It's in the TFA, there a photo of a fellow holding a small box thing that looks like a battery from a car or an old box torch.

That’s the one I meant. It’s the core, but in a box, which makes it look even more innocuous, like he is indeed just lugging a piece of industrial equipment around. There’s lots of photos of the actual (unboxed) cores online if you search.

On flight WiFi so searching was a hard but I did find it. Thanks!

I saw that but not a picture of the plutonium core which I thought the OP was referring to