Now for the fun bit. First, glue the polonium disc to the steel one, and screw them into the hole you made in one of the bowls. Then pop the uranium ball in and bolt he two sides of the bowl together. Be careful you don’t catch your fingers.
Push the explosive down the tube with a broom handle. Glue the lithium disc to the flat nose of the uranium rod and ram it down into the explosive. Screw it into the globe – it will look just like a giant lollipop!
And that’s it, really. All you have to do is add the detonator and the timer, and you’re certain to get favourable marks. Alternatively, you could set it off behind the bike sheds. It will destroy everything for miles around and guarantee a day off school!