05000335/LER-2012-001
| Docketsequentia Revmonth Day Year Year Month Day Year Na Numberl Number No. | |
| Event date: | 2-10-2012 |
|---|---|
| Report date: | 04-10-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3352012001R00 - NRC Website | |
12. LICENSEE CONTACT FOR THIS LER
NAME TELEPHONE NUMBER (Include Area Code) Don Cecchett - Principal Engineer, Licensing 7 7 2-4 6 7-7 1 5 5
13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT
SYSTE MANU- REPORTABLE SYSTE COMPONE MANU- REPORTABLECAUSE COMPONENT CAUSEM FACTURE TO EPIX M NT FACTURE TO EPIX A EK DG E147 N 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR
SUBMISSION
YES (If yes, complete 15. EXPECTED SUBMISSION DATE) DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On February 1 0 , 2012, St. Lucie Unit 1 was in Mode 5 at 0% power. An electrical maintenance worker inadvertently made contact with an unprotected safety-related relay during maintenance in the immediate work area. The physical contact of the relay caused an under voltage condition on an essential bus resulting in the automatic start and loading of the 1B emergency diesel generator (EDG) . Prior to the event, the 1B EDG was inoperable but available and not required by Technical Specifications. All equipment responded as expected. The plant remained in Mode 5 with decay heat removal being supplied by the 1A shutdown cooling train without was unaffected and remained in Mode 1 at 1 0 0% power.
A root cause evaluation (RCE) concluded that plant personnel did not fully understand or question the risk significance associated with unprotected relays in the immediate work environment. Corrective actions include procedure revisions and installation of relay covers, extent of condition for safety related relays for Unit 2, review of lessons learned and training.
Description of the Event
On February 10, 2012, while replacing relay 2L/309 for HVS-1C, Unit 1 "C" Containment Fan Cooler[BK], the 27X4 under voltage (Degraded) Auxiliary Relay for the 1B2 480V Emergency Bus [JE] was inadvertently contacted. The physical contact of the 27X4 relay caused an under voltage condition which resulted in an initiation of the load shedding sequence for the 1B3 4160V Safety Related AC bus. As a result, the 1B EDG [EK] started and loaded to the 1B3 4160V bus.
Cause
A RCE concluded that plant personnel did not fully understand or question the risk significance associated with unprotected relays in the immediate work environment.
Analysis of the Event
Electrical maintenance personnel did not recognize the hazards associated with the unprotected relays within the immediate work environment. Additionally not having the manufactured covers on the relays is a legacy issue which contributed to creating a work environment conducive to contacting the relays.
Immediate corrective actions included: 1) A discussion of risk recognition associated with the event at a site leadership meeting 2) a work request to perform a walk-down inspection of relay covers for each A and B train switchgear, and the Unit 1 reactor turbine generator board (RTGB); and 3) signage posted on the doors of the 480V SWGR 1B2-2A cabinet indicating "sensitive equipment in cabinet, bus trip function inside.
Analysis of Safety Significance At the time of the event the plant was in Mode 5. Decay heat removal was being supplied by the lA shutdown cooling loop. The lA EDG was operable and 1B EDG was available. All equipment responded as expected during the start and loading of the 1B EDG.
Risk assessment during Mode 5 is performed using a qualitative assessment in accordance with the Outage Risk Assessment and Control Procedure (AP-0010526). An evaluation of plant equipment was performed following the event and no change to the Shutdown Safety Assessment occurred. Decay heat removal supplied by the lA shutdown cooling loop was never interrupted. Given there was no impact on the Shutdown Safety Assessment, there is no added risk due to this event.
This event is reportable under 10 CFR 50.73(a)(2)(iv)(A), as any event or condition that resulted in a manual or automatic activation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section. The system listed under (a)(2)(iv)(B) is (8) emergency ac electrical power systems, including: emergency diesel generators (EDGs).
Immediate Corrective Actions
1.Risk recognition associated with the event was discussed as the main topic at a site leadership meeting.
2.A work request was issued to perform a walk-down relay cover inspection, for each A and B train switchgear for the 480V 1A2,�4.16kV 1A2,� 480V 1B2,�4.16kV 1B2,�4.16kV 1A3,�6.9kV 1A1, and Unit 1 RTGB. 4.16kV lAB,�4.16kV 1B3,�6.9kv 1B1, 3.A sign was placed on the door of the 480V switch gear room (SWGR) 1B2-2A cabinet indicating "sensitive equipment in cabinet, bus trip function inside.
Corrective Actions
The corrective actions listed below are entered into the site corrective action program. Any changes to the actions will be managed under the corrective action program.
1.Revise procedures that perform maintenance/testing of relays to require upon maintenance/testing to re-install or install relay covers. If unable to install the cover, initiate an engineering change request, work request, or action request to have the relay cover procured, modified, or installed.
2.Based on a needs analysis, develop training for appropriate station personnel to incorporate the lessons learned from this event.
3.Review and document with the maintenance departments, the event and associated root cause, with emphasis on awareness of surroundings while working on or near energized equipment.
4.Perform an extent of condition on all safety related 480V, 41KV, and 480V switchgear relays that impact plant operation for Unit 1. Generate a condition report for relays identified and document the current configuration to include cover/no cover and the type of lugs installed.
5.Perform an extent of condition on all safety related 480V, 41KV, and 480V switchgear relays that impact plant operation for Unit 2. Generate a condition report for relays identified and document the current configuration to include cover/no cover and the type of lugs installed.
Similar Events A search of the corrective action database for inadvertent emergency diesel starts due to human performance for the past three years identified no similar events for St Lucie Units 1 and 2.
Failed Components
None