[en]

Many installations in Europe and neighboring countries are allowed to reject iodine-131 in the air. From Nuclear power plants (nuclear power stations, nuclear fuel reprocessing plant, etc.) to medical field (isotope reactors, nuclear medicine, waste incinerators, etc.).

source : http://www.criirad.org/balises/CRIIRAD_170214%20_I131_Europe... (french)

[datenwolf]

> Many installations in Europe and neighboring countries are allowed to reject iodine-131 in the air.

Given the very short half-life of 131I being just 8 days and the daughter isotope 131Xe being stable this is a really weird policy.

There's no good reason to force nuclear installations to keep 131I in storage for, say, 80 days to dilute its activity down to 0.1%. Heck there's no good reason to release it it all.

The decay product is a noble gas, so you even get the separation chemistry for free. Iodine is a halogen so just let it react with some alkaline (pass it through some caustic solution) upon which is forms ionic bonds and turns into saline solution. As soon as the 131I decays into 131Xe it will recombine with an electron and gas out.

[VLM]

The term to google for is "Avogadro’s number"

A mole of some chemical is a cardinal number and its a gross simplification but a "handful of stuff" has about ten to the twenty forth molecules or atoms. All to less than one sig fig. The exact number doesn't matter because enough half lives to dilute that much stuff to being statistically unlikely to contain less than 1 molecule is very large indeed. So at some point, where the radioactive activity is lower than say, a banana, or the ore it was dug out of, or a granite countertop, you just dump it. It takes a lot of half lives to take a banana down to zero radioactivity...

Probably the accident is somebody dumped the wrong bucket. You're supposed to dump bucket #32525 which has been aging for 100 half lives but accidentally bucket #64256 got dumped which was fresh. Or they reused buckets and markings (whoops there's two buckets labeled #15415)