I think meaningless is a little strong. We talk about CO2 emissions, even though the air contains CO2. My understanding would be more radioactive than ambient radiation, or something along those lines.
I do agree that seeing some actual numbers would be helpful (eg: types and amount (estimated) of isotopes).
The total increase in CO2 levels over the last couple hundred years is about 30%, from 280 PPM to around 400 PPM.
By contrast, the total increase in the ocean's radioactivity from Fukushima is about 0.000002%, give or take a zero. While "trillions of Bq" sounds bad, and probably isn't good, the oceans contain something like 14,000 exaBq worth of Potassium-40 alone.
The problem with radioactive releases is more about concentrating it. There's sort of an anti-goldilocks situation. If a radioactive release doesn't spread very well at all, that's kind of OK. The radioactivity at the point of release is extremely dangerous, but hey, it is well contained and you can clean it up. If the radioactivity spreads extremely well, that's kind of OK too. It freaks people out, but realistically if you dilute radioactive materials enough they stop being dangerous. You're pissing in the ocean.
But if the radioactive material spreads JUST RIGHT, you can contaminate too large of an area to clean up while still leaving the radiation levels high enough to be dangerous.
I do agree that seeing some actual numbers would be helpful (eg: types and amount (estimated) of isotopes).