[tedk-42]

Explosion as in a nuclear one? Really isn't possible. The fissile material isn't pure enough.

I believe graphite rods are used as the safety to capture the neutrons in a nuclear fission reactor and effectively kill off the reaction.

Explosion as in Chernobyl level? That was basically water pressure.

[pfdietz]

Chernobyl had two explosions, a few seconds apart. The second, larger one was after most of the water had left the core. The reactor had a positive void coefficient, so losing water increased reactivity.

Of course these were prompt supercritical reactions in a moderated system, so they are not explosions in the sense of bombs, which are fast systems with neutron doubling times measured in fractions of a microsecond.