Yes, SIMULATIONS is a Scrabble word!

Letter values in Scrabble US: S 1, I 1, M 3, U 1, L 1, A 1, T 1, I 1, O 1, N 1, S 1.

Is it a valid word?

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

the act of imitating the behavior of some situation or some process by means of something suitably analogous (especially for the purpose of study or personnel training)
(computer science) the technique of representing the real world by a computer program
representation of something (sometimes on a smaller scale)
the act of giving a false appearance

Also: computer simulation.