Text
Exelon Learnings from Extended Power Uprates Presentation to NRC 2005 Regulatory Information Conference March 8, 2005 Washington DC James R. Meister Exelon Nuclear
Overview
- Operational Challenges from EPU
- Vibration Monitoring and Actions
- EPU Vulnerability Review and Actions
- Steam Dryer Repairs and Replacement 2
Operational Challenges from Dresden / Quad Cities EPU
- Increased steam and feed flow velocities have caused increased pressure pulsations and vibration levels, leading to equipment failures and degradation.
- Steam Dryer Failures
- Main Steam Relief Valve Failure
- Main Steam Line Low Pressure Switch Failure (1/2 Group Isolation)
- Turbine Control Valve Pressure Switch Failure (1/2 Scram)
- HPCI Test Tap Connection Failure
- Main Steam Drain Line Failure
- Feedwater Sample Probe Failure
- Industry data indicates that nearly all EPU related problems are caused by increased vibration.
3
Operational Challenges from D/Q EPU
- Reduction of margin has affected several systems
- Reduction in available Main Steam Safety Valve set point tolerance
- Reduction in Feedwater Heater Drain Emergency Valve capacity
- Previous Standby Feedwater and Condensate Pumps are normally operated
- Reduction in Main Condenser margin 4
Exelon Response to EPU Lessons Learned
- Teams were established to address three major impact areas
- Vibration Impact Resolution
- EPU Vulnerability Review and Actions
- Steam Dryer Repair and Replacement
- Exelon established Technical Human Performance Initiative 5
Vibration Monitoring and Actions
- Monitoring and Performance Evaluations for Critical Subcomponents
- Accelerometers to collect actual vibration data for piping, valves and actuators
- Shaker table testing at Wyle Labs
- Analytical Modeling of affected components
- Resulting Actions
- Adjust PM scope and frequency based on results
- Implemented focused / detailed outage walkdowns
- Identify subcomponent wear and implement modifications for ERV and Target Rock Valves 6
EPU Vulnerability Review
- Comprehensive and rigorous review of systems and components
- Utilized multiple industry organizations
- For the purpose of this review, every component in the plant was assumed to be susceptible to failure, unless proven otherwise
- Evaluated changes in operating parameters post EPU for all 4 units
- Flow rates, temperature, pressure, radiation levels, vibration levels, wear
- Review was conducted both at the system and component levels
- 53 systems included
- Identified potential vulnerabilities due to the changed parameters
- Provided recommendations to address the potential vulnerabilities 7
EPU Vulnerability Review Results
- Reviews confirmed that adequate safety margin exists
- 101 recommendations were made
- 60 require outage inspections over next 4 years
- 9 involve non-outage work
- 32 involve additional analyses or studies
- 27 are Exelon specific
- 74 have potential BWR fleet applicability
- Review results were subject to three independent challenges
- Internal Team Challenges
- Executive Challenge Board
- BWROG Challenge review
- Actions are in progress and Dresden and Quad Cities 8
Steam Dryer Repairs and Replacement
- Enhanced repairs implemented at Dresden 2/3 and Quad Cities 2
- Dryer Replacement Project Initiated
- Develop advanced steam dryer design
- Implement design features to minimize stresses
- Qualify the replacement dryer through testing and analysis
- Instrument the first dryer to verify design loadings
- First installations will be at Quad Cities units 1 & 2 Spring 2005 9
Conclusions
- Adverse effects have been and are being addressed
- Safety margins were confirmed adequate
- Exelon experience has been shared with the industry and with the NRC
- Implementation of recommended actions continues 10