05000325/LER-2011-001, For Brunswick, Unit 1, Regarding Loss of Control Room Emergency Ventilation

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For Brunswick, Unit 1, Regarding Loss of Control Room Emergency Ventilation
ML11165A222
Person / Time
Site: Brunswick Duke Energy icon.png
Issue date: 06/02/2011
From: Frisco J
Progress Energy Carolinas
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
BSEP 11-0058 LER 11-001-00
Download: ML11165A222 (6)


LER-2011-001, For Brunswick, Unit 1, Regarding Loss of Control Room Emergency Ventilation
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
3252011001R00 - NRC Website

text

Progress Energy June 2.2011 SERIAL: BSEP 11-0058 10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Brunswick Steam Electric Plant, Unit No. 1 Renewed Facility Operating License No. DPR-71 Docket Nos. 50-325 Licensee Event Report 1-2011-001 Ladies and Gentlemen:

In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Carolina Power

& Light Company, now doing business as Progress Energy Carolinas, 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.

Please refer any questions regarding this submittal to Mr. Lee Grzeck, Acting Supervisor -

Licensing/Regulatory Programs, at (910) 457-2487.

Sincerely, Joseph M. Frisco, Jr.

Plant General Manager Brunswick Steam Electric Plant LJG/ljg

Enclosure:

Licensee Event Report Progress Energy Carolinas, Inc.

Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461

ýe' 09-

Document Control Desk BSEP 11-0058 / Page 2 cc (with enclosure):

U. S. Nuclear Regulatory Commission, Region II ATTN: Mr. Victor M. McCree, Regional Administrator 245 Peachtree Center Ave. N.E., Suite 1200 Atlanta, GA 30303-1257 U. S. Nuclear Regulatory Commission ATTN: Mr. Philip B. O'Bryan, NRC Senior Resident Inspector 8470 River Road Southport, NC 28461-8869 U. S. Nuclear Regulatory Commission (Electronic Copy Only)

ATTN: Mrs. Farideh E. Saba (Mail Stop OWFN 8G9A) 11555 Rockville Pike Rockville, MD 20852-2738 Chair - North Carolina Utilities Commission P.O. Box 29510 Raleigh, NC 27626-0510

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, 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 1 05000325 1 of4
4. TITLE Loss of Control Room Emergency Ventilation
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIALu REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO.

MN FACILITY NAME DOCKET NUMBER 04 07 2011 2011 - 001 - 00 06 02 2011

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)

[I 50.73(a)(2)(i)(C)

[I 50.73(a)(2)(vii)

[1 20.2201(d)

El 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

F1 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

[] 50.73(a)(2)(viii)(B)

El 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)

[I 50.36(c)(1)(ii)(A)

El 50.73(a)(2)(iv)(A) 0l 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

[: 50.36(c)(2)

[I 50.73(a)(2)(v)(A)

[l 73.71(a)(4) 100 El 20.2203(a)(2)(iv)

E] 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71(a)(5)

El 20.2203(a)(2)(v)

[: 50.73(a)(2)(i)(A)

[I 50.73(a)(2)(v)(C)

C] OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B) 2 50.73(a)(2)(v)(D)

Specify in Abstract below or I_

I in The breaker, including the solid state trip unit, was removed and sent to Progress Energy's Crystal River plant breaker shop for testing, to the extent possible, and analysis. There was no evidence of a fault, and the trip unit was found to be operating within specifications during secondary current injection. No problems occurred during actual trip testing that would cause a spurious trip. The solid state trip unit was then sent to Progress Energy's Harris Environmental and Energy (HE&E) Center.. No problems were noted in the visual examination, including checks of the solder connections and inspection of the transistors for corrosion.

Discreet component checks were performed on all diodes and transistors with no failures noted. The trip unit was then sent to ABB (i.e., the original equipment manufacturer) for additional testing. The trip unit passed the secondary current injection test and the silicon control rectifier (SCR) leakage was verified to be acceptable. ABB confirmed that there have been no design changes in the trip units between 1992 and 2010. ABB could not find any problem with the trip unit. No spurious trips occurred during any of this testing and no problems related to a spurious trip were found.

Based on the evidence and analysis performed in this investigation, the spurious trip of the E-7 main breaker is attributed to a malfunction of the new solid state trip unit. However, this malfunction could not be duplicated during testing and no specific root cause could be determined.

The BSEP breaker in question is an ABB K-3000S model; which is widely used throughout the industry.

A review of external Operating Experience (OE) identified other spurious trips of this model breaker. The cause of a number of these breaker trips was attributed to the trip unit, however, testing and analysis could not ultimately identify a problem with the trip unit. Thus, spurious trips with an unknown cause attributed to the trip unit have been known to occur. The typical industry corrective action for solid state trip unit failures with undetermined causes is replacement of the individual unit.

The BSEP breaker (i.e., with its original trip unit) which had been removed from E-7 during B220R1 was reinstalled on April 8, 2011, and the substation reenergized. No subsequent problems occurred with the breaker.

Event Cause

The direct cause of the E-7 breaker trip event was a spurious actuation of the solid state trip unit. No problems could be found in the post-event testing or during repeat of the loss of offsite power/loss of coolant accident (LOOP/LOCA) test. Therefore, the root cause of this event could not be determined.

Safety Assessment

The safety significance of this event is considered minimal. The condition existed for approximately one hour and 51 minutes, and plant staff took immediate action to return the equipment to service.

Corrective Actions

The following corrective actions will be taken.

" The E-7 breaker was replaced and the substation reenergized. This action is complete.

" The tripped breaker that was removed will be refurbished, which will include replacement of the trip unit, prior to reuse. This action is currently scheduled to be completed by October 20, 2011.

Previous Similar Events

A review of LERs and corrective action program nuclear condition reports (NCRs) for the past three years identified the following similar previous occurrence.

NCR 350664, dated August 16, 2009, identified a similar failure where the feeder breaker to lighting panel IA tripped and no problem could be found. The breaker was reinstalled and has not had an additional trip. The trip unit was later replaced on May 11, 2010. The old trip unit was inspected and corrosion was observed on transistors. This event could not have reasonably been expected to prevent the condition reported in this LER. (Note that for the E-7 breaker trip identified in this LER, the new solid state trip unit that was installed on the refurbished breaker was part of an extent of condition action in response to the transistor corrosion issue identified in NCR 350664).

LER 1-2009-001, dated March 22, 2009, reports a loss of control room emergency ventilation (CREV) and air conditioning systems. The direct cause of the loss of control air to the control room ventilation system was blockage of air flow through the Control Building instrument air dryer, due to freezing of condensate within the cooling coil. This event could not have reasonably been expected to prevent the condition reported in this LER.

LER 1-2008-004, dated August 18, 2008, reports two CREV subsystems inoperable due to failure to isolate. The select cause of this event was determined to be failure to identify appropriate Preventive Maintenance (PM) routes for the CREV system components. The corrective action was to develop PM tasks for the Control Building ventilation system dampers, actuators, limit switches, and relays. This event could not have reasonably been expected to prevent the condition reported in this LER.

Commitments

No regulatory commitments are contained in this report.