05000324/LER-2014-002, Regarding Secondary Containment Loss of Safety Function Due to Opening in Reactor Building Roof Drain Piping
| ML14188B455 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  (DPR-062) |
| Issue date: | 06/19/2014 |
| From: | Hamrick G Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BSEP 14-0064 LER 14-002-00 | |
| Download: ML14188B455 (6) | |
| 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 |
| 3242014002R00 - NRC Website | |
text
DUKE
- ENERGY, George T. Hamrick Vice President Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461 o: 910.457.3698 10 CFR 50.73 JUN 1 9 2014 Serial: BSEP 14-0064 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Brunswick Steam Electric Plant, Unit No. 2 Renewed Facility Operating License No. DPR-62 Docket No. 50-324 Licensee Event Report 2-2014-002 In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Duke Energy Progress, Inc., submits the enclosed Licensee Event Report (LER). This report fulfills the requirement for a written report within sixty (60) days of a reportable occurrence.
This document contains no regulatory commitments.
Please refer any questions regarding this submittal to Mr. Lee Grzeck, Manager - Regulatory Affairs, at (910) 457-2487.
Sincerely, George T. Hamrick GTH/mkb
Enclosure:
Licensee Event Report
U.S. Nuclear Regulatory Commission Page 2 of 2 cc (with enclosure):
U. S. Nuclear Regulatory Commission, Region II ATTN: Mr. Victor M. McCree, Regional Administrator 245 Peachtree Center Ave, NE, Suite 1200 Atlanta, GA 30303-1257 U. S. Nuclear Regulatory Commission ATTN: Ms. Michelle P. Catts, NRC Senior Resident Inspector 8470 River Road Southport, NC 28461-8869 U. S. Nuclear Regulatory Commission ATTN: Mr. Andrew Hon (Mail Stop OWFN 8G9A) (Electronic Copy Only) 11555 Rockville Pike Rockville, MD 20852-2738 Chair - North Carolina Utilities Commission P.O. Box 29510 Raleigh, NC 27626-0510
NJRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01131/2017 102-2014)
Estimated 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 />.
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections LICENSEE EVENT REPORT (LER)
Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects.Resource@nrc.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 and Budget, Washington, DC digits/characters for each block) 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Brunswick Steam Electric Plant (BSEP), Unit 2 05000324 1 OF 4
- 4. TITLE Secondary Containment Loss of Safety Function due to Opening in Reactor Building Roof Drain Piping
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER M AYEAR NUMBER NO.
05000 FACILITY NAME DOCKET NUMBER 04 20 2014 2014 -
002 00 06 19 2014 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[E 20.2201(b)
[I 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
El 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 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)
_ 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71 (a)(4) 100 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5) 100 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[
50.73(a)(2)(v)(C)
El OTHER
_ _ 20.2203(a)(2)(vi)
[
50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract bAlow or in
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
Background
Initial Conditions At the time of the event, Unit 2 was in Mode 1, at 100 percent of rated thermal power (RTP). No structure, systems or components were out of service at the time of this event that contributed to this event.
Reportability Criteria This condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. The Secondary Containment [NG] was considered inoperable per Technical Specification (TS) requirements after the determination that the identified leak area exceeded the allowable leakage margin of the Secondary Containment pressure boundary. The NRC was initially notified of this event on April 20, 2014 (i.e.,
Event Number 50046), in accordance with 10 CFR 50.72(b)(3)(v)(C). In accordance with the guidance of NUREG-1022, Event Reporting Guidelines 10 CFR 50.72 and 50.73, Revision 3, TS inoperability of a structure, system, or component with no redundant equipment in the same system operable constitutes an event that could have prevented the fulfillment of a safety function.
This event is also being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as operation prohibited by the plant's TSs since the as-found condition of the drain pipe clearly existed for longer than the Completion Times provide in TS 3.6.4.1, Secondary Containment.
