05000324/LER-2016-002-01, For Brunswick Steam Electric Plant Unit 1 Regarding Emergency Diesel Generator 3 Inoperable Due to Failure to Auto-Start

For Brunswick Steam Electric Plant Unit 1 Regarding Emergency Diesel Generator 3 Inoperable Due to Failure to Auto-Start

ML16230A236
Person / Time
Site:	Brunswick
Issue date:	08/08/2016
From:	William Gideon Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 16-002-01
Download: ML16230A236 (9)

LER-2016-002, For Brunswick Steam Electric Plant Unit 1 Regarding Emergency Diesel Generator 3 Inoperable Due to Failure to Auto-Start

Event date:
Report date:
Reporting criterion:	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)(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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
3242016002R01 - NRC Website

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~ ENERGY AUG 0 8'2016 Serial: BSEP 16-0054 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facili.ty Operating License Nos. DPR-71 and DPR-62 Docket No. 50-325 and 50-324

• Licensee Event Report 1-2016-002, Revision 1 William R. Gideon Vice President Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461 o: 910.457.3698 10 CFR 50.73 Reference: Brunswick Licensee Event Report 1-2016-002, dated May 2, *2016 (ADAMS Accession Number ML16132A076)

In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Duke Energy Progress, Inc., submits the enclosed Revision 1 to Licensee Event Report (LER) 1-2016-002.

This revision is the result of an update to the supporting cause evaluation.

This document contains no regulatory commitments.

Please refer any questions regarding this submittal to Mr. Lee Grzeck, Manager - Regulatory Affairs, at (910) 457-2487.

William R. Gideon MAT/mat

Enclosure:

Licensee Event Report

U.S. Nuclear Regulatory Commission Page 2 of 2 cc (with enclosure):

U.S. Nuclear Regulatory Commission, Region II ATTN: Ms. Catherine Haney, 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 (Electronic Copy Only) 4325 Mail Service Center Raleigh, NC 27699-4300 swatson@ncuc.net

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 (06-2016)

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 />.

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Reported lessons learned are incorporated into the licensing process and fed back to industry.

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LICENSEE EVENT REPORT (LER)

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

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Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail (See Page 2 for required number of digits/characters for each block) to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an information ccllection does not display a currently valid OMB central httg://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3D number, the NRG 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 OF 7

4. TITLE Emergency Diesel Generator 3 Inoperable Due to Failure to Auto-Start

5. EVENT DATE

6. LEA NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER.

MONTH DAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR BSEP, Unit2 05000324 FACILITY NAME DOCKET NUMBER 03 04 2016 2016 - 002

- 01 08 08 2016 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

D 20.2201 Cb)

D 20.2203(a)C3Hil D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201 (dl D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 5 D 20.2203(a)c1 l D 20.2203(a)(4l D so.13(a)(2)(iiil D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1 )(i)(A)

[8J 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2)(iil D 50.36(c)(1)(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11(a)(4l D 20.2203(a)(2)(iiil D so.36(c)(2)

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

D 13.11 (a)(s)

D 20.2203(a)(2)(iv)

D so.46(a)(3)(iil D 50.73(a)(2)(v)(C)

D 13.77(a)(1) 000 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

[8J.50.73(a)(2)(v)(D)

D 13.11(a)(2)(i)

D 20.2203(a)(2)(vi)

[8J 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii).

D 13.77(a)(2)(iil D 50.73(a)(2)(i)(C)

D OTHER Specify in Abstract below or in On February 8, 2016, at 2211 Eastern Standard Time (EST), Unit 2 would have been required to be in Mode 3 in accordance with TS 3.8.1, Required Action H.1, for one offsite circuit inoperable and one EOG inoperable (i.e., TS 3.8.1, Condition F).

On February 12, 2016, at 2357 EST, Unit 1 entered Mode 2 from Mode 4. This constituted a violation of Limiting Condition for Operation (LCO) 3.0.4.

On February 20, 2016, at 1157 EST, Unit 1 would have been required to be in Mode 3 in accordance with TS 3.8.1, Required Action H.1, for a single EOG inoperable (i.e., TS 3.8.1, Condition D).

On February 21, 2016, at 0806 EST, Unit 1 and Unit 2 would have been required to be in Mode 3 in accordance with TS 3.8.1, Required Action H.1, for two EDGs inoperable (i.e., TS 3.8.1, Condition G).

01 On March 3, 2016, at 2108 EST, Unit 2 would have been required to be in Mode 2 in accordance with LCO 3.0.3, per TS 3.8.1, Condition I, (i.e., one or more offsite circuits and two or more Diesel Generators (DGs) inoperable).

