05000455/LER-2014-004, Regarding Reactor Pressure Vessel Head Control Rod Drive Mechanism Penetration Nozzle Weld Indication Attributed to Primary Water Stress Corrosion Cracking
| ML14339A538 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/05/2014 |
| From: | Kearney F Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 1.10.0101, 2.07.0100, BYRON 2014-0149 LER 14-004-00 | |
| Download: ML14339A538 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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 |
| 4552014004R00 - NRC Website | |
text
Exelon Generation Byron Generating Station 4450 North German Church Rd Byron, IL 61010-9794 December 5, 2014 LTR:
BYRON 2014-0149 File:
1.10.0101 2.07.0100 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Unit 2 Facility Operating License No. NPF-66 NRC Docket No. STN 50-455 www.exeloncorp.com
Subject:
Licensee Event Report (LER) 455-2014-004-00, Byron Unit 2 Reactor Pressure Vessel Head Control Rod Drive Mechanism Penetration Nozzle Weld Indication Attributed to Primary Water Stress Corrosion Cracking Enclosed is Byron Station Licensee Event Report (LER) No. 455-2014-004-00 regarding the Byron Station Unit 2 Reactor Pressure Vessel (RPV) Penetration 6 indication identified during 2014 refuel outage B2R18. This condition is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A), any event or condition that resulted in the condition of the nuclear power plant, including its principle safety barriers, being seriously degraded.
There are no regulatory commitments in this report.
Should you have any questions concerning this submittal, please contact Mr. Douglas Spitzer, Regulatory Assurance Manager, at (815) 406-2800.
FAK/GC/sg
Enclosure:
LER 455-2014-004-00 cc:
Regional Administrator NRC Region Ill NRC Senior Resident Inspector Byron Generating Station Respectfully, Faber A.
Site Vice President Byron Generating Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0113112017 (02-2014) s.,
Eshmated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
cc Reported lessons learned are incorporated into the licensing process and ted back to industry.
Send comments regarding burden eshmate to the FOIA, Privacy and Information Collections v
Branch IT-S F53), U S. Nuclear Regulatory Commission, Washington. DC 20555-0001, or by LICENSEE EVENT REPORT (LE R)
Internet e-marl to lrrtocollects.Resource@nro.gov, and to the Desk Officer. Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management end Budget, Washington, DC 20503. If a means used to Impose an information collechon does not display a currenfly valid 0MB digits/characters for each block) control nurnber, the NRC may not conductor sponsor, and a person is not required to respond to, the nfornrahon collection.
- 13. PAGE Byron Station, Unit 2 05000455 1
OF 3
- 4. TITLE Byron Station Unit 2 Reactor Pressure Vessel Head Control Rod Drive Mechanism Penetration Nozzle Weld Indication attributed to Primary Water Stress Corrosion Cracking
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 10 07 2014 2014 004
- - 00 12 05 2014 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[J 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
U 50.73(a)(2)(vii) 6 El 20.2201(d)
[J 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A)
[1 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
[1 20.2203(a)(2)(i)
E] 50.36(C)( 1 )(i)(A)
[1 50.73(a)(2)(iii)
[1 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(o)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[] 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 000 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
Li 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
L] 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
Q 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Speclfyts Abstract below or in
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)
Douglas Spitzer Manager, Byron Regulatory Assurance (815) 406-2800CAUSE SYSTEM COMPONENT FACTURER RFPORTABLE L
CAUSE
SYSTEM COMPONENT FACTIJRER REPORTABLE N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR El YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO SUBION N/A N/A N/A kBSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On October 7, 2014, at 1830 CST, an indication was discovered on Byron Station, Unit 2, Reactor Pressure Vessel (RPV) Penetration No. 6. The indication was located on the outside diameter of the penetration tube and the deepest wall depth was 0.222 inches, approximately 34.11 percent through wall.
