05000397/LER-2015-004
| Columbia Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3972015004R00 - NRC Website | |
Plant Conditions
2. DOCKET
05000 397 Eslimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
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At the time of the event the plant was in Mode 5, water level was at the normal refuel flooded level with fuel pool cooling gates removed. Water Level Band was 487 - 491" and the temperature band was 80 -110 degrees F. Division 2 was providing the electrical power and supporting components required for decay heat removal and inventory control. The Division 1 Service Water System [Bl] and Diesel Generator (DG-1) [EK] were inoperable but available in preparation for Loss of Coolant (LOCA) testing of DG-1. The Division 1 4.16KV Bus 7 Switchgear (E-SM-7) [SWGR] became inoperable due to this event but it was not required for compliance with Technical Specifications 3.8.2 because the plant was in a Division 1 outage and the Division 2 E- SM-8 remained operable.
Event Description
On May 22, 2015, Maintenance electricians supporting Operations in the performance of LOCA testing of DG-1 connected three Fluke 43 meters [HZM] at the E-SM-7 cabinet for harmonic data collection. The test leads were not long enough to reach from the terminal strip to the floor, so the Flukes were duct taped to the inside of the cabinet and the test leads connected. After a pre-job brief with Operations and prior to initiating the LOCA test, the electricians checked on the meter set up and found that one of the Fluke meters had fallen to the cubicle floor and one of the test leads had become disconnected. At approximately 00:14 one of the electricians reinstalled the meter and when reconnecting the test lead inserted it into the wrong port on the Fluke. This resulted in a potential transformer (PT) phase to phase short which caused a momentary loss of bus E-SM-7. The Backup Transformer (E-TR-B) [XFMR] sensed the loss and repowered the bus. In addition DG-1 sensed the bus under-voltage condition and received an initiation signal causing it to start.
At 00:16, the Division 1 Diesel Generator was removed from service when its support Standby Service Water pump (SW-P-1A) [P] did not start. The pump failed to start due to a blown fuse [FU] caused by the short in the E-SM-7 Phase B-C Primary Under Voltage Relay, E-RLY-27/7/2 [RL Y]. The failure of SW-P-1A did not impact any other safety functions because Division 2 equipment was relied upon for safety functions at the time.
The event caused the Reactor Building [NG] ventilation [LE] to isolate, as expected. The Division 1 Standby Gas Treatment system [BH] was already running in preparation for Secondary Containment [NH] differential pressure surveillance. The blown fuse prevented restoration of Reactor Building ventilation and load-shed power to Motor Control Centers [MCC] E-MC-7C and E-MC-7E due to a locked in under-voltage signal from relays E-RL Y-27X/7 and E-RL Y-62/7. There were no abnormal system responses that could not be attributed to the blown fuse. The affected Motor Control Centers were restored at 04:07. E-SM-7 was transferred back to the Startup Transformer and restored at 04:39.
Cause
The temporary loss of E-SM-7 and resulting emergency diesel actuation was due to a human performance error that occurred when the electrician reconnected the meter test lead incorrectly. When discovering the detached test lead, the electrician proceeded to re-attach it to the meter and connected it incorrectly. The electrician did not stop to analyze the configuration of the test leads and did not seek a peer check. A supervisor was not contacted for assistance or for direction about discontinuing the procedure until the right equipment was available for proper staging of the testing meters.
An additional causal factor occurred when the maintenance electricians failed to stop the testing procedure when the proper length of test leads were not available and failed to engage their supervision before proceeding. Placing the testing equipment on a stable platform or on the floor required test leads long enough to reach the cabinet's terminal strip. Rather than obtaining long leads, the technicians used the available short leads and attached the Fluke meters to the cabinet wall with tape.
Training was not part of the cause as no knowledge or skill deficiency was identified in the investigation.
26158A R3 NRG FORM 366A (01-2014) Immediate Corrective Action
2. DOCKET
05000 397 2015 - 004 - 00 The following immediate corrective actions were implemented: (1) Direction was provided by plant management to craft to no longer tape test instruments to cubicle walls; (2) Completed For Cause Fitness-for-Duty testing to craft and supervisor involved in incident; (3) Discussed in daily plant briefings about utilizing the correct tools for the job; (4) Individuals involved were coached on proper use of test leads and equipment; and (5) Replaced blown fuse (F25-2) and E-SM-7 was restored and realigned to the Startup Transformer.
Additional Corrective Actions The following further corrective actions are being implemented to prevent future occurrences of similar conditions: (1) The human performance behaviors that led to this event were addressed via the culpability model for current Columbia Generating Station personnel; (2) A work request has been generated to install applicable insulated banana jack test connections at the terminal strip used for the related testing; and (3) Purchased long leads and test connections to be used with Fluke 43 meters.
Operating Experience and Previous Occurrences The Licensee Event Reports (LERs) database was searched for similar incidents previously reported by the Columbia Generating Station. The following previous occurrences were found:
- LER# 94-014-00 (07/06/1994) - Engineered Safety Feature Actuation Due to Test Lineup. l&C Technicians were backfilling instrument lines to support excess flow check valve testing. A line up error created an invalid low level indication which caused several automatic actions including a Low Pressure Core Spray (LPCS) [BG] system actuation and injection.
- LER# 96-001-00 (04/25/1996) - Inadvertent ESF Actuations Due to Tripping of Temporary Power Supply to IN-3 by Outage Electricians. Electricians inadvertently opened the fused disconnect supplying the Uninterruptible Power Supply (UPS) [UJX] inverter IN-3 loads, causing a loss of power to the loads. This resulted in ESF actuations [JE] and containment isolations.
- LER# 98-013-00 (08/05/1998) - Engineered Safety Feature (ESF) Actuations Due to Deenergization of Vital Electrical Bus SM-8. During investigation of the cause for apparent emergency diesel generator 2 (DG-2) [EK] voltage regulator problems, vital electrical bus SM-8 [SWGR] and its associated loads were deenergized causing several ESF system isolations and half-isolations to occur.
Assessment of Safety Consequences
Division 2 equipment was supporting all safety functions at the time of the event and the event was isolated to Division 1 equipment; therefore, there was no actual safety consequence to the event. There was no equipment damage, dose exposure, or injuries to station personnel. There was no change in plant status or operating condition and there was no actual risk to the public at any time.
Energy Industry Identification System Information Energy Industry Identification System information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [X] and [XX] throughout the body of the narrative.
26158A R3 NRC FORM 366A (01-2014)