In PWR, the water that cools the nuclear fuel at a higher pressure and doesn’t convert into steam. Because of the higher pressure, this primary water can reach higher temperatures and used to convert a secondary water supply into steam and from there to the steam turbine.
The main parts of the PWR are
Pressure vessel
Thermal shield
Fuel elements
Control rods
Reactor containment
Reactor pressuriser
The core inside the reactor vessel creates heat.
Pressurized water in the primary coolant carries the heat to the steam generator.
Inside the steam generator heat from the primary coolant loop vaporizes the water in a secondary loop producing steam.
The steam line directs the steam to the main turbine, causing it to turn the turbine generator, which produces electricity.
The unused steam is exhausted to the condenser, where it is condensed into water.
The resulting water is pumped out of the condenser with a series of pumps, reheated and pumped back to the steam generator.
The reactor's core contains fuel assemblies that are cooled by water circulated by using electrically powered pumps.
These pumps and other operating systems in the plant receive their power from the electrical grid. If offsite power is lost, emergency cooling water is supplied by other pumps, which can be powered by onsite diesel generators.
The moderators which are commonly used are ordinary water and heavy water.
Other safety systems such as the containment cooling system also need electric power. PWRs contain between 150-200 fuel assemblies Function of the moderator is to reduce the energy of neutrons evolved during fission in order to maintain the chain reaction.
Advantages :
Water used in reactor such as coolant, moderator and reflector is cheap and easily available.
There is a complete freedom to inspect and maintain the turbine, feed heaters and condenser.
Fission products remain contained in the reactor and are not circulated.
A small number of control rods is required. This reactor is compact and high density.
Always reduce the fuel cost.
Disadvantages :
Capital cost is high.
Thermodynamic efficiency is low.
Fuels suffers radiation damage, therefore its reprocessing is difficult
Fuel element fabrication is expensive.
Severe corrosion problem.
It is imperative to shutdown the reactor for fuel charging.
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