Yes, LOOP is a Scrabble word!

Letter values in Scrabble US: L 1, O 1, O 1, P 3.

Is it a valid word?

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

fastener consisting of a metal ring for lining a small hole to permit the attachment of cords or lines
anything with a round or oval shape (formed by a curve that is closed and does not intersect itself)
(computer science) a single execution of a set of instructions that are to be repeated
an inner circle of advisors (especially under President Reagan)
the basic pattern of the human fingerprint
a computer program that performs a series of instructions repeatedly until some specified condition is satisfied
the topology of a network whose components are serially connected in such a way that the last component is connected to the first component
an intrauterine device in the shape of a loop
a complete electrical circuit around which current flows or a signal circulates
a flight maneuver; aircraft flies a complete circle in the vertical plane

Also: loop topology, closed circuit, loop-the-loop.