Reactor Classification

1. Nuclear reactors are classified by six principles.

2. They are: by the energy level of neutrons, by nuclear fuel, by purpose, by the arrangement of fuel and moderator, by the moderator used, by the coolant used.

3. By the energy level of neutrons, reactors are subdivided into fast, intermediate and thermal.

4. By nuclear fuel reactors are classified into natural uranium (with 0.7 % U235), slightly enriched U (with 1 – 2 % U235), highly enriched U (with 90 % U235), Pu239, U233.

5. By purpose there are power, research, prototype and production reactors.

6. By arrangement of fuel and moderator reactors are heterogeneous or homogeneous.

7. By the moderator used reactors are classified into heavy-water-moderated, light- water-moderated, graphite-moderated and beryllium-moderated.

8. By the coolant used reactors are divided into gas-cooled, organic-cooled, liquid metal-cooled and water-cooled.

Boiling-Water Reactor

1. A boiling-water reactor is that in which coolant boils in the reactor core to produce steam.

2. The steam is led directly to the turbine.

3. The heat exchanger is eliminated here.

4. The construction of a BWR is simpler and less expensive.

5. The high pressure is also eliminated, so the reactor doesn’t need a very heavy and strong construction.

6. The coolant remains longer in contact with fuel elements.

7. That is why water is a more effective coolant.

8. Pumps are eliminated because of natural coolant circulation.

9. The BWR uses a low cost fuel like natural or slightly enriched uranium.

10. A disadvantage is that the steam is radioactive and this results in corrosion and shielding problems.