What is a melt-down and how can it occur?

Question

And is there any danger of a steam explosion if the reactor core becomes overheated?

Answer 1

Melt down is a process in which the core of the reactor melts due to enormous amount of heat liberated by fission reaction, this happens when there is no care taken on the reactor,

Yes of course there is some damage but not serious due to steam explosion, usually melting down of a reactor dont explode but cause fatal injuries who are near to the reactor...