ML021080211
| ML021080211 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/06/2002 |
| From: | Mccollum W Duke Energy Corp |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML021080211 (11) | |
Text
1 Achieving Operating Nuclear Excellence RIC 2002 Session W1 Circumferential Cracking of Reactor Pressure Vessel Head Penetration Nozzles Industry Experience: Management of RV Head Penetration PWSCC at Oconee Nuclear Station William R McCollum, Jr.
Vice President, Oconee Nuclear Station Duke Energy March 6, 2002
2 Achieving Operating Nuclear Excellence Configuration of RV Head Insulation and Location of Inspection Ports
3 Achieving Operating Nuclear Excellence Impact to Oconee Nuclear Station
- Loss of Unit Reliability
- Leakage events must be repaired
- 75 days of lost generation in repairs alone
- Radiation Exposure
- ~ 413 rem of unplanned personnel radiation exposure
- Workforce and staffing challenges
- RPV Head Replacement
- Spring 2003 Oconee Unit 3
- Fall 2003 Oconee Unit 1
- Spring 2004 Oconee Unit 2
4 Achieving Operating Nuclear Excellence Evolution of Top of the RPV Head Bare Metal Visual Inspections
- Amount of boric acid crystals around penetrations can be very small and in some cases < 1/2 cubic inch
- Leakage may appear as popcorn pushed up around the nozzle, or as a string coming from the annulus, or as flow
- All boric acid deposits should be cleaned from head each outage
5 Achieving Operating Nuclear Excellence Oconee Unit 3, March 2001, RV Head After Cleaning 11*
6 Achieving Operating Nuclear Excellence Evolution of Ultrasonic Inspection Techniques
- Techniques for detection and sizing of ID flaws is now well developed
- Developed blade probe capability to search for OD circumferential indications
- Improved analysis techniques and delivery systems to increase detectability of OD nozzle cracks
7 Achieving Operating Nuclear Excellence Evolution of Repair Techniques
- Repairs during ONS-1 RFO and ONS-3 Maintenance Outage accomplished by manual excavation and welding
- The ID Temper Bead repair technique
- First demonstrated for ONS-2 repairs
8 Achieving Operating Nuclear Excellence Evolution of Repair Techniques
- The ID Ambient Temper Bead was developed in time for the ONS-3 Fall 2001 refueling outage
- ASME Relief Requests were needed for all repair methods
9 Achieving Operating Nuclear Excellence Lessons Learned
- Significant progress has been made in a short period of time
- Alloy 600 material is very flaw tolerant and even when cracks develop the material maintains significant structural capacity
10 Achieving Operating Nuclear Excellence Lessons Learned
- Management of PWSCC in the RPV closure head penetrations is a long term undertaking
- Less dose intensive methods for performing the inspections must be developed and the capabilities demonstrated
11 Achieving Operating Nuclear Excellence Lessons Learned
- Clear and frequent communication with NRC Staff is imperative
- Better automated repair methods must be developed and demonstrated
- Develop management plans for other Alloy 600 locations in contact with primary water