Power Plant Engineering

10.10.9 COOLANT CYCLES
The coolant while circulating through the reactor passages take up heat produced due to chain
reaction and transfer this heat to the feed water in three ways as follows :
(a) Direct Cycle. In this system coolant which is water leaves the reactor in the form of steam.
Boiling water reactor uses this system.
(b) Single Circuit System. In this system the coolant transfers the heat to the feed water in the
steam generator. This system is used in pressurized reactor.
(c) Double Circuit System. In this system two coolant are used. Primary coolant after circulating
through the reactor flows through the intermediate heat exchanger (IHX) and passes on its
hest to the secondary coolant which transfers its heat in the feed water in the steam generator.
This system is used in sodium graphite reactor and fast breeder reactor.
10.10.10 REACTOR CORE
Reactor core consists of fuel rods, moderator and space through which the coolant flows.

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NUCLEAR POWER PLANT
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10.11 CONSERVATION RATIO
It is defined as the ratio of number of secondary fuel atoms to the number of consumed primary
fuel atoms. A reactor with a conversion ratio above unity is known as a breeder reactor. Breeder reactor
produces more fissionable material than it consumes. If the fissionable material produced is equal to or
less than the consumed, the reactor is called converter reactor.
Reactor
Feed
Water
Steam
Reactor
Hot Coolant
Pump
Feed
Water
Steam
Generator
Steam
( )
a
( )
b
Reactor
Pump
Pump
Primary
Coolant
Secondary
Coolant
1
HX
Steam
Steam
Generator
Feed
Water