CooperNuclearStationCoolingWaterIntakeStructurePresentationtoEPAMarch2,2009What’DiscussWe reGoingtoDiscuss•Wherewearelocatedlocated•Intakestructuredesign&featuresCh llf•aengesweace–Sedimentation–Debris•Whatwe’vedonetomeetthechallenges

# Copyrighted page(s) have been removed from

this document.

Please contact the EPA Docket Center, Public

Reading Room to view this document.

Address:

1301 Constitution Ave, NW

Room 3334

Washington, DC 20004

Telephone:

202-566-1744

Fax:

202-566- 9744

Email:

docket-customerservice@epa.gov6CooperNuclearStation7IntakeDescription•The Intake Structure provides a source ofMissouriRiverwaterto:–Circulating Water System, which cools the MainCondenser, and–Service Water System, which cools both safety relatedand non‐safety related components.•CoolingwaterisdrawnfromtheriveroveraCoolingsloping weir wall.–Wallwasinstalledintheearly1970stocontrolinstalledcontrolsediment inflow into the intake.–Wall was designed based on river flows typical of the1960dl70s anearys.IntakeDescription•Traveling Water Screens (TWS) are installeddownstream ofthe Intake Structure Trash Racks.–The purpose of the TWS is to remove debris from the riverwater prior to its supply to the suction of the fourCirculating Water (CW) pumps and the four Service Water(SW) pumps.–There are nine TWS; two for each of the four CW pumpsand one for the SW pumps.•CirculatingWater(CW)systemsforplantcondensersduringnormaloperations:Fidli000–ourpumpsprovecoongwaterat159,gpmeach(1417cfstotal)and–Threeotherpumpsprovide30,000gpm(67cfstotal)ofserviceandfirewater.IntakeStructureSediment•The Cooper intake was designed in accordancewithrecognizedcriteriaforintakesonsandyrecognizedcriteriaintakesrivers.–Majority of the suspended solids was expected to passthrough the circulating water system,–Some material was also expected to settle out in theintakeandreachanacceptableequilibriumwhentheacceptableequilibriumpumps were placed in operation.–This, however, did not hold true in the case of Cooperand attempts to operate the pumps on a continuousbasis were hampered by the jamming of the travelingscreens due to high deposition ofsediment in front ofand behind them.Sediment•There are apparently several reasons for this sedimentdeposit:–The river has high velocities and sediment carryingcapacity at this location and the sudden reduction invelocities within the intake passages tends to settle thel ti lhb ttdi tl di klreaveyeavyoom semenoaqucy.–The upstream portion of the protective sheet pile cell leftin place after construction (to serve as a remedy to apossiblebargeimpactproblem)createseddiesresultinginpossibleproblem)createsresultingincrease of sediment deposition in the vicinity of andwithin the intake area.Therapidlyshiftingnormalriverbottomimmediately–rapidlyshiftingimmediatelyadjacent to the front face of the intake tends to be at ahigher level that the bottom of the intake. Material fromthriverbottomtentobecarriintothintak.edsedeeSediment•SedimentloadincreaseswithincreasedflowsfromNishnabotnarivers.thePlatteandNishnabotnarivers.•Lowerwaterlevelsincreasesthesedimentcarryingcapacity.•Sunkentrashanddebrisaccumulationsatthebtht hktlikiaseoferasracscanacewers,furtherslowingthewatervelocityandcausingdi tmoresementodropout.Sediment•The increased siltation has forced:–Pump shutdowns after clogging up the trashracksand reducing the head available for pumping.–Mechanical removal methods such as excavatorsand divers have offered CNS only short‐terml tisouons.–Significantly increased traveling water screendlbldmaintenance anoperationaproems, increasestrainer backwashes, and restricted flow passageswiththeIntakeStructureCirculatingWaterbaysStructureCirculating.Sedimentation•Themajorpreventivemeasurealreadyinplacetoaddresstheseasonalsedimentationconcerntohavediversmanuallycleandebrisfromthetrashracksandde‐sandtheIntakeStructurebays.•Thiscleaningisperformedevery6months,inthespringandinthefall.–Thespringcleaningaddressestheincreasedsandbuildupratefromthelowriverlevelsandisprngrunoff.–Thefallcleaningremovesthesunkentrash/debriswhichlincreaseshsedimentas /deb sa soc easest esed e tbuilduprate.CloudSuspendedofSuspended0.5MMSandDebris•Debris lodges in the condenser tubes–Reduces condenser efficiency and requires the frequent backwashingofthe Main Condenser in an attempt to dislodge the accumulateddebris.–Creates clogging and high differential pressures within the strainers,requiring increased cleaning to maintain system operability.•During power operation, condenser backwashing provides short‐term improvement to condenser performance, but must berepeatedonapproximatelyaweeklybasis.repeatedapproximately–There were 45 backwashes during 2002–Each backwash evolution requires a plant power reduction. In 2002,the net CNS generation loss associated with condenser backwashingi tl3220MWhwas approxmaey,rs–In addition, the backwash process is not fully effective in removing alldebris. The debris that cannot be dislodged must be removed by handduringeach refuelingoutage.DebrislodgedinMainCondenserTypicalRiverTrashWhat’DoneWe ve•Cutweirwallandaddedturningvanes–Reducedsedimentbayssedimentintothe–Approx$2.2M•Changedscreendesign–Flowthroughtodualflow–Keeptrashcondenseroffcondenser–Approx$6M•OperationalChallengesremain–Continuetobackwashcondenser–ContinueintakestructuretoContinuetodredgestructuremechanicallyremovesedimentDualvs.ThruFlowScreens