People have already submitted the Demon Core and a Los Alamos lab cart to put it on to the contest, but one thing is missing: the all-important screwdriver!

It's actually more like a modern screwdriver than one from the 1940s, as the handle cross-section is different, but it's more recognizable for that reason. It's in 1/12 scale, 25mm long. It's actually a bit chunky for its scale – the shaft would be over an inch thick – so that it can be printed on FDM printers as well as resin printers. 

Print one out and put it on your lab cart, next to your Demon Core, and you're all ready for a miniature criticality incident!