Showing posts with label Gas Cooled Reactors. Show all posts
Showing posts with label Gas Cooled Reactors. Show all posts

Types of Nuclear Reactor Power Plants

There are many concepts for the nuclear reactors, however, we will discuss few of following types of power plants that have been developed commercially.

Pressurized Water Reactor (PWR) Power Plant :

Pressurized Water Reactor uses water or heavy water as both the coolant as well as moderator. It uses enriched uranium as fuel. Water in the reactor absorbs the heat generated and converts it into steam. This steam generated is used for thermal power plant to drive its turbine and produce energy.

Boiled Water Reactor (BWR) Power Plant :

Boiled water reactor uses water as both coolant as well as moderator. It uses enriched uranium as fuel. In this reactor, water is directly converted into saturated steam. This steam is supplied to the steam turbine in conventional power plant and electrical energy is produced.

CANDU Reactor Power Plant :

CANDU stands for Canadian Deutorium Uranium reactor. It uses pressurized heavy water as moderator and primary coolant. Fuel used is natural uranium.
  For more details see - CANDU Reactor Power Plant

Gas Cooled Reactors (GCR) Power Plant :

These type of reactors uses gas as coolant and graphite as moderator. The advantage of using gas as coolant is that it is safe, easy to handle and it can be heated up to any temperature without change of phase at any pressure.
For more details see - Gas Cooled Reactor (GCR) Power Plants

Sodium Graphite Reactor (SGR) Power Plant :

This power plant uses graphite as moderator and sodium as coolant. Here, sodium is used as primary coolant and sodium potassium (NaK) is used as secondary coolant.

Fast Breeder Reactor (FBR) Power Plant :

In this reactor, moderator is not used. The primary fuel U-235 is surrounded by a blanket of fertile material. Fertile material like U-238 is kept there. Here, fast speed electrons are absorbed by U-238 which produces Pu-239.
  For more details see - Fast Breeder Reactor (FBR) Power Plant
   

Gas Cooled Reactors (GCR) Power Plant

A gas cooled reactor was first developed in U.K. which uses C02 as coolant instead of water and graphite as moderator. It is also called as Gas Cooled Graphite Moderated (GCGM) reactor. The basic diagram of gas cooled reactor power plant is shown in figure,
Gas Cooled Reactor Power plant | enggarena.net
Gas Cooled Reactor Power Plant
It uses natural Uranium as fuel. The coolant pressure is about 7 bar and temperature about 336 degree Celsius.
There was another gas cooled reactor developed in U.S.A which uses helium as coolant and graphite as moderator. It is called high temperature gas cooled (HTGC) reactor. The pressure and temperature of the coolant are 15 bar to 30 bar and 800 degree Celsius respectively.
HTGCR may work up to a thermal efficiency of 40%.
The advantage of using gas as coolant as compared to water is that it is safe, easy to handle and most important it can be heated up to any temperature without change of phase at any pressure though the gas has low heat transfer properties as compared to water.
However, while working with gas ass coolant in the reactors, large rate of gas circulation is required which is supplied with the help of blowers for affecting the required rate of energy transfers.
Therefore, for driving the large number of blower, large amount of energy is required as compared to the power needed for running the feed water pumps in case water is used as coolant. Thus, it reduces the thermal efficiency of the plant as compared to water cooled or liquid cooled power plants.

Advantages of Gas Cooled Reactors :

1. It has no corrosion problems.
2. As mentioned earlier, gases are easy to  handle.
3. These can be operated at high temperatures.
4. Gases can be pressurized easily.
5. Graphite remains stable at high temperatures and radiation problems are minimum.

Disadvantages of Gas Cooled Reactors :

1. Fuels have to be operated at high temperatures.
2. If helium is used as in case of HTGC reactor, leakage is a major problem.
3. Gases have lower heat transfer coefficient thus it requires large heat exchangers.
4. Large amount of fuel loading is required.
5. More power is needed for coolant circulation compared to water cooled reactors.