05000400/LER-2010-001
| Docket Number Sequential Revmonth Day Year Year Month Day Yearnumber No. N/A 05000 | |
| Event date: | 11-10-2009 |
|---|---|
| Report date: | 01-11-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4002010001R00 - NRC Website | |
CONTINUATION REPORT
Energy Industry Identification System (EIIS) codes are identified in the text within brackets [ ].
I. DESCRIPTION OF EVENT
A past operability determination completed on November 10, 2009, concluded that on October 18, 2007, during Refueling Outage 14, a clearance rendered 1SW-271, "B" Emergency Service Water (ESW) [BI] Discharge Valve to Auxiliary Reservoir unable to remain open when opened. This resulted in the "B" ESW system being non-functional during a time when "B" ESW was required to be functional. At the time of the clearance hang, the plant was shut down in Mode 5 with loops not filled. Technical Specification 3.4.1.4.2 states two Residual Heat Removal (RHR) [BP] loops shall be operable and at least one RHR loop shall be in operation. The plant transitioned to Mode 5 with loops filled and Technical Specification 3.4.1.4.1 states at least one RHR loop shall be operable and in operation.
While in this mode "A" RHR was made inoperable for testing. For these plant modes, "B" ESW should have been in a functional status.
On October 19, 2007, at 04:19 the "B" ESW Pump was started and the Control Room Operators noticed that the Aux. Reservoir discharge valve, 1SW-271, failed to operate correctly. Because Normal Service Water (NSW) [KG] was available, the "B" ESW header was immediately realigned to be supplied by NSW and the "B" ESW Pump was secured using plant procedures. Subsequent investigation revealed that the auto open controls for 1SW-271 were disabled by clearance 153137 hung to support Engineering Change 62848. During the time that clearance 153137 checklist 7 was hung, the "B" train was the Protected Train.
"B" train RHR was inoperable from the time clearance 153137 checklist 7 was hung on breaker DP-1B-SB-33 until 1SW-271 was opened and breaker 1B35-SB-5D opened to maintain 1SW-271 open, a total time of 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 24 minutes. This was due to a non-functional "B" ESW flow path.
II. CAUSE OF THE EVENT
Inaccurate information was communicated to the clearance preparers with regards to impacted equipment associated with opening breaker DP-1B-SB-33 (Feed to Aux Transfer Panel). Work being performed was to re-wire transfer switch 43T-28SB/822. The review of impacted equipment was focused on equipment affected by the transfer switch contacts instead of equipment impacted by the breaker.
III. SAFETY SIGNIFICANCE
There were no actual significant safety consequences as a result of this condition. For the Mode that this occurred, ESW is not required to be Operable but must be functional. The safety significance is low due to the fact that NSW was supplying "B" ESW header. This condition is reportable as a condition prohibited by Technical Specifications pursuant to 10 CFR 50.73(a)(2)(i)(B) since the required number of Operable and operating RHR loops was less than that required by Technical Specifications due to "B" ESW being non-functional.
_NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER � Immediate corrective actions to this event were to open and deactivate 1SW-271 in the open position. The pump was then started and "B" ESW header was aligned to be supplied from "B" ESW Pump as a functional ESW train.
Following restoration of the "B" ESW header as a functional ESW train, clearance 153137 was lifted and breaker DP-1B-SB-33 turned on. This allowed normal operation of 1SW-271 with ESW pump starts.
Planned corrective actions to prevent recurrence are to revise procedures to alert the clearance preparers and schedulers that due to the complexity of DC power distribution circuitry, removal of DC power within Main or Auxiliary Transfer Panels, Auxiliary Relay Panels (ARPs) or Annunciator Cabinets should not be performed on equipment that is the Protected Train.
V. PREVIOUS SIMILAR EVENTS
No previous HNP events or conditions are known within the last five years where a clearance error resulted in a condition prohibited by Technical Specifications.
