05000388/LER-2016-001

LER-2016-001, Secondary Containment Breach due to Simultaneous Opening of Airlock Doors Due to Degraded Latch Mechanism

Susquehanna Steam Electric Station Unit 2
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
3882016001R00 - NRC Website

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 Internet 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.

CONDITIONS PRIOR TO EVENT

Unit 2 — Mode 1, 100 percent Rated Thermal Power Unit 1 - Mode 5, 0 percent Rated Thermal Power

EVENT DESCRIPTION

On March 29, 2016 at approximately 23:00, two employees leaving the Unit 2 Turbine Building [EIIS System Identifier: NM] entered the Turbine Building to Reactor Building airlock [EIIS Component Identifier: AL] on elevation 676'. Prior to opening the airlock door [EIIS Component Identified: DR], employees verified a green light was present, indicating the opposite airlock door was closed. The first employee entered the airlock while the other employee held the Turbine building door. As the second employee entered into the airlock, the airlock alarm was heard. At this time, a rush of air was observed from the Reactor Building [EIIS System Identifier: NG] side of the airlock, forcing the door open (Door 120A). Both individuals quickly closed the doors, followed by a peer check to verify each door was properly shut. The individuals then proceeded through the Reactor Building door to the nearest phone and informed the Control Room [EIIS System Identifier: NA] of the event.

CAUSE OF EVENT

The direct cause of this event is normal wear of the airlock door latch. Based on investigation performed, the Door 120A latch was determined to be sticking inside the crash bar. This prevented the Reactor Building airlock door from properly latching and staying latched when differential pressure was applied to the door upon entering the airlock from the Unit 2 Turbine Building side.

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 Internet 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.

ANALYSIS/SAFETY SIGNIFICANCE

Technical Specification 3.6.4.1 Surveillance Requirement 3.6.4.1.3 requires that one secondary containment access door in each access opening is closed. This event is being reported pursuant to 10 CFR 50.73(a)(2)(v)(C) as having both Secondary Containment airlock doors momentarily open simultaneously results in a condition that could have prevented fulfillment of a safety function to mitigate the consequences of an accident by controlling the release of radioactive material.

There was no actual safety consequence as a result of this event. Engineering analysis of this event has determined that secondary containment could have performed its safety function of isolating, as assumed in the accident analysis, and also of re-establishing 0.25 in w.g. 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 supporting the system's ability to fulfill the safety function.

CORRECTIVE ACTIONS

As discussed above, the cause of this event was attributed to normal wear of the airlock door latch. A work order was written to investigate and repair the Door-120A latch as necessary. Maintenance lubricated and tightened screws on the latch mechanism; the door was then successfully tested and confirmed operable by Operations.

No regulatory commitments are associated with this report.

COMPONENT FAILURE INFORMATION

Reactor Building Elevation 676' Door-120A — Normal Wear.

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 internet 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.

PREVIOUS SIMILAR EVENTS

The following recent LERs involving loss of Secondary Containment due to door issues:

Open Due to Random Occurrence," dated April 18, 2016.

Open Due to Random Occurrence," dated April 18, 2016.

had not been Properly Latched," dated January 29, 2016.

Containment Boundary Door 104-R Breached," dated September 18, 2015.

Door Found Ajar," dated June 25, 2015.

Specification Surveillance Requirement 3.6.4.1.1," dated June 10, 2015.

Momentarily Open Due to a Personnel Error Resulting in Entry into Secondary Containment Technical Specification Limiting Condition for Operation," dated December 31, 2014.