Yes, MELIORATIONS is a Scrabble word!

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

Is it a valid word?

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

the act of relieving ills and changing for the better
a condition superior to an earlier condition
the linguistic process in which over a period of time a word grows more positive in connotation or more elevated in meaning