Yes, EXPLOSION is a Scrabble word!

Letter values in Scrabble US: E 1, X 8, P 3, L 1, O 1, S 1, I 1, O 1, N 1.

Is it a valid word?

EXPLOSION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a violent release of energy caused by a chemical or nuclear reaction
the act of exploding or bursting
a sudden great increase
the noise caused by an explosion
the terminal forced release of pressure built up during the occlusive phase of a stop consonant
a sudden outburst
a golf shot from a bunker that typically moves sand as well as the golf ball