Yes, REINCARNATION is a Scrabble word!

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

Is it a valid word?

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

embodiment in a new form (especially the reappearance or a person in another form)
a second or new birth
the Hindu or Buddhist doctrine that a person may be reborn successively into one of five classes of living beings (god or human or animal or hungry ghost or denizen of Hell) depending on the person's own actions