Yes, RADIATORS is a Scrabble word!

Letter values in Scrabble US: R 1, A 1, D 2, I 1, A 1, T 1, O 1, R 1, S 1.

Is it a valid word?

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

any object that radiates energy
heater consisting of a series of pipes for circulating steam or hot water to heat rooms or buildings
a mechanism consisting of a metal honeycomb through which hot fluids circulate; heat is transferred from the fluid through the honeycomb to the airstream that is created either by the motion of the vehicle or by a fan