Yes, REACTORS is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, A 1, C 3, T 1, O 1, R 1, S 1.

Is it a valid word?

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

an electrical device used to introduce reactance into a circuit
(physics) any of several kinds of apparatus that maintain and control a nuclear reaction for the production of energy or artificial elements

Also: nuclear reactor.