As an example: there is a very long lived radioisotope of iodine that occurs in fission products, iodine-129, with a half life of 15 million years. The radioac

As an example: there is a very long lived radioisotope of iodine that occurs in fission products, iodine-129, with a half life of 15 million years. The radioactivity of this isotope is so low that, as I understand it, one could replace every iodine atom in your body with this isotope and you'd still be okay. This would imply it's fine to dispose of this isotope by just dissolving it into the ocean. The ocean's total iodine is about 10^11 tons, so a disposal rate of ~10^4 tons/year would eventually (in ~a half life) make the ocean's iodine mostly I-129 (conservatively, assuming no exchange of iodine is occurring between the ocean and external reservoirs of the element.) This production rate is what would obtain in a totally nuclear powered world at today's primary energy consumption rate.