3710 Reactor Coolant System

Primary Functions of The Reactor Coolant System

• Removes heat generated in fuel by fission

• Transfers Heat through the steam generators

• Provides barrier against fission products

Secondary Functions of Reactor Coolant system

• Slows neutrons increasing fission probability

• Neutron reflection'

• Carries dissolved boric acid controlling reactivity

• Decay heat removal

Reactor Vessel

• Houses core and fuel assemblies, where fission happens

• Directs pressurized coolant through core then transfers to steam generators

Reactor Coolant Pumps

• Circulate coolant through reactor vessel and loops to transfer heat to steam generators and maintain flow

• Maintains DNR above 1.3

Steam Generators

• Produces steam to drive turbine

• Transfer heat from coolant to water system (keeps systems separate)

Pressurizer

• Maintains system pressure to prevent boiling

Accumulators

• Store borated water under pressure decrease

• Inject first

Safety Injection

• Provides emergency borated water to core during coolant loss or inadequate coolant

• on cold leg

RCS Loop Temperatures

• Measures temperature of coolant in hot leg and cold leg

• Helps operators monitor heat transfer, reactor conditions

RCS Loop Pressure Transmiters

• Measures coolant system pressure.

• Allows operators to monitor and prevent boiling

RCS Loop Flow Transmitters

• Monitor coolant flow rate through loops

Reactor Head Vent Isolation Valves

• Allow venting from reactor vessel

• Isolation valves close to prevent coolant loss

Reactor Vessel Leak-off

• Collects and monitors leakage from vessel seals

• helps detect leaks or boundary issues

RCS Level

• Monitors coolant inventory ensuring adequate fuel cooling

RCS Coolant Drain Tank

• Allows coolant to drain and collect in a controlled way

Metal Impact Monitoring System

• Detects impact or vibration that indicates loose metallic objects

Functions of Reactor Coolant

• Heat transfer

• Core cooling

• Neutron Moderation

• Containment

Reactor coolant heat transfer

• Removes heat from fission in core to steam generators

Reactor Coolant Core cooling

• Maintains fuel temp and prevents overeating

Reactor coolant Neutron moderation

• Water slows neutrons to help sustain fission reaction

Reactor coolant Containments

• Pressure boundary keeping radioactive materials in primary system

RCS Sampling and Failed Fuel detection

• Hot legs used because just exited core

• valves open but automatically close for safety injection

Residual Heat Removal Pumps

• cool during shutdown

• Low-head injection

Vessel Head Venting importance

Three mile island