#moderator.inhibitor  any substance used to slow down neutrons in nuclear reactors
  supertype:  inhibitor  a substance that retards or stops an activity
  subtype:  heavy_water  water containing a substantial proportion of deuterium atoms, used in nuclear reactors
  part of:  nuclear_reactor__reactor  (physics) any of several kinds of apparatus that maintain and control a nuclear reaction for the production of energy or artificial elements

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