Yes, PRIMARIES is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, I 1, M 3, A 1, R 1, I 1, E 1, S 1.

Is it a valid word?

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

a preliminary election where delegates or nominees are chosen
one of the main flight feathers projecting along the outer edge of a bird's wing
(astronomy) a celestial body (especially a star) relative to other objects in orbit around it
coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit

Also: primary election, primary feather, primary quill, primary coil, primary winding.