WIXLIB

ELECTRO HYDRAULIC CONTROLSYSTEMChapter 3.2

OBJECTIVES1. Identify the purposes of the Electro HydraulicControl (EHC) system.2. Describe the significance of reactor pressurecontrol to BWR operation.3. Describe how the system accomplishes itspurposes.

OBJECTIVES4. Recognize the purpose of the following limiters:a. Load Setb. Load Limitc. Maximum Combined Flow

OBJECTIVES5. Recognize the purpose, function andoperation of the following EHC systemsubsystems:a.b.c.d.e.Pressure Control UnitSpeed Control UnitDesired Load Control UnitValve Control UnitHydraulic Power Unit

OBJECTIVES6. Given Figure 3.2-1, describe how the systemoperates to accomplish the following:a. NormalNl steadyt d statet t power operationstib. Power maneuveringc. Plant shutdown and cooldown

OBJECTIVES7. Describe how the EHC system interrelateswith the following systems:a.b.c.d.MainMi StSteamCondensate and FeedwaterReactor ProtectionTurbine Building Closed Loop Cooling Water

PURPOSEThe purposes of the EHC System are to: provide normal reactor pressure control bycontrolling steam flow consistent with reactorpower control reactor pressure during startup, heatup,andd cooldownldevolutions,l ti control the speed and electrical load on theturbine generator, provide protection for the main turbine, maingenerator and main condenser.

A BOILING WATER REACTOR WITHOUTEHC PRESSURE CONTROLWith the reactor operating stable at 100% power: A small reduction in main turbine load results in; A rise in reactor pressure which results in; A reduction in core voids which results in; A rise in reactor power which results in; A rise in reactor pressure which results in; A reduction in core voids which results in; A rise in reactor power which results in; Etcetera, etcetera, etcetera

BOILING WATER REACTORPRESSURE CONTROLFor this reason pressure control in a BWR slavesthe turbine to the reactorTo reduce turbine load, you must FIRST reducereactor power which results in; A reduction in reactor steam pressure whichresults in; Lower steam pressure sensed at the turbinewhich results in; The EHC regulator closing the turbine controlvalves to restore pressure which results in; A turbine load reduction and stabilized pressure.

EHC PressureSensingEHC PressureControlFigure 3.2-6

Figure 3.2-1

Figure 3.2-1c

Figure 3.2-1

Figure 3.2-1d

Figure 3.2-1

Figure 3.2-1a

Figure 3.2-2

Figure 3.2-1

Figure 3.2-1b

Figure 3.2-4

Figure 3.2-5

TABLE 3.2-1 Turbine Trip ConditionsTripReactor Vessel HighLevelEHC Fluid HeaderPressure LowThrust Bearing WearSetpoint and Reason56.5"An excessively high water level could result inmoisture carry over to the turbine resulting in blade erosion ordamage. 1100 psig Loss of EHC oil pressure would indicate apotential for no control since this is the hydraulic source forvalve actuation. 35 milsIndicates a potential misalignment between thediaphragms and buckets which could result in mechanicaldamage to the turbine.MechanicalOverspeed TripBackup ElectricalOverspeed Trip110/112%Indicates potential turbine damage due toexcessive turbine speed and the resultant forces andmisalignment.Exhaust Hood HighTemperature225ºFExcessive temperatures would result in thermalstress, damage to exhaust hood or potential misalignment. 13 psig or 95 ºCIndicates operation of thegenerator under abnormal conditions. To prevent damage toStator Cooling Failurethe generator the turbine is tripped after a 70 second timedelay if generator amps are 5811. 105 psig @ 1300 RPMA turbine trip is required toLow Main Shaft Oilprevent bearing damage due to a loss of lubricating oil ifPump Pressureturbine speed is 1300 RPM.Low Bearing OilPressure8 psiglubricationPrevent turbine damage due to loss ofLoss of Both SpeedFeedback Channelsto EHC UnitTrips turbine because of potential overspeed condition ifturbine speed is 200 RPMLow CondenserVacuum22.5" HgIndicates a loss of heat sink and operation ofturbine at conditions for which it was not designedTurbine/GeneratorHigh Vibration10 milsvibrationAnticipates turbine damage due to excessive

60 rpm/min17990011800AVC rpm0 mw1017990At 33% reactort power930 psig105920 psig10920 psig7930 psig923 psig011033100 3301 33 32INITIAL TURBINE ROLL TO 1800 RPM01 32 33Figure 3.2-1

92027950923100100 100.1100100100105 0NORMAL STEADY STATE FULL POWER OPERATION 0Figure 3.2-1

53024920272194495092380100100 100.1801008010080100 0105 0REACTOR POWER REDUCTION FROM 100% TO 80% Figure 3.2-1

100BIG (-) 010035003500250018000 BIG (-)AVC18000100.1BIG (-)01800100.10TRIP THE TURBINE092609206920392692320100 105 0100.120 02020 0105 0 20TURBINE SHUTDOWN FROM 20% REACTOR POWER 20 0Figure 3.2-1

000000AVC000ASSUMES MAXIMUM DECAY HEAT0NOW TO COMMENCE THE COOLDOWN92210502920-19226.706.70007 6.7 6.7Raise to 7%PLANT COOLDOWN WITH THE BYPASS JACKFigure 3.2-1

000000AVC000ASSUMES MAXIMUM DECAY HEAT0NOW TO COMMENCE THE COOLDOWN922105072915920-14922236.706.723000 23 6.7 6.7 23PLANT COOLDOWN WITH PRESSURE SETFigure 3.2-1

Figure 3.2-3

SYSTEM INTERFACES Main Steam¾ EHC controls TSV, TCV, BPV, ISV, ICV positions¾ Main Steam provides EHC sensed pressure input Condensate/Feedwater¾ EHC causes extraction non-return valve closure on a turbine trip.¾ BPV’sPV s are interlocked closed at less than 7 inches mercury vacuum. Reactor Protection¾ RPS receives scram signals for TSV Closure and TCV Fast Closure fromEHC Turbine Building Closed Loop Cooling¾ TBCLC cools the EHC hydraulic oil.

OBJECTIVES1. Identify the purposes of the Electro HydraulicControl (EHC) system.2. Describe the significance of reactor pressurecontrol to BWR operation.3. Describe how the system accomplishes itspurposes.

OBJECTIVES4. Recognize the purpose of the following limiters: Load Set Load Limit Maximum Combined Flow

OBJECTIVES5. Recognize the purpose, function andoperation of the following EHC systemsubsystems: Pressure Control UnitSpeed Control UnitDesired Load Control UnitValve Control UnitHydraulic Power Unit

OBJECTIVES6. Given Figure 3.2-1, describe how the systemoperates to accomplish the following: NormalNl steadyt d statet t power operationsti Power maneuvering Plant shutdown and cooldown

OBJECTIVES7. Describe how the EHC system interrelateswith the following systems: MainMi StSteamCondensate and FeedwaterReactor ProtectionTurbine Building Closed Loop Cooling Water

The purposes of the EHC System are to: provide normal reactor pressure control by controlling steam flow consistent with reactor power control reactor pressure during startup, heatup, andld ltid cooldown evolutions, control the speed and electrical load on the turbine g