Yes, TRIODE is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, I 1, O 1, D 2, E 1.

Is it a valid word?

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

a thermionic vacuum tube having three electrodes; fluctuations of the charge on the grid control the flow from cathode to anode which makes amplification possible