05000364/LER-2011-001
| Joseph M Farley Nuclear Plant - Unit 2 | |
| Event date: | 07-07-2011 |
|---|---|
| Report date: | 09-22-2011 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3642011001R00 - NRC Website | |
Westinghouse — Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
On July 30, 2011 at 23:04 while at 100% power, the Unit 2 Turbine Driven Auxiliary Feedwater Pump (TDAFWP) [BA] automatically tripped on overspeed during surveillance testing. Through subsequent investigation it was determined that Unit 2 was not in compliance with Technical Specification (TS) 3.7.5 in that the Unit 2 TDAFWP had been rendered inoperable on July 7, 2011 at approximately 10:44 as a result of an inappropriately planned maintenance activity to correct an apparent wiring discrepancy that impacted turbine governor speed control. Electrical leads were incorrectly identified as spares and erroneously removed per plant drawings that contained unknown legacy errors. The work was planned in error as a minor maintenance activity and as such TDAFWP was unknown to be inoperable; a second train of Auxiliary Feedwater (AFW) was made inoperable to support scheduled maintenance of Emergency Diesel Generators (EDG) [EK] and a Motor Driven Auxiliary Feedwater Pump (MDAFWP) as indicated below:
t 1-2A EDG 2. 1-2A EDG 3. 2B EDG 4. 2B MDAFWP RAS Entered 7/7/11 at 22:52 RAS Entered 7/8/11 at 20:40 RAS Entered 7/18/11 at 11:36 RAS Entered 7/28/11 at 04:30 RAS Exited 7/8/11 at 05:16 RAS Exited 7/13/11 at 04:17 RAS Exited 7/19/11 at 13:29 RAS Exited 7/28/11 at 21:30 This resulted in two of three trains of AFW being inoperable. This represents a condition that could have prevented the fulfillment of a safety function because two out of the three trains of AFW are required to meet flow requirements for limiting design basis accidents (DBA).
The Unit 2 TDAFWP wiring was restored to the correct configuration and subsequent surveillance testing was completed satisfactory on August 1, 2011 at 03:40.
Cause of Event
This event occurred due to a legacy drawing error that caused a difference between the actual field wiring of the plant and as-built drawings. The field wiring of the plant was changed to match the as- built drawings that were flawed. This made the Unit 2 TDAFWP inoperable. Additional causes resulted from the improper use and control of work under Minor Maintenance, and Engineering incorrectly evaluating the as-built field configuration.
Safety Assessment 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) that serves as a station blackout diesel which can be manually aligned to supply B-Train power to either unit and power Loss of Site Power (LOSP) loads. The diesel generator 2C can provide backup power to the buses supplied by 1B EDG. Procedures are in place and operators are trained on starting the 2C diesel generator for alignment to the B-Train emergency buses.
The AFW System consists of two motor driven AFW pumps and one steam turbine driven pump configured into three trains. The pumps are equipped with recirculation lines to prevent pump operation against a closed system. Each motor driven AFW pump is powered from an independent Class 1 E power supply and feeds all steam generators through a common header. The steam turbine driven AFW pump receives steam from two main steam lines upstream of the main steam isolation valves. The turbine driven AFW pump supplies a common header capable of feeding all steam generators via Direct Current (DC) solenoid air operated control valves actuated by the Engineered Safety Feature Actuation System (ESFAS). Thus, the requirement for diversity in motive power sources for the AFW System is met. Two of the three AFW pumps are required to ensure the flow demand for the most limiting DBAs and transients is satisfied.
With the Unit 2 TDAFWP unknown to be inoperable and an EDG out of service for more than four hours; per Technical Specification (TS) 3.8.1, "AC Sources - Operating," Required Action Statement (RAS), the train related MDAFWP would be considered inoperable due to the combination of its inoperable emergency power supply and inoperable redundant equipment (TDAFWP). However, in each instance when an EDG was removed from service for routine maintenance, the corresponding train related MDAFWP remained available. While the EDG was out of service, no work was performed on opposite train class 1 E electrical systems that could have threatened the remaining operable MDAFWP. In addition, the TDAFWP could have been operated by procedure in local manual control if necessary.
In the short time during which the B-train 2B MDAFWP was actually out of service, the A-train 2A MDAFVVP remained operable.
No adverse weather conditions threatened Farley's offsite power systems during this period of time.
No events occurred to adversely affect operations and Unit 2 remained at 100% power while the TDAFWP was inoperable. At no point was the safety and health of the public challenged.
Therefore, the safety and health of the public was not adversely affected while two of three trains of AFW were inoperable.
NRC FORM .336A 110-2010) NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION
CONTINUATION SHEET
2. DOCKET
Joseph M. Farley Nuclear Plant - Unit 2 05000 364 Corrective Action The Unit 2 TDAFWP wiring was restored to the correct configuration and subsequent surveillance testing was completed satisfactory.
The TDAFWP wiring drawings for both Unit 1 and 2 were found in error and will be corrected by October 15, 2011.
A root cause (CR 333399) was initiated and additional corrective actions were identified. These actions to reinforce performance expectations, assess training needs, and to improve processes will be tracked to closure in the corrective action system.
Additional Information
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TDAFWP Inoperable Due to Internal Flooding Concerns