The indication was subsequently repaired using the embedded flaw technique in accordance with NRC approved WCAP-15987, Revision 2-A and WCAP-16401, Revision 0. The apparent cause of the indication is attributed to Primary Water Stress Corrosion Cracking. Corrective actions include repair of the indication on Penetration No. 6 and revising the frequency of the Unit 2 volumetric examinations on all 78 RPV penetrations to every refueling outage.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A), any event or condition that resulted in the condition of the nuclear power plant, including it principle safety barriers, being seriously degraded.
NRC FORM 365 (02-201 4)
RC =
A. Plant Condition Prior to Event Event Date/Time: October 7,2014/1830 hours CST Unit 2 - Mode 6
- - Refueling, Reactor Power 0 percent Reactor Coolant System: Ambient Conditions
B. Description of Event
During the Byron Station Unit 2 fall 2014 refueling outage, scheduled volumetric examination of the upper reactor pressure vessel (RPV) head penetrations was performed in accordance with American Society of Mechanical Engineers (ASME) Section Xl Code Case N-729-1 as amended by the conditions within 10 CFR 50.55a(g)(6)(ii)(D).
On October 7, 2014, at 1830 CST, an indication was discovered on Byron Station Unit 2 Reactor Pressure Vessel (RPV) Penetration No. 6. The indication was located on the outside diameter of the penetration tube and was axially oriented with a linear extent of 0.52 inches and a deepest through wall depth of 0.222 inches, approximately 34.11 percent through wall.
A demonstrated volumetric leak path assessment was performed on all 78 of the control rod drive mechanism penetrations in accordance with 10 CFR 50.55a(a)(g)(6)(ii)(D) with no indication of through wall leakage observed. A bare metal visual examination of the exterior surfaces of the reactor head and penetrations was performed in accordance with ASME Section Xl Code Case N-729-1 with no indication of through wall leakage observed.
The indication was subsequently repaired using the embedded flaw technique in accordance with NRC approved WCAP-15987, Revision 2-A and WCAP-16401, Revision 0. The apparent cause of the indication is attributed to Primary Water Stress Corrosion Cracking. Corrective actions include repair of the indication on Penetration No. 6 and revising the frequency of the Unit 2 volumetric examinations on all 78 RPV penetrations to every refueling outage.
C. Cause of Event
be apparent cause of the indication is attributed to Primary Water Stress Corrosion Cracking.
D. Safety Significance
This event is not considered an event or condition that could have prevented fulfillment of a safety function.
The indication was identified in a timely manner and repaired prior to through wall leakage occurring. The flaw was identified as part of a required periodic inspection. Potentially, if the flaw remained undetected, it could have propagated over time through the alloy 600 weld material to form a leak path through the reactor coolant boundary.
E. Corrective Actions
The indication on penetration No. 6 was repaired using the embedded flaw technique in accordance with NRC approved WCAP-15987, Revision 2-A and WCAP-16401, Revision 0 prior to returning the Unit 2 reactor head to service.
The frequency of the Unit 2 volumetric examinations on all 78 RPV penetrations will be revised to be performed every refueling outage in accordance with 10 CFR 50.55a(g)(6)(ii)(D)(5).
F.
Previous Occurrences
Byron Station, Unit 2. Licensee Event Report (LER) 455-2007-001 -00, Reactor Pressure Vessel Head Control Rod Drive Mechanism Penetration Nozzle Weld Indication Due to an Initial Construction Weld Defect Allowing the Initiation of Primary Water Stress Corrosion Cracking, (June 8, 2007).
Byron Station, Unit 1. Licensee Event Report 2011-002-00, Unit 1 Reactor Pressure Vessel Head Penetration Nozzle Weld Flaws Attributed to Primary Water Stress Corrosion Cracking, (May 18, 2011).
A review of these LERs concluded that these events are similar; however, the causes and corrective actions taken would not have been expected to prevent this event from occurring.
Byron Station reported this event through the emergency notification system (ENS) in accordance with 10 CFR 50.72(b)(3)(ii)(A) on October 7, 2014 at 2022 CST.