Yes, ACTIVE is a Scrabble word!

Letter values in Scrabble US: A 1, C 3, T 1, I 1, V 4, E 1.

Is it a valid word?

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

chemical agent capable of activity
the voice used to indicate that the grammatical subject of the verb is performing the action or causing the happening denoted by the verb
a person who is a participating member of an organization

tending to become more severe or wider in scope
engaged in or ready for military or naval operations
disposed to take action or effectuate change
taking part in an activity
characterized by energetic activity
exerting influence or producing a change or effect
full of activity or engaged in continuous activity
in operation
(of the sun) characterized by an increased occurrence of sunspots and flares and radio emissions
expressing that the subject of the sentence has the semantic function of actor: "Hemingway favors active constructions"
(used of verbs (e.g. `to run') and participial adjectives (e.g. `running' in `running water')) expressing action rather than a state of being
(of e.g. volcanos) capable of erupting
(of e.g. volcanos) erupting or liable to erupt
engaged in full-time work

Also: active agent, active voice, combat-ready.