05000250/FIN-2017001-02
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Finding | |
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| Title | Failure of Vital Battery Chargers Due to Conductive Dust / Particulate Foreign Material Exclusion |
| Description | Annual Sample: (Opened) Unresolved Item (URI): Failure of Battery Chargers Due To Conductive Dust / Particulate Foreign Material Exclusion 18 a. Inspection Scope: The inspectors performed an in-depth review of AR 2183537 that documented an equipment apparent cause evaluation (EACE) associated with three Unit 3 battery chargers that tripped while in service. Thermo-Lag was being installed in support of fire protection modifications for Turkey Points transition to a risk-informed fire protection program, i.e. NFPA 805. The inspectors reviewed the associated corrective actions to verify they were completed as prescribed and that open actions were scheduled to complete commensurate with the safety significance of the activity. The inspectors walked down the battery chargers to verify selected corrective actions were completed and walked down the modification to HVAC unit V78 that was installed to prevent air from blowing directly into the battery charger ventilation louvers. The inspectors reviewed ARs that were generated during the EACE and evaluated the licensees disposition of these ARs to verify the licensees actions were in accordance with licensee procedure, PI-AA-104-1000, Corrective Action. During this inspection, on March 18, 2017, in a separate location of the plant, the 3A 4kV switchgear bus arc flashed in the reactor coil cubicle causing the 3A 4kV switchgear bus protective relay circuits to automatically deenergize the bus. The inspectors attended the licensees RCE failure investigation team meetings on this issue to obtain updates and gather facts on the arc flash and failed switchgear. The licensees RCE related to the 3A 4kV switchgear failure was in process at the end of this inspection period. The 3A 4kV switchgear room was undergoing Thermo-Lag passive fire barrier installation which was similar to the work in the new electrical equipment room (NEER) that housed the battery chargers. Documents reviewed are listed in the Attachment. This inspection constitutes one sample. b. Findings: Introduction: A URI was opened to determine if there is a performance deficiency related to the battery charger trips in the NEER and failure of the 3A 4kV switchgear bus. Description: On February 2, 2017, the 3A2 vital battery charger input breaker and motor control center (MCC) supply breaker tripped. Four minutes later, the D51 battery charger input breaker tripped. Subsequently, on February 8, 2017, the 3B2 vital battery charger input breaker and MCC supply breaker tripped, and a loud bang and possible flash were reported to have occurred in the lower level near the 4D MCC which supplies 480 Vac to the 3B2 charger. On February 13, the 4A2 and 4B2 battery chargers had difficulty load sharing with redundant battery chargers operating on their associated battery busses. The ARs associated with these separate issues include: AR 2184506, AR 2183540, AR 2183773, and AR 2185218. The licensee initiated an EACE on these issues, AR 2183537. For the battery charger trips that occurred on February 2, the licensee noted that Thermo-Lag work was in progress near the chargers in the NEER. At the time of the breaker trips, several employees were in the NEER performing cleanup from the Thermo-Lag activities. The licensee discovered a notable level of dust on horizontal surfaces in the NEER as well as inside the 3A2 and D51 battery charger cabinets. The licensee concluded the dust was conductive. The 3A2, D51 and 3B2 chargers, which were all located near each other and in the same room elevation, were cleaned and returned to service. The 4A2 and 4B2 battery chargers were also cleaned but it was noted those 19 chargers were in the same room but at a lower elevation. On February 8, the 3B2 charger tripped, despite it having been previously cleaned. It was noted at the time of the 3B2 charger trip that there were several employees installing Thermo-Lag in the NEER. The licensee concluded that the apparent cause of the breaker trips was conductive dust/particulate that may have been created by Thermo-Lag passive fire barrier installation in the vicinity of the battery chargers. The dust/particulate became airborne and settled on charger components. Corrective actions included cleaning all the chargers in the room and installing a modification which provided a sheet metal barrier on top of the D51, 3A2 and 3B2 battery chargers to deflect air from HVAC Unit V78 being blown directly into the louvered charger electrical cabinets. On March 18, 2017, in a separate location of the plant, the Unit 3A 4kV switchgear room, the 3A 4kV switchgear bus arc flashed in the reactor coil cubicle. The arc flash resulted in an explosion and the 3A 4kV switchgear bus was automatically deenergized by protective relay circuits. Similar to the NEER that housed the battery chargers, the 3A 4kV switchgear room was undergoing Thermo-Lag passive fire barrier installation. The deenergized 3A 4kV switchgear bus resulted in a Unit 3 automatic reactor trip. This event and NRC follow-up is described in section 4OA3 of this report. The licensee promptly chartered an RCE team to investigate the failure of the 4kV bus. The licensee noted that prior to the arc flash there were several employees in the 3A 4kV switchgear room performing similar Thermo-Lag installation. As an immediate corrective action, the licensee stopped all Thermo-Lag installation work in the entire fleet. The licensees RCE plan included determining if there were any common causes with the battery charger trips and the 4KV switchgear failure due to Thermo-Lag installations. A URI was identified because additional review is needed to determine if there were any common causes between the battery charger trips and anomalies and the 3A 4kV switchgear bus arc flash and to determine if this issue of concern constitutes a violation. Specifically, the inspectors will review the licensees RCE of the failed 4kV switchgear to determine if there are causes and corrective actions which were not identified during the investigation of the battery charger trip EACE, and if corrective actions could have prevented the 3A 4kV switchgear bus arc flash. (URI 05000250/2017001-02, Failure of Vital Battery Chargers Due to Conductive Dust / Particulate Foreign Material) |
| Site: | Turkey Point  |
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| Report | IR 05000250/2017001 Section 4OA2 |
| Date counted | Mar 31, 2017 (2017Q1) |
| Type: | URI: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | J Orr J Reyes N Hobbs R Carrion A Butcavage T Morrissey J Patel A Wilsond Orrj Reyes L Suggs |
| CCA | H.1, Resources |
| INPO aspect | LA.1 |
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Finding - Turkey Point - IR 05000250/2017001 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Turkey Point) @ 2017Q1
Self-Identified List (Turkey Point)
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