05000388/LER-2017-007

LER-2017-007, Secondary Containment Declared Inoperable Due to Supply Air Flow

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
3882017007R00 - NRC Website

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.

NUMBER NO.

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, approximately 100 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.

EVENT DESCRIPTION

On August 8, 2017 at approximately 2043 hours0.0236 days <br />0.568 hours <br />0.00338 weeks <br />7.773615e-4 months <br />, Secondary Containment Zone 2 [EIIS Code: VA] experienced a loss of differential pressure (dP) following replacement of the Zone 2 ventilation supply side filters. All fans were running; however, the 'B' discharge damper controller output was found to be outside of its normal operating band.

The following is a timeline of events:

8/8/17: The filters on Zone 2 ventilation supply side were replaced during day shift.

8/8/17 2030: The Control Room received Reactor Building (RB) [EllS Code: NG] FAN ROOM Elevation 779' 2C275 PANEL trouble ALARM.

8/8/17 2043: Operations reported the local alarm was for RB hi-lo DP and RB Zone 2 dP is 0.15" vacuum water gauge. All fans are running, but noted that PDD-27578B (2V205B Discharge Damper) is indicating dual indication.

8/8/17 2044: Entered Technical Specification 3.6.4.1 for Unit 1 and Unit 2 due to Secondary Containment inoperable with Zone 2 dP 8/8/17 2052: Operations restored building dP to >0.25" vacuum water gauge after slight adjustment to the Zone 2 inlet dampers and swapping Zone 2 Exhaust Fans ("A" in-service, "B" inStandby.

8/8/17 2112: Exited condition for Technical Specification 3.6.4.1 for both units.

As a result, Technical Specification Surveillance Requirement (SR) 3.6.4.1.1 was not met. Zone 2 differential pressure was recovered to > 0.25" vacuum water gauge following slight adjustment of the Reactor Building Zone 2 inlet dampers at approximately 2052 hours0.0238 days <br />0.57 hours <br />0.00339 weeks <br />7.80786e-4 months <br />. Zones 1 and 3 were not affected.

CAUSE OF EVENT

The cause was determined to be increased supply air flow following the replacement of the supply side filters and less than adequate written communication in the work instructions on the impact of filter replacements on reactor building differential pressure.

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.

NUMBER NO.

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

Corrective actions include revising the Preventative Maintenance work instructions to ensure operations support is available to monitor output of the discharge damper controller and to adjust the inlet damper as needed during filter replacement.

PREVIOUS SIMILAR EVENTS

The following are recent LERs involving loss of secondary containment due to fan issues:

Safety Function," dated September 6, 2017.

dated August 18, 2017.

Safety Function," dated August 4, 2017.

2016.