05000272/LER-2011-001
| Salem Generating Station - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| 2722011001R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
Westinghouse — Pressurized Water Reactor (PWR/4) Service Water System/Strainer {BUSTR } * Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: January 17, 2011 Discovery Date: January 17, 2011
CONDITIONS PRIOR TO OCCURRENCE
Salem Unit 1 was in Operational Mode 1 at 100% reactor power.
DESCRIPTION OF OCCURRENCE
In 2006, the No. 12 SW strainer stanchion had been inspected and corrosion was found at the base. A work order was initiated to repair the stanchion but had not been worked as of December 9, 2010.
On December 9, 2010 during a walkdown of the No. 1 Service Water Intake Structure (SWIS) bay, severe corrosion at the base of a six inch stanchion (pipe) that supports the power supply cable for the No. 12 Service Water (SW) strainer motor was observed.
An engineering evaluation concluded that the as-found condition of the support would not have been capable of withstanding seismic loads. The No. 12 SW pump was declared inoperable on December 9, 2010 due to corrosion of the SW strainer {BUSTR} power supply cable support stanchion. The SW strainer power supply cable support stanchion was repaired and the No. 12 SW pump returned to service on December 16, 2010.
Technical Specification (TS) 3.7.4.1 states that at least two independent service water loops shall be OPERABLE in Modes 1 through 4. With only one service water loop OPERABLE, restore at least two loops to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. One SW loop is defined as at least two of three SW pumps and associated strainers in a SW bay OPERABLE. With two SW pumps OPERABLE, a third SW pump in the associated bay can be removed from service for an unlimited time.
An engineering review was performed of the SW pump availability for past three years [per NUREG 1022 guidance], assuming the power supply cable support stanchion was unable to perform its function in a seismic event one year after the 2006 identification and repair. The engineering review, completed on January 17, 2011, identified eight instances when a SW pump other than the No. 12 SW pump had been inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The inoperability of two SW pumps resulted in an inoperable SW loop for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Therefore, this report is being made in accordance with 10CFR50.73 (a)(2)(i)(B), "any operation ... prohibited by the plant's Technical Specification.
CAUSE OF OCCURRENCE
The cause of this occurrence is attributed to untimely repairs to the corroded power supply cable stanchion. In 2006, the No. 12 SW strainer power supply cable stanchion had been inspected and corrosion was found at the base. Pipe wall measurements were acceptable and although it was noted there was little margin remaining, the stanchion was cleaned to base metal and protectively recoated. A work order was initiated to repair the stanchion but had not been worked as of December 9, 2010.
PREVIOUS OCCURRENCES
A review of LERs for Salem Units 1 and 2 back to 2006 did not identify any previous similar occurrences.
SAFETY CONSEQUENCES AND IMPLICATIONS
There was no actual safety consequences associated with this event. This condition only impacted the No.12 SW pump during a seismic event. There was no impact to the No. 12 SW pump operation during a loss of coolant accident (LOCA), loss of offsite power (LOOP) or a LOCA/LOOP. The potential loss of an additional service water pump during a seismic event was assessed for its impact.
The most limiting condition was determined to be a seismic event with loss of offsite power and a failure of either the "A" or "B" Emergency Diesel Generators which would result in one SW pump in service.
Operations procedures provide sufficient guidance for subsequent actions to mitigate any adverse consequences of such an event. During the eight instances identified where the SW Technical Specification LCO was exceeded, all diesels were available to support SW pump operation.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in NEI 99- 02, Regulatory Assessment Performance Indicator Guidelines, did not occur. There was no condition that alone could have prevented the fulfillment of a safety function of a system needed to mitigate the consequences of an accident.
CORRECTIVE ACTIONS
1. The No. 12 SW power supply cable support stanchion was repaired and returned to service.
2. All Salem Unit 1 and 2 SWIS SW Strainer stanchions were inspected and found to be operable.
3. An evaluation is in progress; any additional corrective actions associated with this event will be tracked in the PSEG Corrective Action Program.
COMMITMENTS
No commitments are made in this LER.