05000410/LER-2015-001

LER-2015-001, Secondary Containment Inoperable Due to Sustained High Winds

Nine Mile Point Unit 2
Event date:	1-12-2015
Report date:	3-12-2015
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
4102015001R00 - NRC Website

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A. PRE-EVENT PLANT CONDITIONS:

Prior to the event, Nine Mile Point Unit 2 (NMP2) was operating at 100 percent power.

B. EVENT:

On January 12, 2015 at 1939, the Operator at the Controls at NMP2 noted Secondary Containment vacuum had decreased to less than 0.25 inches of vacuum water gauge and requested placing Standby Gas Treatment System (GTS) in service for Reactor Building (RB) presure control. Secondary Containment was declared inoperable and Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.4.1 Condition A was entered with a Required Action to restore secondary containment to operable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. At 1950 Operations started GTS Train "A". At 1956 secondary containment vaccum had been restored to greater than 0.25 inches of vacuum water gauge and TS LCO 3.6.4.1 Condition A was exited.

Nine Mile Point Unit 1 (NMP1) was unaffected by the inoperability of Secondary Containment at NMP2.

The event has been entered into the plant's corrective action program as IR# 2436393.

THE EVENT:

There were no inoperable systems, structures, or components that contributed to this event.

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

The dates, times, and major occurrences for this event are as follows:

January 12 1939: Entered TS LCO 3.6.4.1, Condition A, with a Required Action to restore Secondary Containment to operable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

1950: GTS Train "A" and 2GTS*FLT1A were started.

1956: Secondary Containment vacuum increased to greater than 0.25 inches vacuum water gauge and TS 3.6.4.1, Condition A was exited.

Nine Mile Point Unit 2 05000410 E. OTHER SYSTEMS OR SECONDARY FUNCTIONS All-bCTED:

No other systems or secondary functions were affected beyond the systems discussed in Section I.B.

F. METHOD OF DISCOVERY:

The condition was recognized by Operations as they monitored Secondary Containment vacuum during the period of sustained high winds.

G. MAJOR OPERATOR ACTION:

Operations placed GTS in manual to control Secondary Containment vacuum. TS 3.6.4.1, Condition A was entered due to exceeding the TS limit. Secondary Containment vacuum subsequently returned to greater than 0.25 inches vacuum water gauge.

H. SAFETY SYSTEM RESPONSES:

This event was caused by sustained high winds. The GTS equipment performed as expected.

II. CAUSE OF EVENT:

The apparent cause evaluation identified inadequate system balancing and failure to adjust the inlet damper after filter bag removal for seasonal readiness which allowed a volume increase that was beyond the control capability of the pressure control dampers during a high wind event.

III. ANALYSIS OF THE EVENT:

The event described in this LER is reportable under 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C) as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material.

The environmental condition that led to the event was a period of sustained high winds. Operator actions taken to address the high wind condition were based on monitoring available meteorological data and were consistent with plant procedures. Procedure N2-OP-52 directs operators to place GTS in service and/or isolate the Reactor Building to maintain vacuum in the secondary containment.

The apparent cause evaluation identified inadequate system balancing and failure to adjust the inlet damper after filter bag removal for seasonal readiness which allowed a volume increase that was beyond the control capability of the pressure control dampers during a high wind event.

TS 3.6.4.1 Condition A was entered and subsequently exited once secondary containment vacuum was restored to above the required TS value. The TS Required Action and its associated completion time was not exceeded. The secondary containment structural integrity, the ability to automatically isolate the non-safety related Reactor Building Ventilation System, and the GTS availability were not impacted. Secondary Containment would have continued to perform its intended safety function throughout the duration of the event.

Based on the above discussion, it is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel.

This event does not affect the NRC Regulatory Oversight Process Indicators.

IV. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN A1-1,BCTED SYSTEMS TO PRE-EVENT NORMAL

STATUS:

Operators declared secondary containment inoperable and entered TS LCO 3.6.4.1 Condition A with a Required Action to restore secondary containment to operable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Operators placed GTS in operation and returned the secondary containment to pre-event status.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

Corrective actions taken include adjusting Reactor Building intake dampers to lower supply fan flow to bring recirculation motor operated dampers into their control range and to adjust other system lineups until the dampers begin to Modulate.

The following corrective actions are planned:

Generate a procedure change for N2-OP-102, "Meteorological Monitoring" to ensure Reactor Building Ventilation damper repositioning is completed during bag filter installation or removal.

Perform an engineering review of the Reactor Building Ventilation system design and evaluate for potential design changes.

A. FAILED COMPONENTS:

There were no failed components that contributed to this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

NMP2 LER-2014-005, dated 05/09/2014, was submitted for Secondary Containment Inoperable due to Sustained high winds. The corrective actions taken included revising a plant procedure to provide direction to initiate the Standby Gas Treatment System and isolate the Reactor Building during high wind conditions prior to exceeding the Technical Specification (TS) limit for Secondary Containment differential pressure.

C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION

COMPONENT

IEEE 803 FUNCTION IEEE 805 SYSTEM

IDENTIFIER IDENTIFICATION

Reactor Building (BWR) N/A NG Reactor Building Ventilation System PDIC VA Standby Gas Treatment System N/A BH Reactor Building Vent Radiation Monitoring System MON IL

D. SPECIAL COMMENTS:

None