While we're on the topic of explaining nuclear energy, you can find some recorded nuclear fission demonstrations on YouTube. I know many schools have blocked YouTube, but I hope it's still useful to some of you.
My favorite video comes from Touchstone Energy. While not recorded for scientific purposes, the sheer size of the demonstration is impressive. You'll have to ignore the sales pitch, but it's non-offensive and pretty short.
And, just for fun, here's another commercial video along the same lines.