05000348/LER-2010-002
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 02-02-2010 |
|---|---|
| Report date: | 08-20-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3482010002R01 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
On February 2, 2010 at 1615, the Unit 1 Turbine Driven Auxiliary Feedwater (TDAFW) Pump was declared inoperable due to a high temperature identified on an electrical cable in the TDAFW Uninterruptible Power Supply (UPS) [UA]. The 1B Emergency Diesel Generator (EDG) had previously been removed from service for scheduled maintenance. As required by Technical Specification (TS) 3.8.1, "AC Sources — Operating," Required Action Statement, the Unit 1 B-Train Motor Driven Auxiliary Feedwater (MDAFW) Pump was declared inoperable at 2015 on February 2, 2010 due to the combination of its inoperable emergency power supply and inoperable redundant equipment. This resulted in two of three trains of Auxiliary Feed Water (AFW) being inoperable.
Because two out of the three trains of AFW are required to meet flow requirements for limiting design basis accidents (DBA), this represents a condition that could have prevented the fulfillment of a safety function.
TDAFW and 1B MDAFW Pumps were retumed to operable status restoring the safety function.
Further analysis of the UPS cable high temperature indicates that the TDAFW UPS function would not have been adversely affected and was therefore operable until removed from service for repairs. Based on this analysis the time of lost safety function was reduced as indicated below:
- B-Train MDAFW pump would have been inoperable at 2150 on February 2, 2010
- TDAFW and 1B MDAFW pumps were retumed to operable status at 2216 on February 2, 2010 Reporting is still necessary because repair activities removed the TDAFW UPS from service rendering two of three AFW trains inoperable for approximately 26 minutes.
Cause of Event
Evaluation of the crimped connection revealed an inadequate crimp at the connection of the lug to the end of the wire. This inadequate crimp compression did not allow the lug and wire to fasten at the proper compression to create the lowest resistance possible. This was discovered when a routine preventive maintenance (PM) thermography scan of plant equipment was scheduled during the planned outage period for EDG 1B. During this routine PM, a high temperature spot was identified in the Unit 1 TDAFW UPS at one connection.
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 1E 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.
During the short period of time the TDAFW Pump and the 1B MDAFW Pump were inoperable no work was performed on the A-Train Emergency Core Cooling System (ECCS) or the class 1 E electrical systems that could have threatened the A-Train equipment. No adverse weather conditions existed that threatened FNP's offsite power systems. No events occurred to adversely affect the operations of Unit 1 during this short period of time. At no point was the safety and health of the public challenged. The B-Train MDAFW Pump was available at all times. Therefore, the safety and health of the public was not adversely affected during the limited time the TDAFW and B-Train AFW pumps were declared inoperable.
Corrective Action The heat affected wire and lug were replaced. The Unit 1 TDAFW Pump was returned to operable status at 2216 on February 2, 2010.
Thermography scan of Unit 2 TDAFW UPS was completed with no indications of adverse wiring connections being noted.
Additional Information
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