05000387/LER-2017-004

LER-2017-004, Secondary Containment Declared Inoperable Due to Failure of an Exhaust Fan Breaker.

Susquehanna Steam Electric Station Unit 1
Event date:	06-09-2017
Report date:	0-0-2017
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
3872017004R00 - NRC Website

LER 17-004-00 for Susquehanna, Unit 1, Regarding Secondary Containment Declared Inoperable Due to Failure of an Exhaust Fan Breaker

ML17216A286
Person / Time
Site:	Susquehanna
Issue date:	08/04/2017
From:	Berryman B Susquehanna, Talen Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7628 LER 17-004-00
Download: ML17216A286 (4)

comments regarding burden estimate to the Information Services Branch (T-2 F43), 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.

Susquehanna Steam Electric Station Unit 1 05000387 NUMBER NO.

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 3, approximately 0 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power Unit 1 was in the process of starting up following a Scram on 6/8/17, however, this did not contribute to the event. There were no structures, systems, or components that were inoperable on Unit 2 that contributed to this event.

EVENT DESCRIPTION

On June 8, 2017 at approximately 2206, at the start of restoration of the Reactor Building HVAC [EIIS Code:

NG] Unit 1 Zone 3 ventilation post Unit 1 SCRAM, Operations placed the 'A' Reactor Building Zone 3 Filtered Exhaust Fan [EIIS Code: FAN] in service. The 'A' Reactor Building Zone 3 Supply Fan [EIIS Code:

FAN] started but the 'A' Reactor Building Zone 3 Exhaust Fan [EIIS Code: FAN] did not. With the Filtered Exhaust Fan in service, the supply air was greater than the exhaust air which resulted in a loss of differential pressure.

6/9/17 0441: Operations entered Technical Specification (TS) 3.6.4.1 due to Secondary Containment being inoperable during the start of the Zone 3 fan.

6/9/17 0449: Operations cleared TS 3.6.4.1.

6/9/17 0509: Secondary Containment Zone 3 differential pressure lowered to 0" WG as a result of the Reactor Building HVAC fans tripping and restarting several times. The required differential pressure per Surveillance Requirement 3.6.4.1.1 could not be maintained. Operations placed Unit 1 Zone 3 Filtered Exhaust in the STOP position.

6/9/17 0941: Operations entered LCO 3.6.4.1 due to Secondary Containment being inoperable while restoring Unit 1 Zone 3 HVAC.

6/9/17 1010: While restoring Unit 1 Zone 3 HVAC, a bell alarm for the Reactor Building Zone 3 Exhaust Fan supply breaker could not be reset.

6/9/17 1015: Operations placed the Unit 1 Zone 3 system in service using the 'B' Unit 1 Zone 3 fans. The 'A' Reactor Building Supply Fan and 'A' Reactor Building Filtered Exhaust Fans were placed in STANDBY.

The 'A' Reactor Building Exhaust Fan was left in STOP.

6/9/17 11:11 The Maintenance investigation revealed that the terminal connection was broken in the supply breaker [EllS Code: BKR] for the 'A' Reactor Building Zone 3 Exhaust Fan.

Maintenance replaced the ring terminal and re-terminated the wire. The exhaust fan was successfully Zone 3 Secondary Containment fans. Zones 1 and 2 were not affected. This event is being reported under 10 CFR 50.73(a)(2)(v)(C) as a condition that oculd have prevented the fulfillment of a safety function.

comments regarding burden estimate to the Information Services Branch (T-2 F43), 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.

The cause was determined to be a broken ring terminal on the breaker [EIIS Code: BKR] which prevented the fan from starting.

ANALYSIS/SAFETY SIGNIFICANCE

An engineering evaluation was performed and concluded that secondary containment could have performed its safety function of isolating as assumed in the accident analysis and also of re-establishing 0.25 inches vacuum (drawdown) within the assumed accident analysis time (10 minutes). Therefore, the subject event did not cause a loss of safety function. This event will not be counted as a safety system functional failure (SSFF) for the NRC performance indicator based on the engineering analysis that shows there was no loss of ability to fulfill the safety function.

CORRECTIVE ACTIONS

Maintenance replaced the ring terminal and re-terminated the wire and the exhaust fan was placed back in service.

PREVIOUS SIMILAR EVENTS

The following are recent LERs involving loss of secondary containment due to component failures:

2016.

June 22, 2015.

25, 2015.

Supply Plenum Screens," dated February 2, 2016.