10, CFR 50. 73(a)(2)(iv)(A)

On March 3, work was ongoing to restore power to BOP bus 1 D when an error in the restoration sequence resulted in an invalid auto-start of EDGs 2 and 4 at 1332 EST. EDGs 2 and 4 responded properly to the auto-start signal and ran unloaded. Since no actual bus under voltage condition existed which required the EDGs to start, and the start was not in response to actual plant conditions satisfying the requirements for initiation, this event has been classified as an invalid actuation. Because the invalid auto-starts of EDGs 2 and 4 are directly r~lated to the events associated with this LER, the event is being reported via this LER rather than the optional 60-day telephone notification as allowed by 1 O CFR 50.73(a)(1).

Event Description

On March 2; at 1458 EST, EOG 1 was declared inoperable in support of modifications, maintenance activities, and testing. Emergency bus E1 and balance of plant (BOP) bus 1 D were deenergized in support of this work. This was a planned maintenance activity, being performed during the ongoing Unit 1 refueling outage. Due to the shared electrical distribution system at Brunswick, Unit 2 was in TS 3.8.1, Condition B (i.e., two Unit 1 offsite circuits inoperable due to one Unit 1 balance of plant circuit path to the downstream 4.16 kV emergency bus inoperable for planned maintenance and the EOG associated with l the affected downstream 4.16 kV emergency bus inoperable for planned maintenance).

• i On March 3, work was ongoing to restore power to BOP bus 1 D when an error in the restoration sequence resulted in an invalid auto-start of EDGs 2 and 4. The invalid signal mimicked undervoltage on the startup auxiliary transformer (SAT) [EA], which is not a TS required start and, per design, would have started EDGs 1, 2, 3, and 4. EOG 1 was under clearance and, as such, did not start. However, it was also expected that EOG 3 should have started. Troubleshooting activities and a thorough EOG 1 modification review were initiated. As a result, on March 4, 2016, at 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br /> EST, it was determined that continuity was lost across a dummy fuse block in the auto-start circuitry for EOG 3. This failure prevented TS required auto-actuation of EOG 3. Therefore, EOG 3 was declared inoperable. At this time, Unit 2

2. DOCKET NUMBER YEAR 05000-325 2016 -

3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.

01 entered TS 3.8.1, Condition I, (i.e., one or more offsite circuits and two or more Diesel Generators (DGs) inoperable). Required Action 1.1 directs immediate entry into LCO 3.0.3.

Duke Energy Progress, Inc., verbally requested a Notice of Enforcement Discretion (NOED) to extend the time required by LCO 3.0.3 for Unit 2 to be in Mode 2, Mode 3, and Mode 4 by 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />. The NRG verbaily approved the NOED at 1535 EST on March 4, 2016. EOG 3 was restored to operable status and LCO 3.0.3 was exited at 1834 EST after replacement of the fuse holder. This was before the original Completion Time of LCO 3.0.3 (i.e., be in Mode 2 by March 4, 2016, at 1935 EST).

As a result of the root cause evaluation of this event, the direct cause of the EOG 3 failure to auto-start was identified as a loss of continuity in the 2-DG3-FU-1-ECR Dummy Fuse at EDG 3 Emergency Control Relay (ECR) Disconnect; specifically, loose fuse clamps in the dummy fuse block/holder. Further, there is firm evidence that this condition existed since February 7, 2016, when EOG 3 successfully auto-started in response to a Unit 1 SAT lock-out condition, the details of which are discussed in Brunswick LER 1-2016-001, dated April 6, 2016. On February 7, operators observed that the auto-start indications for EOG 3 (i.e., annunciator UA-21 5-2, and lights) had cleared, without operator action. This provides indication that the loss of continuity in the dummy fuse holder occurred at that time. The unexpected clearing indicates a loss of power to the ECR relay, the same failure mechanism that prevented EOG 3 auto-start on March 3. Therefore, it is concluded that the equipment issue was present from February 7 until March 4, when the fuse holder was replaced. lnoperability of EOG 3 was determined to be from 2211 EST on February 7, when the EOG 3 was secured from the auto-start, until 1834 EST on March 4, 2016, foll<;>wing replacement of the faulty fuse holder.

A review was performed to determine instances when EDGs 1, 2, or 4 were inoperable during the period from February 7, 2016, until March 4, 2016. The following instances were identified. Note, the times provided are approximate, based on Operations Log entries.

EOG 1 February 20 at 1806 EST to March 2 at 1226 EST (i.e., 10 days, 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, 20 minutes) for planned replacement of the automatic voltage regulator and margin improvement modifications.

March 2 at 1458 EST to March 9 at 0,151 EST (i.e., 6 days, 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, 53 minutes) for, Division 1 electrical outage and DG 1 governor.modification. Note that EOG 3 was restored to operable status at 1834 EST on March 4.

EDG2 February 19 from 2025 EST to 2053 EST (i.e., 28 minutes) for barring.

February 19 from 2104 EST to February 20 at 0014 EST (i.e., 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, 1 O minutes) for surveillance testing.

EDG4 05000-325 YEAR 2016 -

SEQUENTIAL NUMBER 002 February 15 from 1235 EST to 1434 EST (i.e., 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 59* minutes) for surveillance testing:

February 18 from 2106 EST to 2140 EST (i.e., 34 minutes) for barring.

