For the mod Blueprint Sandboxes, it adds infinity chests. For whatever reason, I can select new infinity chest with warhead icons with names such as "Utility provided by the mod, 50Mt atomic warhead" with the description starting with "Utility provided by the mod, deploying: ..." I can also select a detonation titled "Unknown key: "item-name.detonation-atomic-15kt-2" down to ...0_1t... There's also 3 different 15kt detonation icons and 2 of 100kt, 1Mt and 5Mt.
Screenshot: https://ufile.io/t3onz1hq

Yes, those are all internal items used/produced by the mod.
The "utility" projectiles are used entirely for scripting, and are deliberately unobtainable - the infinity chest is to make sure of this - they are some form of ammo (cannon shells maybe), just because the scripts producing them always produces an item.
The multiple atomic detonations are for the different cores. These are used as markers to allow the nuclear tests.
I hadn't considered the mess they would all make in infinity chests, but they are all kind of necessary for bits of functionality in the mod.
I guess I should put all of this under the utilities category (or whatever the infinity chest and such are from).