In the nuclear power plant reactor is similar to the steam power plant furnace. In the reactor the heat is liberated because of the nuclear fission. The fuel present in the system must be circulated to provide cooling effort for the reactor core. The reactor leaves the hot coolant at the top and from that it flows through the tubes and then enters into the boiler (steam generator). From the boiler it passes through the feed water. The produced steam is delivered over the turbine; later work is done by expansion of steam in the turbine. The steam leaves from the turbine and then flows into the condenser. The pumps are provided to preserve the condensate, flow of coolant and feed water.
Different types of reactors
- Boiling water reactor
- Pressurised water reactor
- Fast Breeder reactor
Boiling water reactor
In short cut the boiling water reactor is known as BWR. The boiling water reactor is one of the types of light water nuclear reactor which is used for the generation of power. This method is the most common type for generating the electricity generator nuclear reactor after the PWR (Pressurized water reactor) which is another type of light water nuclear reactor. The difference between the boiler water reactor and pressurised water reactor is, it heats the water with the help of the reactor core and then the water turns into steam, with the help of the steam the turbine must be driven. In case of the pressurized water reactor also, the water is heated by the reactor core but it does not boil. So the heat transfer takes place between the hot water and the low pressure water, where it converts into the steam and pushes the turbine.
Components present in the system:
- Control system
- Condensate and feed water
- Steam turbine
- Reactor core
- Safety system
- Refuelling system
Advantages of Boiling water reactor:
- The reactor vessels and components are working at low pressure and that is nearly 70 to 75 bars
- Compare to the pressurised water reactor pressure vessel has less irradiation and not brittle
- The boiler water reactor operates at low nuclear fuel temperature.
- Due to no pressurizer vessel and no steam generators the fewer components have an external recirculation loop, if there is no piping it is eliminated.
- Rupturing causes the loss of coolant when compared with the pressurized water boiler.
- Minor risk in the damage of core like rapture is occurred. It happens mainly due to the large diameter pipes, welds and in other case no steam generator pipes.
- In emergency and normal condition the measurement of water in the pressure vessel is same. So it results in the relaxed and natural calculation of serious conditions.
- At low core power densities it can be operated by using the natural circulation without any forced flow.
- For natural circulation purpose only the boiler water reactor is designed so the recirculation pumps are entirely eliminated.
- In the boiler water reactor the boric acid is not used to control the fission burn up and it avoids the tritium production. It leads to possibility of corrosion in the piping and reactor vessel.
Disadvantages of Boiler water reactor:
- During the time of process, the 2 phases (steam and water) fluid flow in the higher portion of the core, so for calculations it is more complex along with the consumption of the nuclear fuel in the boiler water reactor.
- In this process, the reactor core it requires more instrumentation.
- In case of pressurized water reactor and higher pressure vessel the powers are similar with relatively the cost is also higher.
- In case of old models they use steam generator along with piping.
- With the short lived activation products the contamination is present in the turbine.
- This is due to the radiations released by the turbine during the working process shield and controls are arranged
- The radiation flux is emitted directly from the reactor core
- Compared to nitrogen the radiations emitted from the reactor core are less than nitrogen, where it releases high amount of radiations.
Click here to know more about: Pressurized Water Reactor and Fast Breeder Reactor, Advantages and Disadvantages