Yes, EXPAND is a Scrabble word!

Letter values in Scrabble US: E 1, X 8, P 3, A 1, N 1, D 2.

Is it a valid word?

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

extend in one or more directions
become larger in size or volume or quantity
make bigger or wider in size, volume, or quantity
grow vigorously
exaggerate or make bigger
add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing
expand the influence of

Also: spread out, blow up, flesh out.