Yes, ACTIVATE is a Scrabble word!

Letter values in Scrabble US: A 1, C 3, T 1, I 1, V 4, A 1, T 1, E 1.

Is it a valid word?

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

put in motion or move to act
make active or more active
make more adsorptive
aerate (sewage) so as to favor the growth of organisms that decompose organic matter
make (substances) radioactive

Also: set off, spark off, trigger off, touch off.