Yes, PURGATION is a Scrabble word!

Letter values in Scrabble US: P 3, U 1, R 1, G 2, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

purging the body by the use of a cathartic to stimulate evacuation of the bowels
a ceremonial cleansing from defilement or uncleanness by the performance of appropriate rites
the act of clearing yourself (or another) from some stigma or charge