Event Description
On April 20, 2014, at approximately 0030 Eastern Daylight Time (EDT) during operator rounds, the Reactor Building Auxiliary Operator (AO) identified pooled water on the floor on the 80-foot elevation of the west end of the Unit 2 Reactor Building. Upon further investigation, a through-wall leak in the Unit 2 Reactor Building 8-inch roof drain pipe was identified. The leak was characterized as approximately 1/4 inch in diameter and having a section of approximately 2 inches by 2 feet that was bubbled up and seeping water. At approximately 0215 EDT the leak was determined to exceed the allowable leakage margin of the Secondary Containment pressure boundary, which resulted in Secondary Containment being considered inoperable per Technical Specifications. This condition was corrected by applying a fiber wrap patch repair at approximately 0345 EDT on April 20, 2014 (i.e., approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, 15 minutes from initial discovery of the pooled water).
Causal Factors The direct cause of this event is corrosion on the Unit 2 Reactor Building roof drain pipe. The root cause of this event is that the Reactor Building roof drain pipe's equipment reliability classification was not appropriate. The classification allowed multiple opportunities to address wall thinning to be missed.
A contributing cause to this event was that the preventive maintenance (PM) inspection relied on visual inspection of the outside of the pipe. Since the exterior of the pipe is painted, corrosion is most likely to occur on the interior of the pipe. This allowed the wall thinning on the inside of the pipe to go unmonitored and degrade to the point of through-wall leaks exceeding the allowable leakage margin of the Secondary Containment pressure boundary.
Corrective Actions
Any changes to the corrective actions noted below will be made in accordance with the site's corrective action program.
The following corrective actions have been completed.
A patch was placed over the exposed region to seal the leak area.
The Unit 1 and Unit 2 Reactor Building roof drain piping was walked down by Operations during a rainstorm and no additional leakage was noted.
The methodology for inspections of the Reactor Building roof drain piping was revised to require assessments of the internal condition of the pipe.
The following corrective action is planned.
Replace the Unit 1 and Unit 2 Reactor Building roof drain piping.
The following corrective action to prevent recurrence (CAPR) is planned.
Revise the equipment reliability classification of the Reactor Building roof drain piping to Important.
Safety Analysis
There was no actual safety consequence associated with this event and the potential safety significance of this event is minimal. The principal functions of Secondary Containment are to minimize ground level release of airborne radioactive materials and to provide the means for a filtered and controlled elevated release of the Reactor Building atmosphere if an accident should occur. The safety function of Secondary Containment is to limit the release of radioactivity to the environs after an accident so that the resulting exposures are kept to a practical minimum and are within 10 CFR 50.67 and 10 CFR 100 values. At the time of discovery of this event, Secondary Containment negative pressure was maintained by normal building ventilation. This indicates that the capability of Secondary Containment was not significantly impacted by the as-found condition of the Reactor Building roof drain piping. In addition, OPT-1 5.4, Secondary Containment Integrity, which verifies the ability to maintain >/= 0.25 inch of vacuum in Secondary Containment, was performed satisfactorily on May 1, 2013.
Previous Similar Events
A review of LERs for the past three years did not identify any previous similar occurrences that were reported, however a review of corrective action program condition reports (CR) for the past three years identified the following previous similar occurrences.
CR 597004, dated March 22, 2013, identified two pin hole through-wall leaks on the Unit 2 Reactor Building 8-inch roof drain line.
CR 573214, dated November 12, 2012, identified a leak in the Unit 2 Turbine Building roof drain. While this did not impact Secondary Containment, the drain pipe is the same material, the same age, and in the same environment as the Rector Building roof drain piping.
CR 543203, dated June 15, 2012, identified holes in the Reactor Building 4-inch and 8-inch roof drain lines. The resulting quick cause evaluation determined the most likely cause to be corrosion of the carbon steel piping. Actions to correct the issue included patching the hole and initiating a long term asset management (LTAM) item for replacement of Reactor Building roof piping.
As discussed above, the root cause of this event is that the Reactor Building roof drain pipe's equipment reliability classification was not appropriate. Given the inappropriate classification, no actions to prevent recurrence were established for the above conditions. However, these conditions constitute missed opportunities and the cause analysis for this event reviewed them as input into the development of the root cause and corrective actions.
Commitments
No regulatory commitments are contained in this report.