The idea that bringing a few bars of plutonium next to each other for a photo could result in a criticality event is completely bogus.
The real issue of course, is that you want people at a facility that handles plutonium to adhere very strictly to procedures. If you don't freak out when they take some selfies, next day they'll do something else. And one day, one of these things will be stupid and lots of people will get hurt.
The demon core incident(s), the Cecil Kelley criticality incident, and others don't involve explosives. Just read through the wikipedia list[0], and you'll see that causes included dropping a tungsten brick, an unexpected pool of water, and a human torso all acting as neutron reflectors and causing unexpected criticality.
Like, dissolved plutonium solutions have to be one of the most wickedly, unexpectedly dangerous things out there, because pouring them from one container into another, stirring them vigorously, or standing too close to them can all cause them to go from "safe" to "deadly".
[0]: https://en.wikipedia.org/wiki/Criticality_accident#Known_inc...
The photo in this article shows a few small sticks of plutonium. They are not in contact with each other. They are not surrounded by neutron reflecting materials. The chance of criticality in that configuration was insignificant.
Of course, any journalist worth his salt will make it look like we very nearly avoided an Armageddon.
I stand by my statement: the danger in that situation was not the plutonium configuration itself, but the attitude towards safety of the workers. In that immediate instance the chance of a criticality excursion was close to nil, but if not reprimanded, those workers could have done something much more dangerous next time.
For context, modern warheads use 3kg, much less than the demon core, and the pit that you link to the guy holding is likely a hollow shell of plutonium that is then covered in steel or beryllium. The pit itself is usually ~5cm, but would be closer to 3cm if it were solid Pu.
Like, assuming that the sharpie in the controversial image is a normal one, each of the top row cylinders are approximately 6 inches long and 1 inch diameter cylinders, meaning that the top cylinders are each 1.5kg of Pu, so that image probably has like 10kg+ of Pu, almost double what was in the demon core and 3-4x what's in a modern warhead (and I think I'm generally being conservative in those estimates, so it could well be closer to 15kg!)
And modeling exactly where that point is is difficult, hence the rules and restrictions.
The reaction of those involved lends much more credence to the “stop being idiots and clean this up Homer” reading.
Yes, but that somewhere is an epsilon below the demon core. How do I know? All nuclear bombs have a core, that's more or less the size of the Demon Core. They don't go critical until they need to.
Here [1] is a photo of scientist holding a plutonium pit with nothing but gloved hands. He is smiling. He does not look like someone thinking that the likelihood of a criticality event is all that high.
Now take another look at the few sticks of plutonium in the photo. Draw your own conclusions.
[1] https://lajicarita.wordpress.com/2012/10/16/cmrr-is-no-more-...
https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of...
There are probably multiple facets to this story as the article alludes to: a government funded private lab raking in the big bucks and government trying to rein them in a bit with this violation in an overly punitive way. Rendering then useless so production goes elsewhere...