Notwithstanding your qualifications, this reply is a bit off the mark. The tritium in that vial is indeed no danger, the beta decay of the tritium won't get pa

Notwithstanding your qualifications, this reply is a bit off the mark. The tritium in that vial is indeed no danger, the beta decay of the tritium won't get past the vial itself. Tritium ingested is indeed a danger, however, because once in the body, the water molecules that carry the tritium can and will go anywhere in the body. Most will be excreted in the urine, but some will some will end up in cell nuclei, where their low energy beta decay can and does do real damage to DNA. Note that I am not arguing that the tritium releases proposed in Japan are dangerous. They are far below any theshold for risk that should concern us. But that's because the concentration is so low, not because ingested tritiated water isn't potentially dangerous.