05000249/LER-2016-001

LER-2016-001, Alert Declared from Unit 3 HPCI Auxiliary Oil Pump Motor Fire

Dresden Nuclear Power Station, Unit 3
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
LER closed by
IR 05000237/2016010 (5 December 2016)
2492016001R00 - NRC Website

LER 16-001-00 for Dresden Nuclear Power Station Regarding Alert Declared from Unit 3 HPCI Auxiliary Oil Pump Motor Fire

ML16239A393
Person / Time
Site:	Dresden
Issue date:	08/25/2016
From:	Karaba P J Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SVPLTR 16-0047 LER 16-001-00
Download: ML16239A393 (4)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000-249

3. LER NUMBER

2016 - 00 001

PLANT AND SYSTEM IDENTIFICATION

Dresden Nuclear Power Station (DNPS), Unit 3, is a General Electric Company Boiling Water Reactor with a licensed maximum power level of 2957 megawatts thermal. The Energy Industry Identification System codes used in the text are identified as [XX].

A. Plant Conditions Prior to Event:

Unit: 03 Event Date: 06/27/16 Reactor Mode: 1 Mode Name: Power Operation Event Time: 1042 CDT Power Level: 100 percent

B. Description of Event:

On 6/27/16 at approximately 1042 CDT, the High Pressure Coolant Injection (HPCI) [BJ] Auxiliary Oil Pump (AOP) motor failed during the performance of the quarterly operability run of the HPCI system. HPCI was the only system inoperable at the time. Alarms were received in the Main Control Room (MCR), and the HPCI turbine was immediately tripped. The HPCI steam inlet inboard isolation valve (3-2301-4) and HPCI main pump torus discharge minimum flow valve were closed (3-2301-14). The AOP motor was secured, and Equipment Operators standing by in an adjacent room were dispatched to investigate the AOP. Upon opening the door, active flames were visible at the top and bottom of the AOP motor along with light smoke in the room. This observation was immediately communicated to the MCR, and the fire was extinguished manually at 1045 CDT with a carbon dioxide fire extinguisher.

HPCI Room, and the Unit 2/3 Diesel Fire Pump automatically started due to the HPCI Room Fire Protection [KP] piping filling with water in anticipation of initiating the sprinkler system. However, initiation of the sprinkler system was not required since the fire was quickly extinguished. At 1050 CDT, an ALERT was declared. At 1319 CDT, the ALERT was terminated. The unit remained at full power throughout the evolution. On 7/7/16 at 1625 CDT, HPCI was returned to service.

This event is reportable under 10 CFR 50.73(a)(2)(v)(D), "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.

C. Cause of Event:

The Root Cause of the HPCI AOP motor failure is inadequate control of critical parameters when installing a DC shunt wound motor. The Failure Mechanism was high armature current with a stalled rotor. The Contributing Cause of the HPCI AOP motor failure is historical motor procurement evaluation standards were not rigorous enough.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000-249

3. LER NUMBER

2016 - 00 001

D. Safety Analysis:

The safety significance of this condition was low as it did not adversely impact the health and safety of the public. The fire did not cause a plant transient and did not impact any systems or equipment other than the HPCI system which was already declared inoperable for surveillance testing at the time of the event.

During the evolution redundant safety systems remained capable of performing each of the functions required by the safety analysis. The Isolation Condenser [BL] and Automatic Depressurization System [JE] remained in service and were capable of removing heat from containment while the vessel is at high pressure and lowering vessel pressure to allow for the low pressure Emergency Core Cooling Systems to inject. Both divisions of Low Pressure Coolant Injection (LPCI) [BO] remained capable of injection along with both divisions of Core Spray [BM].

Additionally, the Torus Cooling function of LPCI remained available as the primary method of heat removal from primary containment. The torus cooling function of LPCI provides the connection to the ultimate heat sink which was available throughout the evolution.

E. Corrective Actions:

The Unit 3 HPCI AOP motor was replaced and tested satisfactorily. Procedural controls will be enhanced for the installation of Shunt Wound DC motors with external variable shunt field resistors. An Extent of Condition review will be performed on all DC Shunt Field motors where the shunt field resistor range was determined for each motor and it will be verified that each were set appropriately. Additional training will also be conducted on DC motor operation.

Additionally, the list of DC electric motors requiring motor heaters will be validated and thermography will be performed on the listed motors to verify proper operation.

F. Previous Occurrences:

In 2015, the U3 HPCI AOP motor failed during planned maintenance due to carbon dust buildup inside the motor as a result of inadequate cleaning and inspection of the motor and commutator.

G. Component Failure Data:

Manufacturer Model S/N Type General Electric 5CD173XD817A800- NM245 N/A DC Shunt Wound Motor, 40 HP, 250 VDC, 3500 RPM