05000285/LER-2012-019, Regarding Traveling Screen Sluice Gates Found with Dual Indication

Regarding Traveling Screen Sluice Gates Found with Dual Indication

ML12298A356
Person / Time
Site:	Fort Calhoun
Issue date:	10/15/2012
From:	Cortopassi L Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LIC-12-0149 LER 12-019-00
Download: ML12298A356 (5)

LER-2012-019, Regarding Traveling Screen Sluice Gates Found with Dual Indication

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat
2852012019R00 - NRC Website

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Docket'No. 50-285:`

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On August 14, 2012, at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> Central Daylight Time, Operations was cycling all 6 traveling screen sluice gates when it was Identified that traveling screen sluice gate CI*.-14E motor was stopping on high torque and provided indication that the gate was approximately 8 inches open. Traveling screen sluice gate CW-14C was also stopping on high torque and providing indication the gate was not fully closed. During a flooding event, these sluice gates are credited to fully close allowing control of the intake structure ceMl level with the raw water pumps. Cell level is maintained below elevation 1007-foot 6-inches. This is the point at which the raw water pump bay could becom floode causing a loss of raw water to the component cooling water heat exlhangers. On August 25, 20612, divers reniove-the sediment nddebri."p from all elice gate bottoms returning the *luica gates' capablty-tobely-,.close'd In the event of a design bI:asisflood.-

The apparent cause of the failure of t6h.

luice gates'to ulclose -was debris under the gates. A cause analysis Is in-process and when completed; thisLER will besupplemented.,

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• vco uo CONTINUATION SHEET 1.A PAW.__

Fort Calhoun Station 05000285 M-2 OF 4

2012 019

• 0 BACKGROUND

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Fort Calhoun Station (FCS) S a tw6-lp reictor coolant yem ofCombustion Engin (ing (C")

design.

Foraw water pumps are, inst..0.d in, te !ntaestru:tir pum house to prik'.* scr.ened river wAter th omponent 6oplino heat exchanges Protection for the raw water pumps and their drives against floods is provided at three elevations. The pumps, are permanently protected. against any w"ter level up to 0e*vaion 1,007.5,et by te Class I, concrete substructuieof the intake buldin'g. Protecti.n agains the 1 009.5-fooekt anrid 1401. -4if lo is.ýrovided by gasketed steef closures at exterior doorway openings arid the screen Wash disc-harg trough. The water level inside the intake cells can be controlled by pre-positloning the exterior sluice gates.(i.e, before floodwater reaches the elevation that prevents access to the sluice gate manual actuators), to severely rst Ithe inflow into. the cells,,,.!ntke. celllovel is. then controlled byý vring the raw water pump(s) outr"emove the inlet flo USAR Figure9.8-1 Isprovlded below for reterendo.

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Pa iIr Gate$~~

The basic safety related function of the raw water system is to provide a cooling medium for the component. cooling water system.,"he raw water system also provicies,.drect cpotlng.-forth following safety-related components inthe event, that thet component,cooling water system:f..unavailable: the.

shutdown cooling heat-exchangers, the hgWow,, pressure safety Injection pump bearing oil and seal coolers, the containment spray pump bearing oil and seal coolers, and the control room air conditioners.

NRC FORM 36eA (10-2010)

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The circulating water pumps, which take suction from the intake cells, have been secured for approximately 18 months, in part., creating a low flow conditn and may b causing addtal to bu Id-up.

Technical Specification (TS), Umiting Condition for Operation (LCO) 2.4, Containment Cooling, defines the minimum requirements for reactor criticality (except for tow-temperature physics tests). The reactor maybe made critical with one inoperable raw water pump; however, LCO action statements shall apply.

TS.LCO, 2.16, R"ver Level, provides the Maximum river.level, as measuredsat the intake structure, as 1009 feet'for 'eactorshUtd6wn6d I1 2 feet And ring as thlevel to institute the emergency plan to protctthe plnt.

EVENT DECR1I

l On. Augu 2012, at rox e

,hous Central Daylight Time, w cying all 6 taeigseesliegtswentwaIeniedtatring ngsre liegt C-4)motor was stopping on high torqUe and provided indication that the gate was approximately 8 inches open.

Traveling screen sluice'gate (CW-1 4C) was also stopping on high torque and providing indication the gate was:not fully cosed. During afoding, event, these suic, gates are credited:.to fully.clseqal9wing control of the 6"te" s'Ctructre' el eewith'O 4t rw wae pumps. Cell leelis mntaine belowii

.elevation 1007-f~oot.6-n s.

es,-This. thepointt wth"ich t"heraw water pump bay *uld become flooded causng a toss 0fi Ara water tothe.to"

.e og water het exchangers. At the time of'discovery, FCýSwa shto "M L Mod 5" Ir addMQ.tO the raw water pumps, the circulating Water pumps take suon from the iake cells. These'pumps have been secured for approximatel-18 months creating a low f condition which may, in-iart, be causlng additional sediment to build-up where the sluice gates rest when closed.

On August 15, 2012, FCS engineers provided reasonable assurance that the indication was incorrect and that the sluice gates were closed. FCS does not have a TS delineating sluice gate operability.

The functionality determination required that divers confirm that the sluice gates were closed. On August 25, 2012, divers documented the following gaps between the sluice gate bottom edge and the concrete resting floor:

CW-14A: 1.6 inches CW-148: 1 Inch CW-14C: 1 inch CW-140: 1 inch CW-14E: 3 inches CW-14F: 2.5 inches On August 25, 2012, divers removed the sediment from all sluice gate bottoms and a 3-inch tree branch from CW-14E, returning the sluice gates' capability to be fully closed in the event of a design basis flood.

On September 17, 2012, this event was determined to be reportable under 10 CFR 70.73(a)(2)(v)(B),

any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.

I NRC FORM 3M6A (10-2010)

(10-210)

LICENSEE EVENT REPORT (LER) U. NUCLEAR REULTORY ComMO CONTINUATION SHEET

1. ACLrrY NAME WOMIEN

& PAGE Fort Calhoun Station 0I0=6 Y

W, 4

OF 4

2012

- 019 0

NARRATIVE

CONCLUSION The apparent cause of the failure of the sluice gates to fully close was debris under the gates. A cause analysis is in-process and when completed, this LER will be supplemented to Include any additional causes that are identified.

CORRECTIVE ACTIONS

A preventive maintenance activity was previously created to cycle CW-14A/B/C/D/E/F through their full range of travel in ensure availability for flood mitigation. This activity is currently performed monthly and is performed to ensure the sluice gates perform their safety function.

A flood impairment has been placed in the control room to provide direction for verifying full closure and flushing sediment and debris that could prevent the gates from fully closing during a design flooding event.

A cause analysis is in-process and when completed, this LER will be supplemented to include any

SAFETY SIGNIFICANCE

The loss of the ability to close the intake structure sluice gates during flood conditions could lead to the loss of the raw water pumps which supply cooling water component cooling water heat exchangers. The raw water system also provides direct cooling for the following safety related components in the event that the component cooling water system is unavailable: the shutdown cooling heat exchangers, the hightlow pressure safety injection pump bearing oil and seal coolers, the containment spray pump bearing oil and seal coolers, and the control room air conditioners.

In the event of a DBA, the component cooling water system Is designed to provide sufficient cooling water to the engineered safeguards equipment.

SAFETY SYSTEM FUNCTIONAL FAILURE This event does result In a safety system functional failure in accordance with NEI-99-02o PREVIOUS EVENTS A cause analysis is In-process and when completed, this LER will be supplemented to include any previous events that are identified.

NRC FORM 36A (10-2010)