Removing Radiation from Water
Date: April 6, 2011
Radioactive Water: If you have radioactive water, and distill it, if the water was not radioactive but had a radioactive mineral dissolved in it, will the distilled water, minus that radioactive element, be radioactive or is there a chance the distilled water will be radiation free? Is there any surefire way for removing all radiation from water?
It depends on what the radioactive contaminant is, and it depends on
how the distillation is carried out. It also depends on your
standards for "radiation free."
Part of the problem is that radioactive waste usually contains many
different radioactive elements, each with unique chemical
properties. Most of the really bad actors, like cobalt, plutonium,
cesium, and strontium, do not form compounds with high
volatility. So they will not go into the vapor phase, and
theoretically will be left behind in the pot in a distillation. In
practice, however, distillation involves boiling, which produces
aerosols. Some of these may be carried into the
collector. Different ways of running the distillation can increase
or decrease the extent to which this happens.
In many cases, major proportions of the radioactive contaminants can
be removed by ion exchange or reverse osmosis. But what fraction of
residue is low enough?
Some contaminants, such as radon and iodine, will not necessarily be
removed by a simple distillation of the water. More complex
distillations can do better, but exactly what is best to do depends
on the specific situation.
Basically, distillation will probably remove a lot of the
radioactive contamination from water. Whether or not the distilled
water is safe to drink will depend on how much radioactivity is left
and what your standards of safety are. Do not forget that all of us
are daily exposed to ionizing radiation from natural and man-made
sources. Your distilled water will not be "radiation free." But
then again, water from a pristine mountain stream is not radiation
free either, and it would not have been even before humans
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
If you have "radioactive" water, it depends upon the amount and the source
of the radioactivity. This common candidates would be alpha particles (the
nucleus of a helium atom), beta particles (energetic electrons), gamma
radiation (high energy electromagnetic radiation) -- and mixtures of these.
An additional factor is the chemical form in which the radioactivity is
present. This could be numerous chemical elements with various radioactive
As well as various compounds. So you are looking at separating various
chemical species, with varying radioactivity. You can see that what starts
out to be an easy question, has a very complex answer. You cannot just
assume the radioactivity comes from some mineral that remains dissolved in
the distillation "pot".
In principle you could separate the radioactive mineral from the water, but
at a large energy cost. The heat of vaporization of water requires a lot of
energy, so even if the chemistry "works on paper" does not mean that it would
be feasible on a large scale. Believe me when I say that if a distillation
were so simple, it would have been tried a long time ago. It is not an easy
Click here to return to the Chemistry Archives
Update: June 2012