I think they’ve done the math on this and the impact will be negligible. The water is not very radioactive to begin with and it’s dumped into a huge ocean. People need to calm down and stop panicking every time they hear the r word.
This reminds me of how coal plants typically can’t be converted into nuclear plants because the coal plants are radioactive in excess of what’s legal for nuclear plants. You’re exposed to way less radiation if you live next to a nuclear plant than if you live next to a coal plant. The regulations are such a cluster fuck. This is why we can’t have nice things.
There’s also geoengineering, but that’s likely to have nasty side effects. Might still be better than nothing, though.