Moderator Definition in Physics

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By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on January 13, 2020

In physics, a moderator is a material that slows the speed of neutrons. It is also known as a neutron moderator. Using a moderator changes fast neutrons into thermal neutrons. Thermal neutrons increase the likelihood of interaction with another nucleus to initiate fission.

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By Anne Marie Helmenstine, Ph.D.

Moderator Examples

Water, graphite and heavy water are all commonly used moderators in nuclear reactors. The most common neutron moderator is "light water," which may be fresh water or may be deuterium-depleted water.

Sources

  • Kratz, Jens-Volker; Lieser, Karl Heinrich (2013). Nuclear and Radiochemistry: Fundamentals and Applications (3rd ed.). John Wiley & Sons. ISBN 9783527653355.
  • Stacey., Weston M. (2007). Nuclear Reactor Physics. Wiley-VCH. ISBN 3-527-40679-4.
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Helmenstine, Anne Marie, Ph.D. "Moderator Definition in Physics." ThoughtCo, Aug. 29, 2020, thoughtco.com/definition-of-moderator-605355. Helmenstine, Anne Marie, Ph.D. (2020, August 29). Moderator Definition in Physics. Retrieved from https://www.thoughtco.com/definition-of-moderator-605355 Helmenstine, Anne Marie, Ph.D. "Moderator Definition in Physics." ThoughtCo. https://www.thoughtco.com/definition-of-moderator-605355 (accessed April 19, 2024).