05000387/LER-2016-003

LER-2016-003, Unit 2 Zone 3 HVAC unable to maintain Zone 3 differential pressure greater than 0.25 in wg

Susquehanna Steam Electric Station Unit 1
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3872016003R00 - NRC Website

LER 16-003-00 for Susquehanna, Unit 1, Regarding Unit 2 Zone 3 HVAC Unable to Maintain Zone 3 Differential Pressure Greater Than 0.25 in wg

ML16127A083
Person / Time
Site:	Susquehanna
Issue date:	05/06/2016
From:	Franke J A Susquehanna, Talen Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7459 LER 16-003-00
Download: ML16127A083 (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 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.

V.kei V4g Susquehanna Steam Electric Station, Unit 1 05000387

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, 86.6 percent Rated Thermal Power Unit 2 — Mode 1, 100 percent Rated Thermal Power There were no other structures, systems, or components that were inoperable at the start of the event that contributed to the event.

EVENT DESCRIPTION

On March 8, 2016 at 0232 hours0.00269 days <br />0.0644 hours <br />3.835979e-4 weeks <br />8.8276e-5 months <br />, and while securing the Unit 1 Secondary Containment (El IS Code: NG) Zone III Heating Ventilation and Air Conditioning (HVAC) for a preventive maintenance activity, Zone III (Unit 1 and 2) Reactor Building (RB) differential pressure lowered to 0.16 inch of vacuum water gauge (WG). The alignment for the RB HVAC and Technical Specification (TS) 3.6.4.1 was entered for Unit 1 and Unit 2. The affected Zone III ventilation was restored to the original alignment and differential pressure recovered to > 0.25" inch WG at 0335 hours0.00388 days <br />0.0931 hours <br />5.539021e-4 weeks <br />1.274675e-4 months <br />.

On March 8, 2016, at 0937 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.565285e-4 months <br />, this condition was reported in accordance with 10 CFR 50.72(b)(3)(v)(C) for any event or condition that, at the time of discovery, could have prevented the fulfillment of the safety function.

There is no redundant secondary containment system.

In accordance with 10 CFR 50.73(a)(2)(v)(C), this LER is being submitted for an event or condition that could have prevented the fulfillment of the safety function of Secondary Containment to control the release of radioactive material.

CAUSE OF EVENT

The direct cause of the event was misalignment between upper and lower damper blades. The outside air dampers were originally designed to be maintained Full Open, but have since initial plant startup been throttled to control Reactor Building differential pressure. Over time, the alignment of the upper and lower blades has become misaligned, such that the top blades are more open than the lower blades, decreasing differential pressure. This misalignment caused a larger gap in the upper blades than was needed to restrict supply flow into Zone III when operations swapped the fans. The apparent cause is less than adequate design of the outside air dampers. The manual outside air dampers use a single level to control the entire bank of 13 louver blades. This design puts more stress on the linkages than if it were controlled by multiple levers.

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

The actual consequences from this event were entering the condition in TS for not satisfying the SR 3.6.4.1.1, and an eight hour notification of the event to the NRC. There is no redundant secondary containment system.

The safety-related function of the reactor building HVAC system is to isolate in the event of secondary containment isolation. Not maintaining the required pressure within secondary containment in this instance did not jeopardize this function because none of the isolation dampers or trip signals were impacted.

There were no actual or potential consequences to the health and safety of the public as a result of this event.

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

Zone III outside air damper alignment deficiency. Troubleshooting has since been completed.

The corrective action for this condition is an engineering change that allows the closing of the upper and lower damper sections to be operated separately for the reactor building HVAC supply systems. This action is scheduled to be complete in October of 2016.

PREVIOUS SIMILAR EVENTS

3.6.4.1"