Yes, TRADITIONALISM is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, A 1, D 2, I 1, T 1, I 1, O 1, N 1, A 1, L 1, I 1, S 1, M 3.

Is it a valid word?

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

strict adherence to traditional methods or teachings
adherence to tradition (especially in cultural or religious matters)
the doctrine that all knowledge was originally derived by divine revelation and that it is transmitted by traditions

Not playable in Scrabble US: TRADITIONALITY.