Recent news stories are suggesting that TEPCO is considering evaporating the large quantities of radioactive water held in thousands of tanks at Fukushima.
Disposing large volumes of highly tritiated water is a serious problem for TEPCO but its evaporation proposal is quite dangerous. It is based on several misconceptions.
First, evaporating this radioactive water will NOT isolate the radioactivity: all it would do is convert liquid tritiated water to tritiated water vapour which would be emitted to the air at Fukushima and result in high exposures to those downwind of the plumes.
Second, evaporation would make the problem worse as, contrary to what many people assume, aerial emissions are more hazardous than liquid discharges to sea. Briefly, this is because you can avoid drinking tritiated water and food to a large degree, but you can’t avoid breathing in tritiated water vapour or absorbing it through skin.
Third, tritium is not “relatively harmless” as alleged. This is a common misconception: in fact, tritium is a relatively dangerous nuclide. For example, its beta particle inside the body is more harmful than most X-rays and gamma rays. But that’s just one aspect: tritiated water vapour has several other dangerous properties, and organically bound tritium (ie attached to lipids, carbohydrates and proteins) inside us is even more dangerous. See “Tritium- risks not properly assessed” in http://www.ianfairlie.org/lectures/
TEPCO is facing a storage problem with its tanks on site now full, and no space to build more. But neither evaporating the tank contents nor discharging them to sea appears to be a solution.