Yes, SENSATIONALISM is a Scrabble word!

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

Is it a valid word?

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

subject matter that is calculated to excite and please vulgar tastes
the journalistic use of subject matter that appeals to vulgar tastes
(philosophy) the ethical doctrine that feeling is the only criterion for what is good
(philosophy) the doctrine that knowledge derives from experience

Also: empiricist philosophy.