cool·ant
noun/ˈkuːlənt/
/ˈkuːlənt/
[countable, uncountable]- a liquid that is used for cooling an engine, a nuclear reactor, etc.
冷却剂，冷却介质（用于发动机、核反应堆等） Oxford Collocations DictionaryCoolant is used after these nouns:- reactor
Word Origin1930s: from cool, on the pattern of lubricant.