Just 66 nuclear power plants satisfy the bulk of all the electrical energy need throughout the USA. Together, they produce about 1,000 GW of electricity a year. The complete electricity-generating ability in the world is around 3,500 GW a year. The main dangers from a nuclear reactor are a meltdown of the core and the dispersion of radioactivity when coolant is missing, and the question how to store spent fuel. Nuclear contamination is very dangerous but is actually extremely rare, and when it happens, these accidents are always extremely well publicized.
19.9% of net generation is nuclear. Fission of uranium heats water to produce steam which rotates a turbine. In the nuclear core, material (a moderator, usually water or graphite) can be inserted between the radioactive matter that slows down the fission and cools the reactor. If water is used as that material, the reactor is called a light water reactor. Such a reactor has a 10-mile emergency planning zone. The two types of reactor processes in use are:
- Pressurized water reactor (PWR). Heat is removed from the reactor by water flowing in a closed pressurized loop, and then transferred to a second water loop at lower pressure. This loop will boil and produce steam. No radioactivity ever leaves the reactor (unlike in the BWR). PWR is also more thermally efficient than BWR. Most reactors in use today are PWR.
- Boiling water reactor (BWR). Water boils in the reactor itself, and the steam goes directly to the turbine generator. Small amounts of radioactivity are introduced into the pipes and turbine.
When nuclear fuel is used up, it can be stored or recycled, which often significantly minimizes the necessity to purchase new uranium and keeps operating cost of the plant down. The fuel that is stored is sealed in glass containers that can be dealt with in the two following ways:
- Storage of sealed containers in very deep volcanic seashore ditches where they slowly assimilate again with the core of the earth.
- Land storage (granite, volcanic tuff, salt, shale).
Storage of spent fuel poses the following two threats:
- Contamination on the surroundings.
- Abuse of the material for (illegal) weapons production.
Contrary to public opinion, nuclear fuel used in power plants can never sustain an explosive reaction like a nuclear bomb. This is so because a nuclear reactor contains only a very low concentration of fissionable substance (3.5-5% of U235). In contrast, a nuclear bomb concentrates in excess of 90% of fissionable components which can generate the runaway sequence effect that happens in a nuclear explosion.
Interestingly, nuclear power is a extremely handy and economic form of energy production. It is much cleaner than burning fossil fuel which emits carbon dioxide, along with SOx as well as NOx. A nuclear power plant will create no greenhouse gas. Furthermore, it costs very little to run a nuclear plant (the main cost is building it). In addition to green (totally free) energy, nuclear power plants provide the least expensive source of energy.