05000387/LER-2007-001
| Asusquehanna Steam Electric Station - Unit 1 | |
| Event date: | 05-24-2007 |
|---|---|
| Report date: | 07-19-2007 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3872007001R00 - NRC Website | |
EVENT DESCRIPTION
At 1125 on May 24, 2007, the 'C' Emergency Service Water (ESW; EIIS Code: BI) pump automatically started when the `E' Diesel Generator (DG; EIIS Code EK) was manually started to perform testing following in Mode 1 at 100% power. No structures, systems, or components were inoperable at the beginning of the event that contributed to the event.
Susquehanna has a total of five DGs that are common to Units 1 and 2. The 'A' through 'D' DGs are normally aligned for standby service, and any aligned DG can supply its respective engineered safeguards bus in both units. The fifth DG ('E' DG) can be aligned as a replacement for any one of the four normally aligned DGs to facilitate maintenance. No ESW pump automatic start signals are generated during operation of the 'E' DG in an unaligned condition. With the 'E' DG aligned as a substitute for one of the normally aligned DGs, a start signal for the associated ESW pump would be generated following a start of the `E' DG. During the event, the `E' DG was aligned as a substitute for the 'C' DG. With the plant aligned in this manner, the 'C' ESW pump would be expected to start (if not already running) following a start of the 'E' DG, and the pump start was therefore in accordance with plant design. All plant equipment operated as designed.
On the day prior to the event, the 'A' and 'B' ESW pumps were placed in service to support surveillance testing of the 'A' DG. These pumps remained in service to support the testing of the 'E' DG that was being performed prior to substituting the 'E' DG for the 'C' DG. The `E' DG testing was performed with the DG unaligned (i.e., not substituting for any of the normal DGs). Following completion of the unaligned testing, a plant operator (licensed, utility) was assigned to align the `E' DG as a substitute for the 'C' DG in anticipation of removing the 'C' DG from service for maintenance. The operator worked through the procedure steps for an aligned operability test of the 'E' DG using the appropriate surveillance procedure. The prerequisites in the procedure require ESW be aligned and include a note that indicates the associated ESW pump is preferred due to the pump receiving a start signal. This note was overlooked by the operator when he verified and checked the procedure step indicating adequate ESW flow to support the 'E' DG test. The operator was in a mindset that proper ESW flow existed to support the test since the same pumps (`A' and 'B') supported the previous unaligned `E' DG runs. An informal discussion between the operator and a supporting operator (non licensed, utility) was conducted in lieu of a formal pre-job brief, and consequently, the pre-job brief database that provided a caution for starting the associated ESW pump was not used. A peer check was not performed for the `E' DG start contrary to the Operations standard for starting large equipment and management oversight for the activity was not adequate.
Following the 'C' ESW pump start, the 'A' ESW pump was shutdown and the 'C' ESW pump was verified to be operating normally.
CAUSE OF EVENT
The start of the 'C' ESW pump is attributed to a human performance error in that a procedure prerequisite for ensuring proper ESW alignment was marked complete but not implemented as intended. Causal factors included failure to perform a formal pre-job brief, failure to utilize peer checking, and less than adequate management oversight in that management expectations for pre-job briefs and peer checking were not enforced.
ANALYSIS / SAFETY SIGNIFICANCE
This event is reportable as an event that resulted in an unplanned automatic actuation of an ESW system per 10 CFR 50.73(a)(2)(iv)(A).
There were no actual or potential consequences as a result of the automatic start of the 'C' ESW pump. The event does not represent a degraded condition but rather an unexpected start of a pump designed to automatically start.
Although the pump started as designed, the start was not anticipated by Operations. The 'A' and 'B' ESW pumps were already running and provided the necessary cooling to the `E' DG that had just started. The preferred pump alignment is to have one pump in each loop running to ensure optimal performance relative to the pump curve, but the system design provides a sufficient flow path to support having all four ESW pumps operating. The significance of the event is limited to an unnecessary actuation of a system provided to mitigate the consequences of a significant event.
CORRECTIVE ACTIONS
1. The operators involved in the event have been coached and counseled.
2. A communication to on-shift Operations personnel was issued that discussed the event and reinforced expectations for procedure compliance.
3. Training will be provided to on-shift and work control center Operations personnel regarding this event and will include emphasis on the human performance and supervisory oversight expectations that were not met during the event.
ADDITIONAL INFORMATION
Past Similar Events: LER 2004-001-00, Docket No. 387/License No. NPF-14 Failed Component: None