Why is “heavy water” used in nuclear energy, are not potable to drink, even it’s just 1 molecule more than H2O?
In: Chemistry
Heavy water does not have any more molecules of H20. A molecule of H20 is just the smallest possible unit of water. More molecules just means you have more water. Heavy water is water where the hydrogen atom has an extra neutron. It’s still water, because it’s 2 hydrogen atoms and an Oxygen atom, and the extra neutron doesn’t change the hydrogen chemically. It weights more though, because of the extra particle… so we call it heavy water.
It’s used in nuclear energy because it’s a good neutron moderator. A neutron that is moving very fast tend to not be absorbed well – you want slower neutrons, as they are more readily absorbed , which is what needs to happen for fission (and a chain reaction) to occur. Heavy water does a good job of [slowing down neutrons](https://en.wikipedia.org/wiki/Neutron_moderator) without absorbing them.
The heavy hydrogen in water inhibits cell division in mammals, so it’s toxic. But, you need drink a lot of heavy water for it to become a problem.
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