Yes, ACTIVATOR is a Scrabble word!

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

Is it a valid word?

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

(biology) any agency bringing about activation; a molecule that increases the activity of an enzyme or a protein that increases the production of a gene product in DNA transcription