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Comment by nafizh | Hacker News Reader

So after 870 years, it begins to pollute the water?

10 half lives means it will have reduced radioactivity to

(1/2/2/2/2/2/2/2/2/2/1)*100 % of original or .19% of its original radioactivity. Also keep in mind radioactive decay is not even. The faster, thus more dangerous, particles inherently decay faster and will be even more degraded, I'm not going to do the math on it, but, probably another order of magnitude or three.

True but plutonium is pretty poisonous too. Luckily the ocean is very big

Source? Other than the radioactivity, plutonium isn’t any more poisonous than other heavy elements, afaik. And it’s not a lot of material.

I think the comment is referring to the heavy metal toxicity, which is presumed but poorly studied in humans.

Yeah but we’re talking about a small amount of material. There’s probably more lead in the electronics you use. Dumped in the ocean, it’s nothing.

> There’s probably more lead in the electronics you use.

Probably not, ever since RoHS in 2002 lead has all but disappeared from electronics. Even though it’s an EU law, most suppliers have just decided to only provide RoHS-compliant parts, and PCB manufacturers only have options for RoHS-compliant solder.

The amount of lead in an electronic is probably measured in grams, and only if the device was manufactured prior to 2005 or so.

> Luckily the ocean is very big

As is the planets atmosphere, which for the longest time served as a justification to pump it full with emissions, that now leave us with a run-away problem at a scale that's still difficult for most people to wrap their heads around.

That's a problem because we're still pumping out emissions. RTG losses have been a small number (under 5) accidents that have probably emitted in total under 10kg of material.

But RTG losses ain't the only emissions of pollutants into the oceans.

Fukushima is leaking into the Pacific to this day even with Tepco collecting vast amounts of it to store in tanks. The US is dumping the majority of its PFAS into the Atlantic completely untreated, large parts of the world use the oceans as their dumpster, for agricultural, industrial, plastic and all kinds of other waste, to such a degree that we are running out of great coral reefs but instead have great garbage patches.

Yet for the longest time we only worried about oil spills, which are also an still on-going issue in addition to all the aforementioned ones, old ones like the vast amounts of munitions dumped into it, which also includes chemical weapons [0] and possibly upcoming ones like deep-sea mining.

It's mind-boggling to me how we as a collective species can be so unbelievably short-sighted to only recognize these problems once they've already run so far away from us that any attempts at solving them are borderline impossible.

[0] https://www.smithsonianmag.com/science-nature/decaying-weapo...

Sure. But the question was about the environmental impact of RTGs, which is many orders of magnitude smaller than other problems.

There wasn't any question, there was the statement that plutonium couldn't be that harmful because "the ocean is very big".

Which is another version of "the solution to pollution is dilution", but that ignores that dilution doesn't scale indefinitely and if overdone can also lead to saturation.

There was absolutely a question.

morsch said: "The cask survived re-entry, as it was designed to do,[18] and no release of plutonium has been detected. The corrosion resistant materials of the capsule are expected to contain it for 10 half-lives (870 years).[19]"

nafizh asked: "So after 870 years, it begins to pollute the water?"

It was a question about the Apollo 13 SNAP-27 unit, which was spilled in a freak accident that is unlikely to be repeated.

After it decays, it's no longer plutonium; instead it's uranium-234. Uranium's heavy-metal toxicity is quite well-established, and uranium-234 is more radioactive than the natural isotopic mix, but at the low-single-digit-kilogram scale involved in the SNAP-27 RTG it's not a major concern.

The connection between half life and decay energy isn't so linear. Looking at a table of gamma ray energies [0] one can see that the lowest-energy distinct five have half lives in hours:

with the highest-energy distinct five in hours:

          12.8
          15.0
           3.48
           1.9
  6280920000    (717,000 years!)

However since the output power is the product of the activity and the decay energy it certainly follows a diminishing curve since fewer decays as time advances.

[0] https://application.wiley-vch.de/books/info/0-471-35633-6/to...

One RTG is nothing, a handful of whole nuclear reactors have been dumped into the ocean before (a few of the accidentally, and a few of the deliberately.)

Adding Fukashima and dozens of nuclear tests. It's like we tried to chemo the ocean for 30 years.

Ocean water already contains 4 billion tons of uranium: http://large.stanford.edu/courses/2010/ph240/gorin2/

And then we get Godzilla.

Most of it will have decayed into Uranium-234, which will pollute the water. If the container really contains it for that long. Fortunately the ocean is really big.

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