REV NO.

01 February 18 from 2154 EST to February 19 at 0119 EST (i.e., 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, 25 minutes) for surveillance testing.

During the above periods, Unit 2 was in Mode 1. Unit 1 was in Mode 1 until February 26 at 2129 when Mode 3 was entered to start the refueling outage.

Event Cause

The root cause of this event is a design vulnerability associated with relaxation of the EOG 3 fuse holder fingers which was not properly mitigated. The existing design lacks circuit continuity indication that is not mitigated by design or testing.

The direct cause for the EOG 3 failure to start was determined to be a loss of continuity through a dummy fuse in the auto-start logic circuit for EOG 3, which prevented the ECR coil from being energized and thus starting the diesel. The loss of continuity through the ECR fuse block assembly was a result of loose fuse holder fingers. ECR fuse block assembly was installed as a result of a 2011/2012 modification performed on the auto-start circuitry of each EOG. This modification installed an intermediate clearance point between the Lock Out Control Relay (LOCR) and ECR. During the 2011 engineering change process where the fuse block design was identified, the risk was identified that fuse block/clip-to-fuse electrical contact may open/fail. The risk was identified but positive measures were not put into place to mitigate the risk beyond visual verification that the brass dummy fuse was installed.

Safety Assessment

The safety significance of this event is minimal.

On March 3, 2016, BOP Bus~1D, E1, ES, and EOG 1 were inoperable due to.. ongoing maintenance (i.e.,

Unit 1 Division 1 AC outage vyindow). The planned Unit 1 maintenance acti'{,ity had been properly risk assessed prior to the beginnfng of the outage. The unplanned inoperability of EOG 3 had minimal impact on Unit 1. EOG 3/E3 are primarily associated with Unit 2 loads. A loss of power to E3 could have impacted the 1A Residual Heat Removal (RHR) pump [BO] and the 1A RHR Service Water (SW) pump [BO]. However, on March 3, Unit 1 was flooded up with the spent fuel pool gates removed. Time to boil was approximately 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br />. Per TS 3.9.7, one RHR shutdown cooling subsystem is required to be operable and in operation in Mode 5 with irradiated fuel in the Reactor Pressure Vessel (RPV) and the water level greater than or equal to 21 feet 1 O inches above the RPV flange. The primary means of shutdown cooling was B RHR with D RHR the backup. Additionally, EOG 3 could be manually started.

Based on these considerations, the event is of minimal safety significance for Unit 1.

05000-325 YEAR 2016 -

SEQUENTIAL NUMBER 002 REV NO.

01 On March 3, 2016, Unit 2 remained in Mode 1. EOG 2, EOG 4, and offsite power sources (i.e., excluding offsite power to emergency bus E1) were not affected by the EOG 1 maintenance and were operable.

Emergency buses E2, E3, and E4 continued to be powered from offsite power. As such, sufficient offsite power supplies remained available to complete their intended safety function. The Supplemental Diesel Generator (SUPP-DG), installed to support a 14-day completion time for an inoperable EOG, remained available, as well as the two permanently installed FLEX diesels. The SUPP-DG is rated at 4000 kW, 4160 VAC, and can provide power to the emergency busses in approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Each FLEX diesel is rated at 500 kW, 480 VAC, and can be connected to the emergency busse$ in less than one hour.

~xcept for the periods of time for repair activities and post-repair testing, EOG 3 was available via manual start.

A Probabilistic Risk Assessment (PRA) was performed to determine the impact of EOG 3 being inoperable from February 7 until March 4, 2016. This analysis concluded that this was of very low safety significance.

Corrective Actions

Any changes to the corrective actions and schedules noted below will be made in accordance with the site's corrective action program.

The following corrective action to prevent recurrence is planned.

A design change, for each EOG ECR fuse block, to ensure continuity is maintained or a loss of circuit continuity is detected will be installed. Installation is currently scheduled to be completed by December 31, 2017.

In addition, the following corrective actions have been completed or are planned.

EOG 3 was restored to operable status on March 4, 2016, after replacement of the degraded dummy fuse holder. The dummy fuse holders for EDGs 1, 2, and 4 will be replaced. This is currently scheduled to be completed by October 10, 2016.

Previous Similar Events

A review of LERs for the past five years identified the following previous similar occurrence.

~

A LER 1-2015-002, Revision 1, dated November 11, 2015, reported loss of safety function due to inoperability of EDGs 3 and 4. The root cause of the event was a procedural inadequacy in the commercial grade dedication process that allowed an unauthorized component modification to go unrecognized. To prevent recurrence of a similar event, procedure AD-EG-ALL-1103, "Procurement Engineering Products," was revised. Since the causes of the events were different, the actions from LER 1-2015-002 could not have reasonably been expected to prevent the condition reported in LER 1-2016-002.

Commitments

05000-325 No regulatory commitments are contained in this report. YEAR 2016 SEQUENTIAL NUMBER 002 REV NO.

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