05000277/LER-2006-003, Regarding Elbow Leak on Piping Attached to Suppression Pool Results in Loss of Containment Integrity
| ML063420059 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/04/2006 |
| From: | Grimes J Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 06-003-00 | |
| Download: ML063420059 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2772006003R00 - NRC Website | |
text
Exeln.,
Exelon Nuclear www.exeloncorp.com Nuclear Peach Bottom Atomic Power Station 1848 Lay Road Delta, PA 17314-9032 1 OCFR 50.73 December 4,2006 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 3 Facility Operating Ucense No. DPR-44 NRC Docket No. 50-277
Subject:
Licensee Event Report (LER) 2-06-03 This LER reports a condition involving a Technical Specifications required shutdown for an inoperable Primary Containment as a result of a leak discovered on the High Pressure Coolant Injection return piping to the Torus. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations.
The specific methods that are planned to restore and maintain compliance are discussed in the LER. If you have any questions or require additional information, please do not hesitate to contact us.
Sincerely, Joseph P. Grimes Plant Manager Peach Bottom Atomic Power Station JPG/djf/IR 541265 Attachment cc:
PSE&G, Financial Controls and Co-owner Affairs R. R. Janati, Commonwealth of Pennsylvania INPO Records Center S. Collins, US NRC, Administrator, Region I R. I. McLean, State of Maryland US NRC, Senior Resident Inspector CCN 06-14082
N4RC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 6-2oo4)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information digits/characters for each block) olcin
- 3. PAGE Peach Bottom Atomic Power Station Unit 2 05000277 1 OF 4
- 4. TITLE Elbow Leak on Piping Attached to Suppression Pool Results in Loss of Containment Integrity
- 5. EVENT DATE
- 6. LER NUMBER _
- 7. REPORT DATE 1
- 8. OTHER FACILITIES INVOLVED I I I FhUYNM OKTNME MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR I
0500o
__I
_NUMBER NO.
05000I 10 7
2006 06 03 -
0 12 4
2006 05000
- 9. OPERATING MODE "11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 0 20.2201 (b)
[I 20.2203(a)(3)(i)
[3 50.73(a)(2)(i)(C)
[0 50.73(a)(2)(vii) 0 20.2201 (d)
[I 20.2203(a)(3)(ii)
[
50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A)
D 20.2203(a)(1) 03 20.2203(a)(4) 0 50.73(a)(2)(ii)(B)
[0 50.73(a)(2)(viii)(B) 13 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii)
[0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[] 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[0 50.73(a)(2)(x) o 20.2203(a)(2)(iii) 0 50.36(c)(2) 03 50.73(a)(2)(v)(A) 0 73.71 (a)(4) o 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0" 50.73(a)(2)(v)(B)
[0 73.71 (a)(5) 22%
0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER C3 20.2203(a)(2)(vI) 0 50.73(a)(2)(i)(B)
[3 50.73(a)(2)(v)(D)
Specify In Abstract below or in NRC Form 36MA
- 12. MCENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
PBAPS Unit 2, James Armstrong, Regulatory Assurance Manager 717-456-3351CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANCI-REPORTABLE FACTURER TO EPIX IFACTURER TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION [3 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE kBSTRACT (Limit to 1400 spaces, Le., approximately 15 single-spaced typewritten lines)
On 10/7/06 at 1802 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.85661e-4 months <br />, an Unusual Event was declared for Unit 2 as a result of the discovery of a leak at an elbow for piping that penetrates the Primary Containment Suppression Pool (i.e. Torus). The 4" piping is the High Pressure Coolant Injection (HPCI) / Reactor Core Isolation Cooling (RCIC) Torus Flush line. This line is normally isolated from the HPCI / RCIC systems by a closed motor-operated valve and is only used during testing activities. The leak was discovered by an equipment operator at approximately 1741 hours0.0202 days <br />0.484 hours <br />0.00288 weeks <br />6.624505e-4 months <br /> during a planned inspection associated with a RCIC system check valve. The leak occurred on the intrados of a 45 degree elbow of the 4" piping. The elbow was located approximately I foot above the Torus penetration (i.e.
the leak was outside of Primary Containment). The cause of the crack in the elbow is due to cavitation and abrasive erosion and/or localized water-jet cutting resulting from excessively high flow velocities through this piping during test conditions in conjunction with an apparent lack of fusion between the weld backing ring and the weld root at the elbow weld. The leaking elbow was replaced and non-destructive testing was performed.
The similar pipe on Unit 3 was examined and no significant concerns were noted. Extensive walk downs of similar piping that is attached to the Torus was conducted for both Units 2 and 3. There were no similar deficiencies discovered. Selected ultrasonic testing was performed on Unit 2 and 3 Torus attached piping that involved higher flow rates. These examinations also did not identify any similar concerns.
NRC FORM 366 (6-2004)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use addifional copies of NRC Form 366A) (17)
Analysis of the Event, continued Further examination of the leaking elbow noted that axial and circumferential cracking existed at the elbow intrados. Failure analyses of the elbow determined that only minimal leakage existed at the elbow with the as-found indications. This minimal leakage only occurred when the HPCI or RCIC system was being operated in the test mode involving return flow being routed to the Torus.
In the unlikely event that a worst-case design basis event had occurred and the elbow did not maintain its integrity, additional leakage would have occurred. If both subsystems of containment cooling (including containment spray) were used during the design event, the Torus water level would only be minimally impacted. If only one subsystem of containment cooling were used with no containment spray, then water leakage would have occurred until the HPCI / RCIC 'Flush' line became uncovered (approximately 5 feet below normal Torus water level) and a gaseous release could have occurred. The water leakage would be contained within the Torus Room. The gaseous leakage would be processed through the secondary containment and Standby Gas Treatment System. The Torus Room is within the Secondary Containment boundary.
Safety systems operated as designed during the unit shutdown.
Preliminary assessments indicate that this event would not be risk significant.
Corrective Actions
The leaking elbow was replaced and non-destructive testing was performed. The similar pipe on Unit 3 was examined and no significant concerns were noted. Extensive walk downs of similar piping that is attached to the Torus were conducted for both Units 2 and 3. There were no similar deficiencies discovered. Selected ultrasonic testing was performed on Unit 2 and 3 Torus attached piping that involved higher flow rates. These examinations also did not identify any similar concerns.
Plant test procedures were revised to prevent using the HPCI / RCIC Torus Flush line at high flow conditions.
Additional corrective actions including extent of condition evaluations are being evaluated in accordance with the Corrective Action Program.
Previous Similar Occurrences There were no previous similar events identified.