05000364/LER-2010-003
| Joseph M Farley Nuclear Plant - Unit 2 | |
| Event date: | 08-05-2009 |
|---|---|
| Report date: | 07-21-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3642010003R00 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
During the period between August 5 and August 9, 2009, the Unit 2 power supply to 1-2R 600 V load center (LC) did not meet the Unit 2 portion of Technical Specification (TS) 3.8.9 "Distribution Systems — Operating." This was discovered on August 9, 2009 when during routine surveillance for on-site AC distribution, the Unit 2 4160 V supply breaker DH08-2 [EB] to 1-2R 600 V LC was found to be in the open position. The 1C emergency diesel generator (EDG) [EK] power supply to the LC was declared inoperable for Unit 2 due to the 1-2R 600 V supply breaker from Unit 2 being open.
Subsequently, the 4160 V supply breaker DH08-2 was closed. Subsequent evaluation and interpretation of limiting condition for operation (LCO) 3.8.9 resulted in the conclusion that with the 4160 V supply breaker DH08-2 open, TS 3.8.9 LCO for maintaining two trains of AC vital bus electrical power distribution subsystems operable was not met. The 1-2R 600 V LC did not meet its surveillance requirement of correct breaker position and voltage for longer than allowed by TS.
Cause of Event
The 1-2R 600 V LC was returned to service with the Unit 2 4160 V supply breaker, DH08-2, in the open position due to omission of relevant information in procedures. The 2H 4160 V bus was reenergized per operating procedure for the 4160 V AC distribution system. That procedure did not direct the closure of the 4160 V supply breaker DH08-2 directly, but instead referenced another procedure. The 4160 V supply breaker DH08-2 was not closed because LC was energized from its alternate source, which at the time was believed to be all that was required to make the LC Operable per TS and because additional work was scheduled the following week that required the LC to be on its alternate source.
A contributing factor was that the Licensee's interpretation of LCO 3.8.9 that existed at the time did not include a requirement to have both 4160 V supply breakers to the 1-2R LC closed.
Based on this, the 1-2R 600 V LC was left aligned to its alternate power supply. It was recognized that the 4160 V supply breaker DH08-2 would be left open and, after maintenance was complete, procedures would return the system to a normal lineup. It was not recognized that with the 4160 V supply breaker DH08-2 open, the 1-2R 600 V LC was not Operable in accordance with LCO 3.8.9.
Safety Assessment This event had no adverse effect on the safety and health of the public.
The Farley onsite standby power source is provided from four EDGs (1-2A, 1B, 2B, and 1C). The continuous service rating of 1C EDG is 2,850 kW and 4,075 kW for EDGs 1-2A, 1B, and 2B. EDG 1-2A and 1-C are A-Train and EDGs 1B and 2B are 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 power loss-of-site-power (LOSP) loads.
During the time that EDG 1C was inoperable (August 5 to August 9, 2009) for Unit 2, the EDG 1-2A and EDG 2B were operable and available to support any event on Unit 2, and the diesel generator 2C was available. During the time that 1C EDG was inoperable for Unit 2, no events occurred which challenged the off-site power supplies. No safety system functional failures occurred. The 1 2R 600 V LC was aligned to its Unit 1 supply and the bus was energized to its proper voltage.
Therefore, the safety and health of the public was not adversely affected.
Corrective Action 1.The 4160 V supply breaker DH08-2 was reclosed on August 9, 2009.
2. Procedures were revised such that the appropriate operability determination will be made for the 1-2R 600 V LC and to contain guidance to reclose the 4160 V supply breaker DH08-2, as well as explaining the LCO consequences of not closing the supply breakers to the 1-2R 600 V LC.
Additional Information
This LER is being submitted more than sixty-days after the event date due to the initial classification of this event by the licensee as non-reportable. The power-seeking function for the 1-2R 600 V LC was considered by the licensee to be a function associated with EDG 1C since the LC supplies the auxiliary loads for the EDG, thus the event was not reportable. Subsequently, the NRC determined that the power-seeking function was a part of the Electrical Distribution System (LCO 3.8.9). The NRC formalized their position in Inspection Report 2009-005.
Previous Similar Event: None.