ML021070811
| ML021070811 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 04/05/2002 |
| From: | Mel Holmberg NRC/RGN-III/DRS/MEB |
| To: | FirstEnergy Nuclear Operating Co |
| References | |
| FOIA/PA-2003-0018 | |
| Download: ML021070811 (21) | |
Text
NRC AUGMENTED INSPECTION TEAM EXIT MEETING DAVIS-BESSE REACTOR VESSEL HEAD CORROSION APRIL 5, 2002 Slide #1
NRC Augmented Inspection Team Exit Meeting Agenda
- Welcome
- etn Agenda and Structure for Public Involvement
- JIntroduction of NRC and DB3 Personnel
- Purpose of an Augmented Inspection Team
- akgon on Boric Acid Corrosion and Reactor Head Penetration Cracking Slide #2
NRC Augmented Inspection Team Exit Meeting Agenda
- hrcerzto of Reactor Head Inspection Re suits
- Methods and Results for Identifying Reactor Head Corrosion
- Preliminary Causes for Reactor Head Corrosion
- NRC Further Actions
- ocldn Remarks
- Response to Public Questions Slide #3
Typical Pressurized Water Reactor ontrol Pods U
Slide #4
Reactor Vessel Head Degradation Location Control Rod Drive Mechanism N, Area of Davis Besse-Reactor Vessel Head Degradation Reactor Vessel Head Carbon Steel Portion Reactor Vessel Head Insulation Reactor Vessel Head Stainless Steel Cladding Layer Slide #5
Reactor Vessel Head Cavities m 5 Nozzles Cracked; 3 Went All the Way Through the Nozzle Wall
- ecito of Cavity Near Nozzle #3
- Metal Loss Near Nozzle #2 Slide #6
Outer Surface of RPV Head RPV Head J-Groove Weld Schematic Fiqure of TypicalGRDM Nozzle Penetration
Jlos A1 I/
Slide #9
Loss 1%"J Area Loss of Metal 4.21' Reactor Reactor Nozzle Machined Away During Repair Head Slide #10
Missed Opportunities to Identify Corrosion
- otimn Air Cooler Clogging
- otimn Radiation Monitor Filter Clogging
- Boric Acid Buildup and Corrosion on Reactor Head Slide #1 1
Containment Air Cooler Clogging
- Safety System Used to Cool Containment
- JIncrease in Boric Acid Collected on Cooling Coils in 1999
- Change in the Color of Boric Acid Deposits in 1999
- DB Staff Assumed Changes in Volume of Boric Acid Deposits Due to Flange Leakage
- DB Staff Assumed Changes in Boric Acid Color Due to Corrosion of Air Cooler Slide #1 2
- etc Radioactivity in Containment Air from Reactor Coolant Leakage
- einn in May Changes Increased Day 1999, Frequency of Filter from Monthly to Every Other
- itr Clogged with Corrosion Products from Reactor Coolant Leakage Slide #13
Boric Acid Corrosion Control Program
- Required By NRC in 1988 m Sensitive and Reliable Indicator of Reactor Coolant System Leakage
- One Drop per Second (IO.OO1I gpm) Will Leave 15 Pounds of Boric Acid in 1 Year Slide #14
Boric Acid Program Activities
- Ongoing Nozzle Flange Leakage Continued to be a Source of Boric Acid Deposits
- 1990 Modification to Improve Reactor Vessel Head Access Was Not Installed
- eco Vessel Head Boric Acid Deposits Were Not Completely Removed
- Indications of Reactor Vessel Head Corrosion Were Not Recognized or Evaluated Slide #15
Preliminary Root Cause
- avt Caused by Boric Acid Corrosion From Leakage Through Cracks in the Nozzle
- Significant Corrosion Began at Least 4 Years Ago Slide #1 7
Root Cause Areas Yet To Be Addressed
- eemnto of Corrosion Process (Chemistry)
- Role of Deposits Left on Reactor Head
- Role of Reactor Head Temperature on the Rate of Corrosion
- at at Which Cracks and Corrosion Progressed
- Correlation of Davis Besse and Industry Experience Slide #1 8
Confirmatory Action Letter
- Determine the Root Cause
- vlut the Reactor Coolant System for Other Corrosion
- NRC Must Approve Any Repair or Modification m Obtain NRC Restart Approval Slide #19
NRC Further Actions m Special Inspections for Compliance Issues
- Special Inspections for Modifications, Repair or Replacement
- vlutn Implications on Other Plants
- NRC Identifying Improvements to Regulatory Processes and Inspection Programs Slide #20
- Summary and Concluding Remark*,s
- Public Questions and Answers Slide #21
- NRC Website: www.nrc.gov
- Headquarters Operator o-1-800-426-8096 o-1-800-368-5642 o-Tony Mendiola Slide #22