The contamination from fukushima is detectable all over the planet just like all modern steel is detectably contaminated from 1960s nuclear testing[1]. It doesn't make it any kind of threat to the environment. We're talking about the same order of magnitude concentrations that are used in radiocarbon dating.
And the very dangerous isotopes you speak of, they have a very short half-life.
See also, the Oklo natural nuclear reactor complete with all the associated waste/contamination and the fact that it had little to no impact on the surrounding environment[2].
At the end of the day, there are 11 known and god knows how many unknown nuclear reactors dumped into the sea, and things have turned out pretty okay. One of them is even a popular dive site.
Again you're describing a sealed or mostly sealed, cold reactor, which is what most spills have been like. That is not what an accident would be like. It's a totally different scenario.
> And the very dangerous isotopes you speak of, they have a very short half-life.
Minutes, hours and days- easily long enough to kill local life outright. My point was that the local effects underwater would be far more disastrous than a similar accident on land, if there is life where the accident happens.
> See also, the Oklo natural nuclear reactor complete with all the associated waste/contamination and the fact that it had little to no impact on the surrounding environment[2].
It was active during the precambrian, and buried underground, which was again the exact assumption of yours that I had an issue with. You are really, fundamentally not understanding what I am saying- a nuclear accident is extremely different from disposal.
You make a sea reactor dump sound like China Syndrome. The fact that 11+ of them happened with no significant problems makes it pretty clear that you're exaggerating.
Microplastics and plastics in the ocean are a far more serious and far more tangible concern than a hypothetically hijacked ship hypothetically dumping the core which hypothetically turns into powder form.
Absolutely not. What you're saying is true for nuclear disposal- if you bury nuclear waste under the ocean floor there are no currents and no water table to disturb it, unlike on land where coolant water will rush towards drinking water, smoke does not diffuse evenly, and sediment does not naturally bury heavy isotopes.
It is absolutely not true for an accident. Radionuclides from Fukushima are measurable anywhere in the Pacific ocean. They're all over the planet. That's key though, because such even distribution means that even very dangerous isotopes are very quickly reduced to safe concentrations, or at least lower than background radiation.
On the other hand it is extremely difficult or impossible to save a priority environment if there is a real disaster. Convection will be driving far more radioactive material into the area than a land accident. You're not gonna ever have a meltdown (they already basically don't happen on land), but even a relatively small breach would have the potential to kill an entire area. Over most of the ocean that might be fine, but spawning areas or corals would be huge losses.