Yes, HULL is a Scrabble word!

Letter values in Scrabble US: H 4, U 1, L 1, L 1.

Is it a valid word?

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

dry outer covering of a fruit or seed or nut
persistent enlarged calyx at base of e.g. a strawberry or raspberry
United States naval officer who commanded the `Constitution' during the War of 1812 and won a series of brilliant victories against the British (1773-1843)
United States diplomat who did the groundwork for creating the United Nations (1871-1955)
a large fishing port in northeastern England
the frame or body of ship

Also: isaac hull, cordell hull, kingston-upon hull.