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Lecture 17

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Condenser CoolingWater System

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Condenser Cooling Water (CCW)System Requirements

Condenser maintains very low absolutepressure (near vacuum) through condensationprocess of steam (around 25200 times ofvolume reduction)

This allows roughly 35% more energyextraction than if the steam is left atatmospheric pressure

The effectiveness of the Condenser CoolingWater (CCW) causing condensation is

therefore an important requirement 2

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Condenser Cooling Water (CCW)System Requirements

While removing 70% of the reactors thermalpower into natural sources like river and sea,following are to be ensured:

Minimize the extent of thermal pollution in thereceiving water by limiting a temperature rise of5C within the shortest distance from the outfall

Minimize hot water recirculation at the intake CCW flow is to be adjusted to keep the

condensate at saturation temperature as

subcooling would reduce thermal cycle 3

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Functions and Ratings of CCWSystem

The breakup of cooling water flowrequirement and heat load for a typical 220MWe NPP is:

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Equipment Flow required (m 3/hr) Heat load (K.cal/hr)

Main condenser 33230 4.452 x 10 8

Turbine oil cooler 550 1.06 x 10 6

Boiler blow down cooler 90 0.9 x 10 6

Air extraction unit 108 0.4 x 10 6

Total CCW flow 33993

*Other NPP systems 2401 8.775 x10 6

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Functions and Ratings of CCWSystem

Number of CCW pumps 3 Pump head 25.50 mWC Shut-off head 42 mWC

Type Mixed flow vertical turbinebowl assembly pull outtype

Capacity 11650 m 3/hr Motor rating 1100 KW

CCW tunnels 3000mm (W) x2500mm (D) based on 1.3m/sec design velocity 5

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Functions and Ratings of CCWSystem

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Simplified Condenser Cooling Water (CCW) Systems

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CCW Pumps

These are high flow pumps with low dischargehead

They have a mixed flow characteristic Generally, started with discharge valve, part

open to limit startup current

Butterfly valve in pump discharge is kept fullopen, when the pump is operating Pump bearings are rubber lined and cooled by

clean water

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A View of Water Intake System

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Stop Gate

Trash Rake

Dual Flow Travelling

Water Screen

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Travelling Water Screen

Travelling water screens are provided at pumpsuction to filter CCW water continuously

This removes particles of over half inch The screen has rotating buckets which are

cleaned by water jet

Screen Dp is monitored continuously and italarms when it exceeds the preset value

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Travelling Water Screen

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Travelling Water Screen

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Operational Limitations andProblems in CCW System

The requirement about minimizing thermalpollution in the receiving water by limiting atemperature rise of 5C within the shortestdistance from the outfall is a limitation

This is because warmer station affluent canaffect local aquatic life, promoting growth ofsome species and endagering others

So limits are imposed on cooling waterteperature rise (T) and affluent temperature

(TE) 12

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Water Hammer Prevention

The very large CCW flow rate causesenoromous kinetic energy of the flowingwater

This promotes severe water hammer duringCCW pump startup, shutdown and trips

Following general operating practices to beused for water hammer prevention:

Sufficient time delay before the next pump isstarted

Proper positioning and slow opening/closing of 13