[inflatableDodo]

Now this is a wild guess on my part, not being a nuclear engineer and all, but I reckon that the foot is probably not just as lethal now it is inside this 'New Safe Confinement' thingy, unless they have gone and named it really, really badly.

[stephen_g]

The elephant's foot is quite deep under the reactor in a lower level of the complex. So I don't think it specifically is any more or less safe since you have to go to a lot of effort to get near enough for it to hurt you.

The New Safe Confinement has a different purpose - to stop radioactive dust and debris from the reactor itself (a bit higher up) from spreading into the nearby area and being spread by the wind in case the hastily constructed original containment structure collapses (they are going to remove that old structure now the NSC is finished so that doesn't happen, I believe).

[smittywerben]

This matches my understanding. It's been a few years since I was into this stuff so bear with me.

The NSC is so we can dismantle the Sarcophagus (the old containment structure). The fear is a explosion caused by the collapsing Sarcophagus (or perhaps there is another structural concern) might let the Elephants Foot reach the waterbed underneath the empty man-made cooling reservoir.

Here is a cross-section[0] of reactor 4 that shows the Elephants Foot (corium) at the bottom. I wish it'd show how far deep until water. I can't find information as to whether water even exists, or if this was just speculation (but Pripyat is swampy/marshy).

[0] https://i.imgur.com/qozfDP1.png

[mirimir]

TFA does note:

> Born of human error, continually generating copious heat, the Elephant’s Foot is still melting into the base of the Chernobyl nuclear power plant. If it hits ground water, it could trigger another catastrophic explosion or leach radioactive material into the water nearby residents drink.

I had never heard that it was "still melting into the base of the Chernobyl nuclear power plant". Given that it's only 10% as radioactive as it was initially, that seems unlikely.

[stephen_g]

This article (from 2016, three years later than TFA) says it’s estimated to be ‘slightly higher than the ambient temperature’ - https://www.atlasobscura.com/articles/the-famous-photo-of-ch...

While it reaching groundwater was definitely a concern in the 80’s, I don’t think it’s actually moved significantly or is expected to in the future.

[mirimir]

Thanks. That's more or less what I expected.

"China Syndrome" was an influential film. But until Fukushima, I don't believe that we saw melted core "lava" reach groundwater.

[topspin]

Without guessing the mass cannot be "just as lethal" now as at any point in the past. Its lethality comes from decay of unstable isotopes. Radioactive decay has a half life so radiation inexorably falls with time and lethality necessarily falls with it.

[Retric]

That would be true if exactly one isotope decade into a stable isotope. With more complex decay chains etc that does not always apply.

Ex: A has a half life of 100 years and B has a half life of 10 years. If the sample starts at 100% A it will become more radioactive for the first few years until B reaches a steady state.

[Gibbon1]

The radiation is a bad thing. And the radioactive isotopes in the thing are also bad. Considering it's from what I've heard and what I expect, turning slowly to dust, staying away from it is a good idea.

[gargravarr]

Very. Which is why the NSC was built to isolate it for at least 100 years (presumably it will be reinforced regularly by successive generations). Nothing we can do except allow it to decay to safe levels over time.