There are a number of different types of nuclear energy power plants, all with the same basic principal. The fundamental goal is to produce nuclear binding energy through fission. Heavy nucleus, from materials like uranium, create binding energy by breaking apart into smaller nuclei (McFarland et. al., 1994). Nuclear plants induce this fission in a number of different ways, but function with the same concepts in mind. Each power plant needs fuel – usually either uranium 235, 238 (aka either enriched or natural), or plutonium -, a moderator, and coolant (McFarland et. al., 1994). The moderator, which usually takes the form of either water or graphite, slows the down the moving neutrons. Fast neurons are produced during fission but must be slowed down for the process to sustain, so the moderating element is placed to “run into” the fast moving neurons, which then release kinetic energy and slow down(McFarland et. al., 1994). Water works well for this function because it can act as both moderator and coolant. Graphite is a much cheaper moderator, but is less stable. Each fuel, moderator, and coolant option have different efficiencies, stabilities, and costs, all of which are taken into account in the type of reactors that are used.
The three most common reactor types according to the World Nuclear Association are the Boiling Water Reactor (BWR), Pressurized Water Reactor (PWR), and the Pressurized Heavy Water Reactor (PHWR). The BWR uses water as both coolant and moderator, and enriched uranium as the fuel. It is the second most common reactor type. The water is heated through the fission, creating steam that turns the turbines of the plant. The PWR, which is the most common reactor, runs similarly to the BWR in that it also uses both water as coolant/moderator and enriched uranium as fuel. The PWR, however, increases the heat produced by increasing the pressure of the water, raising the boiling point. The PHWR uses heavy water as a moderator/coolant and natural uranium as a fuel. Natural uranium is less effective but is more common and easier to use (McFarland et. al., 1994). It is also one step farther away from being able to be used in nuclear weapons, which is an interesting addition to the nuclear energy discussion. Heavy water has a nucleus of Deuterium, which when combined with natural uranium, has a very efficient fission rate (McFarland et. al., 1994). It is very expensive because it is separated from normal water. It also creates a product known as tritium, which must be carefully taken care of, as it is radioactive.
These three types are not the only types of reactors, and each plant is considered by safety, efficiency, and cost (though not necessarily in that order). The nuclear energy industry is not internationally regulated, so each country balances these three aspects, as well as political and social implications before delving into the industry. There is a lot of contention of the best ways to weigh at each aspect accordingly, and the debate continues to be a hot topic. Two helpful sites to learn more about nuclear energy production and distribution around the world are the World Nuclear Association and the European Nuclear Society.
McFarland, E. L., Hunt, J. L., & Campbell, J. L. (1994). Energy, physics, & the environment. Winnipeg: Wuerz Publishing.