moderator

nuclear reactor

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In nuclear reactor: Coolants and moderators
A variety of substances, including light water, heavy water, air, carbon dioxide, helium, liquid sodium, liquid sodium-potassium alloy, and hydrocarbons (oils), have been used as coolants. Such substances are, in
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In nuclear reactor: Thermal, intermediate, and fast reactors
…reactor and are known as moderators. Since water and heavy water also can function as coolants, they perform a dual purpose in thermal reactors. (See below Coolants and moderators.)
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