05000389/LER-2012-003, Regarding Inadvertent Trip of 2B3 4.16kv Switchgear

Regarding Inadvertent Trip of 2B3 4.16kv Switchgear

ML123550021
Person / Time
Site:	Saint Lucie
Issue date:	12/06/2012
From:	Jensen J Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2012-419 LER 12-003-00
Download: ML123550021 (4)

LER-2012-003, Regarding Inadvertent Trip of 2B3 4.16kv Switchgear

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)(iv), System Actuation
3892012003R00 - NRC Website

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December 6, 2012 L-2012-419 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk WashingLor,, D.C. 20555 Re:

St. Lucie Unit 2 Docket Nos 50-389 Reportable Event: 2012-003 Date of Event: October 7, 2012 Inadvertent Trip of 2B3 4.16kv Switchgear The attached Licensee Event Report 2012-003 is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Respect ly, St. Lucie Plant JJ/dlc Attachment Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/201" (10-2010)

Estimated burden per response to comply with this mandatory collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records and FOIA/Privacy Service Branch (T-5 F52),

LICENSEE EVENT REPORT (LER)

U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of

13. PAGE St. Lucie Unit 2 05000389 1 OF 3

4. TITLE Inadvertent Trip of 2B3 4.16kv Switchgear

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

(

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV IIN I

DAY YEAR IFACILITY NAME DOCKETNUMBER YER

,EA 0 'M 1

,O MONTH D

Y St.

Lucie Unit 2 05000389 10 7

20 1 2 2012 -

003 00 -

12 6

12 naFACLITYNAME DOCKETNUMBER I

AILT NAE aOCETNUME

9. OPERATING MODE

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

[1 20.2201(b)

El 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 6 El 20.2201(d)

EJ 20.2203(a)(3)(ii)

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

F1 50.73(a)(2)(viii)(A)

10. POWER LEVEL El] 20.2203(a)(1)

[I 20.2203(a)(4)

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

[I 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)

El 20.2203(a)(2)(ii) 0l 50.36(c)(1)(ii)(A)

ED 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x) 0%

El 20.2203(a)(2)(iii)

El 50.36(c)(2)

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

E] 73.71(a)(4)

12. LICENSEE CONTACT FOR THIS LER NAME TELEPHONE NUMBER (Include Area Code)

Don Cecchett - Licensing Engineer 1

772-467-7155MANU-REPORTABLE III

CAUSE

SYSTER O

NT A

EPORTABLE

CAUSE

COMPONENT FACTURER TO EPIX CAS SYTEICMONENT T

A EK NA NA NO

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATEBISO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On October 7, 2012, while in a defueled condition, a differential current lockout occurred on the St Lucie Unit 2 2B3 4.16kV essential bus, causing the bus to de-energize.

At the time of the event, the 2B emergency diesel generator (EDG) was loaded to the essential bus.

Due to the differential current lockout, all bus loads were lost and the 2B EDG output breaker feeding the essential bus opened.

The 2B EDG transferred to emergency mode and the 2A EDG remained operable and in standby.

This event is reportable pursuant to 10CFRSO.73(a)2)(iv)(A).

An investigation concluded the apparent cause was accidental shorting of the differential relay terminals while attempting to rack in the 2B component cooling water (CCW) breaker. Immediate corrective actions included systems checks and restoring the power to the 2B3 4.16kV essential bus.

The 2B3 bus differential and lockout relays were tested satisfactory and no indications of equipment failure were identified.

Corrective actions included a needs analysis to incorporate changes to training based on the lessons learned.

This event had no effect on the health and safety of the public.

NCR FORM 366 (10-2010)

Description of the Event On October 7,

2012, while in a defueled condition, a differential current lockout occurred on the St Lucie Unit 2 2B3 4.16kV essential bus, causing the bus to de-energize [JE].

At the time of the event, the 2B emergency diesel generator (EDG) was loaded to the essential bus.

Due to the differential current lockout, all bus loads were lost and the 2B EDG output breaker feeding the essential bus opened.

The 2B EDG transferred to emergency mode and the 2A EDG remained operable and in standby.

Cause of the Event

An apparent cause evaluation concluded that plant personnel did not adequately assess the risk significance associated with exposed differential relay terminals in the immediate work environment.

Analysis of the Event

The cause of the 4.16kV 2B3 essential bus inadvertent de-energization was due to the accidental shorting out of the differential relay terminals while attempting to rack in the 2B component cooling water (CCW) breaker.

An investigation concluded there was no equipment malfunction that led to the de-energization of the 2B3 4.16kV essential bus.

The 2B3 essential bus and the differential and lockout relays were tested satisfactorily with no anomalies and no indications of equipment failure.

Had a detailed risk assessment of the immediate work area been performed, additional precautions could have been implemented.

Immediate corrective actions performed included systems checks and power restoration to the 2B3 4.16kV essential bus.

Analysis of Safety Significance At the time of the event the plant was defueled and decay heat removal was being supplied by the 2A fuel pool cooling train.

All equipment responded as expected.

The actuation signal was valid and the EDG responded appropriately for plant conditions.

The fact the EDG was unable to close on the essential bus because of the differential lockout was the expected response for the system.

This event is reportable under 10 CFR 50.73(a) (2) (iv)

(A),

as any event or condition that resulted in a manual or automatic activation of any of the systems listed in paragraph (a) (2) (iv)

(B) of this section.

The system listed under (a) (2) (iv)

(B) is (8) emergency ac electrical power systems, including EDGs.

Risk assessments are performed daily during outages using a qualitative assessment in accordance with the "Outage Risk Assessment and Control Procedure" (AP-0010526).

An evaluation of plant equipment was performed following the event and no change to the shutdown safety assessment (SSA) occurred.

Given there was no impact on the SSA, there is no added risk due to this event.

Corrective Actions

The corrective actions listed have been entered into the site corrective action program (CAP).

Any changes to the actions below will be processed in accordance with the CAP.

1. Perform system checks and restore power to the 2B3 4.16kV essential bus.

2.

Perform a needs analysis and incorporate recommended changes to training based on lessons learned from this event.

Repeat Events A search of the corrective action database for inadvertent emergency diesel starts due to human performance for the past two years identified no repeat events for St Lucie Units 1 and 2.

The review did identify two similar industry events that have occurred due to human performance issues. The first event involved Next Era's Seabrook Station where a 4.16kV essential bus was lost as a result of less than adequate peer checking and questioning attitude. The second event involved Saint Lucie Unit 1 during replacement a relay in a 480V safety related switchgear compartment. Electrical maintenance personnel accidentally made contact with an auxiliary under voltage (UV) relay resulting in the initiation of a load shedding sequence for the 1B3 4.16kV essential bus and the emergency start of the lB EDG.

The root cause was inadequate work practices and human performance behaviors.

Failed Components None