Odd storyline, but...eh. I can't really stop you from making it.
You could make the ring out of wood, cut it into segments, then set it up so that they're held together by pegs...if that explanation makes sense to you.
For the explosion itself, you could either go the classic route and use pyrotechnics (if allowed, of course) or have say, strings to pull the ring apart (the segments make it easier to fall apart either way) and use a movie editing program to slap an explosion on there.
Or you could just animate it.
And NZ-TK...that picture makes me want to animate a Halo / Star Wars crossover...if I had any animation skills..or software, for that matter. Heh.