[gabriel34]

None of these examples were worst case scenario. How well does the ocean absorbs the ionizing radiation from a meltdown or some other extreme event? Would part of the ocean's water become radioactive and spread through currents? Are the oceans so voluminous that the effect would be only a minor increase in radiation levels?

[mpyne]

Well the mantle of the Earth (including its radioactive components that power plate tectonics) is literally pouring forth into the depths of the Atlantic Ocean (in the valleys of the mid-Atlantic Ridge) and that seems to have not caused noticeable calamities... which is because yes, the ocean really is that voluminous.

As it turns out the ocean is also really good at both shielding radiation (water is what the nuclear experts use in large amounts, after all) and diluting radioactive contaminants, if it came to that, until the radionuclides themselves decay away and become stable.

Additionally it's not as if radioactivity is infectious or permanent. If something is radioactive here and I move it over there, it can't be radioactive in both places, which is why dilution is so effective.

[stefantalpalaru]

http://en.wikipedia.org/wiki/Bioaccumulation

[mpyne]

You seem to imply that I haven't heard of this. Does this contradict anything I said and if so, how?

Before you answer, you might want to compare "biological half-life" with "radiological half-life" (as they are usually far different), and why the same issue of bioaccumulation has noted caused famine from hazardous materials that we know to have been dumped into the ocean in orders of magnitude much larger quantities. How many oil spills have fisheries survived in general?

[dalke]

The Fukushima Daiichi nuclear disaster gives a good approximation of what that would look like. "Pretty well", "yes, but well below what's considered safe limits", "yes, detectable but minor."