The only thing that could explode are the magnets. As mentioned by Countto10, there is a huge amount of energy stored in these magnets. Superconducting magnets are used, they are cooled using liquid helium. Due to a problem with the cooling, it can happen that part of a wire suddenly makes a transition from the superconducting state to the normal state. The huge current that moves through the wires will then get dissipated at that spot, generating an enormous amount of heat which will cause the liquid helium to exceptionally rapidly boil, expand in volume by a factor of ~800, heat the remaining helium, boil it, and therefore cause the whole magnet to essentially explode.
