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Comment by kennend3 | Hacker News Reader

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kennend3·

> there’s no “critical mass” storage problem,

These accidental criticality accidents indicate otherwise:

https://en.wikipedia.org/wiki/Criticality_accident

Accidentally going "critical" is a very real risk, especially with plutonium and it allotropes

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All of those examples involve reactors, single cores, or fluid containers.

yes.. it seems a few people misunderstood the statement as "plutonium cant go critical" vs the correct interpretation "storing pits close to one another".

Those are only the confirmed criticality incidents -- there have been "near misses" by just plain idiocy in storing plutonium, including a US nightmare where they decided to gather a bunch of rods together to take a picture of them all in frame.

https://www.science.org/content/article/near-disaster-federa...

I think the main source of confusion is here is that the original author said "weapons", which about half of commentators have taken to mean weapons/warheads and half have taken to mean nuclear material of any variety.

Yeah that's a fair point -- it's unlikely for pits to ever achieve accidental criticality given their design and setting. Much less so for plutonium in general which you'd likely have to deal with anywhere you have a bunch of warheads hanging out.

From the article, "...or melted down and formed into the pit of a new weapon with a new geometry..." did make me consider the consequences of melting near-critical amounts of plutonium or uranium. Which certainly sounds exciting!

Presumably they do so within certain mass limits and geometries? Does the critical mass change in liquid form?

Almost certainly. It's just a probabilistic balance between neutrons in vs neutrons out, and between the neutron decay rate and density of the material changing it'd be unlikely for everything to balance out perfectly to keep the critical mass the same.

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