Japan plans to release slowly into the ocean a large amount of water containing an extremely low concentration of tritium.

Many countries are shouting about this. Is it really dangerous, or is that irrational exaggeration? I can't be certain, but I think it is irrational.

Japan claims that other nuclear power plants in the region release larger amounts of tritium annually than this water would. Indeed, Wikipedia's article on Tritium lists nuclear facilities that release much larger amounts of tritium, totaling almost 100 times what the Fukushima storage tanks would release — and the list is not complete.

It is clear that people are making an inordinate fuss about this tritium because it came from a major nuclear accident rather than from operating a reactor. However, the tritium itself is indistinguishable.

Nuclear reactors generate waste that is truly dangerous. That is the reason not to build more nuclear reactors — that and the danger that enemies will bomb them. In addition, they are so expensive and slow to build that they slow down decarbonization. Those are good reasons not to build more of them.

Likewise for the chemical industry — consider PFAs, which are toxic in very small amounts which are not radioactive and therefore don't decay at all.