The nuclear power industry along with the reactor technology has been constantly developing for more than five decades now. Nuclear reactors can be classified based on their nuclear reaction, the moderator material used, generation of the reactor, fuel phase, fuel type, coolant used, etc. The fission nuclear reactors are mostly dealt with because the fusion reactors are still in the developing stages and the fission reactors are already being used for the past six decades.
Based on nuclear reaction
This type refers to the thermal (slow) reactors and the fast reactors based on the speed of neutrons. Thermal reactors are the most affordable and common as they use the natural and raw uranium; and the neutrons are decelerated from their natural speed when emitted from the broken atomic nuclei, and uses a moderating material in the process. The Fast reactors are very expensive that require more enriched fuel.
Based on moderator material
Thermal reactors (because of the presence of the moderating material), and Graphite, Normal water and Heavy water are also used as moderators. The moderating materials in the Graphite and the Heavy water reactors thermalize the neutrons and keep the natural uranium intact without any enrichment.
Based on generation
Generation I reactors were the first prototype reactors, Generation II used standard designs till 50s, Generation III were more modern, lightweighted, more efficient and were used till late 90s, the latest i.e. Generation IV reactors targeting on economical and minimal waste, are still in the research and development stage which may officially work until late 2020s.
Based on fuel phase and fuel type
It is Solid, Liquid or Gas reactor where Solid is most typical. The fuel type reactors also come with fuel phase- uranium or thorium, which are available in abundant quantities on the land.
Based on use
They are power plants, breeder reactors (the production of nuclear fuel), research reactors, etc.
Though the heat from nuclear reactors is used to generate approximately about 16% of the world’s electricity and have been used on satellites and act as power sources for aircraft, rockets and locomotives, what concerns the eco-biologists is how much this heat emitted is safe for the global citizens?
Realistically speaking, the radioactive waste emitted from these reactors carry risks for centuries or longer, as using this material cannot be completely done in a safe and secured manner; and the powerful potential for weaponry and environmental damage simply overshadows the nuclear energy benefits. It is more of a debate as there are varied opinions on this issue with global warming effects already becoming apparent and the alternative solutions to deal with it by other energy sources and their consequences are also heating up the whole thing, in the current scenario. The biggest advantage with nuclear energy of course is the production of vast amount of electricity with only a little amount of material, but the benefits look more restricted. A simple malfunction at the reactor or during the fission process can have devastating consequences, for instance Three Mile Island in US and Chernobyl in Russia in the past. Even a small amount of nuclear waste can have a huge impact on the surroundings for thousand of years or more because they are highly radioactive at first and slowly the radioactivity decreases with time taking even 500 years or more. Completely securing these reactors is not possible and the nuclear power generation may not be friendly to the environment with the risks it possesses unlike other renewable energy resources.
