Yes, CIRCULATION is a Scrabble word!

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

Is it a valid word?

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

the dissemination of copies of periodicals (as newspapers or magazines)
movement through a circuit; especially the movement of blood through the heart and blood vessels
(library science) the count of books that are loaned by a library over a specified period
number of copies of a newspaper or magazine that are sold
free movement or passage (as of cytoplasm within a cell or sap through a plant)
the spread or transmission of something (as news or money) to a wider group or area