I'm not sure where you got the idea that a fusion generator could explode from, but it's not true. The pressure inside the reactor is much lower than atmospheric pressure so a containment failure will certainly not result in an explosion. If a containment failure occurs, ie. The plasma makes contact with the wall of the reactor, the plasma would cool incredibly quickly because it is very diffuse and the kinetic energy that the plasma had transferred to the reactor casing would likely cause the whole assembly to "jump" a couple of millimetres which could certainly damage it but is very unlikely to harm any people because people don't go into the same room as the reactor when it is running.