Yes, SUBMISSIONS is a Scrabble word!

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

Is it a valid word?

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

something (manuscripts or architectural plans and models or estimates or works of art of all genres etc.) submitted for the judgment of others (as in a competition)
the act of submitting; usually surrendering power to another
the condition of having submitted to control by someone or something else
the feeling of patient, submissive humbleness
a legal document summarizing an agreement between parties in a dispute to abide by the decision of an arbiter
an agreement between parties in a dispute to abide by the decision of an arbiter
(law) a contention presented by a lawyer to a judge or jury as part of the case he is arguing