Fusion reactors are pretty non-explodey. Really all they can do is spring a leak, then fill with air and extinguish the plasma. Maybe if you quench the magnets

Fusion reactors are pretty non-explodey. Really all they can do is spring a leak, then fill with air and extinguish the plasma. Maybe if you quench the magnets hard enough you might get something dramatic like leaking a gram of tritium.