05000348/LER-2016-001

LER-2016-001, Condition Prohibited by Technical Specifications Due to 600V Load Center Inoperable Longer than Allowed by Technical Specifications

Joseph M. Farley Nuclear Plant
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3482016001R00 - NRC Website

LER 16-001-00 for Farley, Unit 1, Regarding Condition Prohibited by Technical Specifications Due to 600V Load Center Inoperable Longer than Allowed by Technical Specifications

ML16161B272
Person / Time
Site:	Farley
Issue date:	06/09/2016
From:	Gayheart C A Southern Co, Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-16-0738 LER 16-001-00
Download: ML16161B272 (6)

Reported lessons learned are incorporated Into the licensing process and led back to Industry.

Send comments regarding burden estimate to the FOIA, Privacy end Intonation Collections Branch (1%5 F53), U.S Nuclear Regulatory Commission, Washington, DC 20555-0001, or by !Memel e-mali to Infocallecls.Resou rce 0 nro.gov, and to the Desk Officer, Office of Information and Regulatory Maks, NEOB-10202, (3150-0104), Office al Manaprnent and Budget, Washington, DC 20503. It a means used to Impose an information coliwftn does not display a currently valid OMB conkol number, the NRC may not conduct or sponsor, and a person Is not required to respond to, the Information collection.

Joseph M. Farley Nuclear Plant, Unit 1 05000- 348

A. PLANT AND SYSTEM IDENTIFICATION

Westinghouse - Pressurized Water Reactor Energy Industry Identification Codes are Identified in the text as [XX].

B. DESCRIPTION OF EVENT

On 4/12/2016 at 0312 CDT, with Unit 1 (U1) at 100 percent power and Unit 2 (U2) in Mode 5, the U2 supply breaker (ER05-2) for 1-2R 600V Load Center (LC), which can supply power for both U1 and U2, was racked out and the control power fuses removed for both U2 supply breaker and U1 supply breaker (ER02-1) to support replacing an agastat relay on ER05-2. The removal of the fuses for ER02-1 caused all of the protective relays for that breaker to be in a de-energized state. On 4/13/2016 at 0456 CDT, ER02-1 tripped open when the control power fuses were reinstalled. An attempt to reclose the breaker was unsuccessful.

Breakers ER02-1 and ER05-2 contain permissive interlocks that prevent these breakers from being closed at the same time. A contact on the ER05-2 cell switch was dirty/degraded preventing continuity between the two sides of the contact. The cell switch failed to send a signal to indicate that ER05-2 was in the racked-out position, which prevented breaker ER02-1 from reclosing.

Technical Specifications (TS) 3.8.9 Condition A was entered for Unit 1 at 0456 on 4/13/2016 when the breaker tripped open and exited at 0938 on 4/13/2016 after the contacts were cleaned on the cell switch, the control power fuses replaced and the 1-2R LC was restored to operable status.

At the time of this event Unit 2 was in Mode 5 in a refueling outage. The TS is not applicable in Mode 5.

Unit 2 had the necessary portion of the electrical power distribution subsystems operable to support the equipment required to be operable.

C. UNIT STATUS AT TIME OF EVENT

Unit 1, Mode 1, 100 percent power Unit 2, Mode 5, 0 percent power

D. CAUSE OF EVENT

The cause of the supply breaker being unable to reclose was determined to be a dirty/degraded contact in the cell switch of ER05-2 relay, preventing the interlock from reclosing.

E. REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT

If a loss of offsite power had occurred between 4/12/2016 at 0312 and 4/13/2016 at 0938, ER02-1 would have opened but would not have reclosed due to the contact on the cell switch on ER05-2, leaving the 1- 2R LC de-energized. Therefore an LER is required based on the 1-2R Load Center being inoperable for Unit 1 for longer than the TS 3.8.9 required action completion time. The breaker was in an inoperable condition for approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. This is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B).

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 Branch (1*-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by Internet wrnall to Infocollects Resource Onrc.gov, and to the Desk Officer, Office d Information and Regulatory Affairs, NEOB-10202, (3150-0104), Me of Management and Budget, Washington, DC 20503.11a means used to Impose an Information collectron 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.

Joseph M. Farley Nuclear Plant, Unit 1 05000- 348 The Farley onsite standby power source is provided from four Emergency Diesel Generators (EDG) (1-2A, 1B, 2B, and 1C). The 1C EDG has a continuous service rating of 2,850 kW and the 1-2A, 1B, 2B EDGs have ratings of 4,075 kW. EDGs 1-2A and 1C are the A-train and EDGs 1B and 2B are the B-train.

Farley also has a fifth diesel generator (2C), rated at 2,850 kW, that serves as a station blackout diesel and can be manually aligned to supply B-train power to either unit and supply power to loss-of-site-power (LOSP) loads.

During the time the 1-2R Load Center was inoperable for Unit 1, the EDGs 1-2A (A-train) and the 1B (B- train) were operable and available to support any event on Unit 1, and the 2C station blackout EDG was functional and available. For Unit 2 the 2B EDG was operable.

No other systems or components were affected by the condition described in this report. During the time of the inoperable LC no events occurred which challenged the offsite power supplies, and there was no loss of safety function. Therefore, the safety and health of the public was not adversely affected.

F. CORRECTIVE ACTION

The cell switch was cycled which cleaned the contacts, allowing ER02-1 to close. The cell switch function which failed is electrically bypassed when ER05-2 is racked-In. Post maintenance testing with ER05-2 in the racked-in position verified Operability of ER02-1. Administrative controls are in place to declare ER02- 1 inoperable when ER05-2 is racked out until the interlock is verified or ER05-2 cell switch is replaced.

The ER05-2 cell switch is scheduled for replacement in the next Unit 2 Refueling Outage. A preventive maintenance task is being developed for more frequent replacement of this component and other similar breakers.

Failed Components:

Low-Voltage Power System [EC], Westinghouse Other system affected:

None Commitment Information:

None

Previous Similar Events:

None