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0 pointsAdamJacobMuller5y ago0 comments

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.

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thombat5y ago

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...

GekkePrutser5y ago

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

azernik5y ago

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.

freeflight5y ago

> 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.

azernik5y ago

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.

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garmaine5y ago

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

klodolph5y ago

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

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thombat5y ago

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...

GekkePrutser5y ago

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

azernik5y ago

freeflight5y ago

> Luckily the ocean is very big

azernik5y ago

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.

1 more reply

garmaine5y ago

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

klodolph5y ago

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

1 more reply

j / k navigate · click thread line to collapse