Yes, INFERNOS is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, F 4, E 1, R 1, N 1, O 1, S 1.

Is it a valid word?

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

any place of pain and turmoil;
a very intense and uncontrolled fire
(Christianity) the abode of Satan and the forces of evil; where sinners suffer eternal punishment

Also: hell on earth, snake pit, the pits, infernal region, nether region.