Not due to fission or a nuclear chain reaction. If the core overheats it can melt through its containment vessel and if it hits water that may have been pooled in the vessel due to a coolant leak and generates steam, it can cause a steam explosion.

BLEVE stands for "Boiling Liquid Expanding Vapor Explosion" which results from the rupturing of a vessel containing a pressurized liquid above it's boiling point.

In a 'meltdown', the nuclear fuel rods will overheat and melt, not explode. It is the build-up of pressure within the containment vessel that can cause an explosion.

Hyphema is caused by blunt, projectile, or explosion (about 4% of cases) injuries. These injuries cause a local blood vessel in the eye to tear, filling the front portion of the AC with blood.

the explosion = die Explosion.