05000410/LER-2014-005

LER-2014-005, Secondary Containment Inoperable Due to Sustained High Winds

Nine Mile Point Unit 2
Event date:	3-12-2014
Report date:	5-9-2014
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
Initial Reporting
ENS 49906	10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
4102014005R00 - NRC Website

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A. PRE-EVENT PLANT CONDITIONS:

Prior to the event, Nine Mile Point Unit 2 (NMP2) was operating at 15 percent power.

B. EVENT:

On March 12, 2014 at 1422, NMP2 declared secondary containment inoperable.

Secondary containment differential pressure (dP) went positive during a significant wind condition originating from the northeast direction associated with Winter Storm Vulcan.

Operations entered TS 3.6.4.1, Condition A and N2-EOP-SC, Secondary Containment Control- Flowchart, after Division 2 Standby Gas Treatment System (GTS) was started and placed in manual control to maximize negative dP. The reactor building was isolated to support maintaining the reactor building dP negative in accordance with N2-OP-52, Reactor Building Ventilation, at 1630. This resulted in the isolation of the reactor building vent radiation monitor and associated loss of emergency assessment capability as reported in Event Notification 49906.

Service water valves were also throttled to control reactor building temperature due to reactor building isolation. As conditions evolved, the secondary containment was declared operable at 1700 when secondary containment vacuum was restored to greater than 0.25 inches of vacuum water gauge. Subsequently, TS 3.6.4.1, Condition A was exited.

Nine Mile Point Unit 1 (NMP1) was unaffected by the occurence of secondary containment inoperabilities at NMP2.

The loss of secondary containment dP has been entered into the plant's corrective action program as CR-2014-002028.

THE EVENT:

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

Nine Mile Point Unit 2 05000410

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

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

March 12 1410: Declared Division 2 GTS inoperable for dP control, placed 2GTS*PV5B in manual.

1422: Entered TS 3.6.4.1, Condition A to restore secondary containment.

Entered N2-EOP-SC due to secondary containment pressure being positive.

Station announcement made on EOP entry including direction to ensure all air locked doors are shut.

1526: Declared Division 2 GTS operable. PER USAR 6.5.1.5 with 2GTS*PV5B isolated Division 2 GTS is operable.

1630: Isolated the secondary containment to support maintaining negative dP.

Entered ODCM D.3.3.2, Conditions D and F (Reactor Building Vent Radiation Monitor) 1700: Exited TS 3.6.4.1, Condition A. Secondary containment dP maintained greater than 0.25 inches vacuum water gauge.

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

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

F. METHOD OF DISCOVERY:

This condition was recognized by Operations as they monitored secondary containment dP during the wind storm.

G. MAJOR OPERATOR ACTION:

Operations placed the GTS in manual to maximize negative differential pressure. TS 3.6.4.1, Condition A was entered due to the inability to maintain the required dP. The reactor building was isolated to support maintaining the dP as negative. Service water valves were throttled to control secondary containment temperature due to its isolation. The dP subsequently returned to greater than 0.25 inches vacuum water gauge.

H. SAFETY SYSTEM RESPONSES:

This event was caused by high winds from Winter Storm Vulcan. The Secondary Containment ventilation and the GTS equipment performed as expected.

II. CAUSE OF EVENT:

The positive dP was related to sustained high winds from the northeast associated with Winter Storm Vulcan.

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. In addition, isolation of the reactor building vent radiation monitor which occurred during the event is reportable under 10 CFR 50.72 (b)(3)(xiii) and represented a loss of emergency assessment capability.

The event of the secondary containment dP dropping below the required TS minimum value is attributed to outdoor environmental conditions, specifically high winds associated with a winter storm. Operator actions taken on March 12, 2014 to address the high wind conditions and increasing secondary containment pressure were based on monitoring available meteorological data and were consistent with plant procedures. Procedure N2-OP-52 provides operators with direction to place the GTS in service and/or isolate the Reactor Building to maintain a negative pressure in the secondary containment. The causal evaluation of this event identified that N2-OP-52 does not provide this direction prior to exceeding the TS limit for secondary containment dP. This lack of procedural direction was identified as the apparent cause of this event.

The required TS Limiting Condition for Operation (LCO) action statement during this event was entered and subsequently exited once the secondary containment dP was restored to above the required TS minimum value. In all cases, the TS required 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.

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 AFFECTED SYSTEMS TO PRE-EVENT NORMAL

STATUS:

Operations entered the action statement for TS 3.6.4.1, Condition A and associated plant procedures to return the affected systems to pre-event status. These steps combined with placing the GTS in operation returned the secondary containment to pre-event status.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

The corrective action planned involves revising N2-OP-52 to provide direction to initiate GTS and isolate the reactor building during high wind conditions prior to exceeding TS limit for secondary containment dP.

A. FAILED COMPONENTS:

There were no failed components that contributed to this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

secondary containment dP drop below the TS minimum value. The LER noted this plant condition has occurred numerous times in the past when the secondary containment has been declared inoperable as a result of the secondary containment dP dropping below the required TS minimum of negative 0.25 inches water gauge. The direct causes of the secondary containment dP dropping below the required TS minimum value have been attributed to changes in outdoor environmental conditions (changing wind direction and velocity), changing of lineups or equipment failures associated with the normal non-safety related Reactor Building Ventilation System. In each case, the required TS Limiting Condition for Operation (LCO) action statement was entered and subsequently exited once the secondary containment dP was restored to above the required TS minimum value. In all cases the TS required completion time was not exceeded.

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