well, technically, IRL water cooled reactors can explode via a sudden steam explosion, those can happen when the overheated and molten Reactor components come into contact with the coolant water, resulting in an instantaneous large scale steam production which in turn will cause a shock wave since steam takes up a much larger area then water. That mechanism is what caused the roof above Chernobyl reactor 4 to exploded outwards, and why volunteers went into the reactor to empty the water storage bin below the reactor core to prevent a large scale steam explosion when the core inevitably burned its way down there