出典:Wiktionary
出典:『Wiktionary』 (2025/12/05 21:36 UTC 版)
heavy water (uncountable)
出典:『Wiktionary』 (2025/08/19 04:01 UTC 版)
出典:Wikipedia
出典:『Wikipedia』 (2011/07/23 00:47 UTC 版)
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched (in ordinary water, the deuterium-to-hydrogen ratio is about 156 parts per million). Pure heavy water is not radioactive. It is about 11% denser than water, but otherwise, is physically and chemically similar. However, the difference (especially the biological properties) is larger than in most other isotope-substituted compounds because deuterium is unique among heavy stable isotopes in being twice as heavy as the lightest isotope. This difference increases the strength of water's hydrogen-oxygen bond, and this in turn is enough to cause differences that are important to some biochemical reactions.