Yes, CONTAINMENT is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, T 1, A 1, I 1, N 1, M 3, E 1, N 1, T 1.

Is it a valid word?

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

a policy of creating strategic alliances in order to check the expansion of a hostile power or ideology or to force it to negotiate peacefully
(physics) a system designed to prevent the accidental release of radioactive material from a reactor
the act of containing; keeping something from spreading