View source for Light water

[[Category:Done 2018-06-01]] 
[[File:watermol.png|thumb|400px|right|Figure 1. A regular water molecule.<ref>Wikimedia Commons. (June 18, 2015). ''Water Molecule 3D'' [Online]. Available: https://commons.wikimedia.org/wiki/File:Water_molecule_3D.svg#/media/File:Water_molecule_3D.svg</ref>]]

<onlyinclude>'''Light water''' is simply ordinary water that does not contain large amounts of [[deuterium]], making it distinct from [[heavy water]].<ref name="RE1">Ian Hore-Lacy. (June 18, 2015). Nuclear Energy in the 12st Century, 1st Ed. Burlington, MA, U.S.A: Elsevier Inc, 2006.</ref> Although this water does contain small numbers of heavy water [[molecule]]s, it isn't enough to make any significant changes in its properties.</onlyinclude> Light water plays an important role in the [[electricity generation|generation of electricity]] from [[nuclear energy]], as it can serve both as a [[moderator]] and a coolant to carry away the energy generated by [[nuclear fission]].  

==Use as a Moderator==
:: [[Neutron moderator|''main page'']]
In nuclear fission reactors, the [[neutron]]s must be slowed down to ensure an effective [[fission chain reaction]] occurs. This process of slowing neutrons down is known as [[moderation]], and the material that slows down these neutrons is known as a [[neutron moderator]]. Light water can be used as a moderator in certain reactors, mainly [[pressurized water reactor]]s and [[boiling water reactor]]s.<ref name="RE1"/> Light water can only work as a moderator in certain situations, as it absorbs too many neutrons to be used with [[uranium]] that is unenriched, so [[uranium enrichment]] is necessary to operate reactors that use light water as the moderator.<ref>HyperPhysics. (June 18, 2015). ''Light Water Nuclear Reactor'' [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/ligwat.html</ref> This increases the overall cost of the operation, but makes light water reactors cheaper to build.

The simplest of these light water reactors is the boiling water reactor. More than 80% of the world's nuclear power plants use these light water reactors, with light water as their moderator.<ref name="RE2"/> In light water reactors, there exists a thick-walled pressure vessel that contains the nuclear fuel and the moderator and coolant water circulates among the fuel rods to slow neutrons and carry away [[thermal energy]].<ref name="RE2">Richard Wolfson. (June 18, 2015). Energy, Environment, and Climate, 2nd ed. New York, NY, U.S.A: 2012.</ref> 

There are several safety benefits that come from using light water as a moderator. First, the loss of any coolant deprives the reactor of its moderator, stopping the nuclear chain reaction. However, [[radioactive decay]] still continues to produce energy.<ref name="RE2"/> As well, any increase in the temperature of the reactor causes the water to become less dense, reducing the level of moderation that the light water supplies and reducing the activity in the reactor. This means that if the reactivity increases too much, there will be less moderation to slow the nuclear reaction.

==References==
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