Yes, RADIANCE is a Scrabble word!

Letter values in Scrabble US: R 1, A 1, D 2, I 1, A 1, N 1, C 3, E 1.

Is it a valid word?

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

the amount of electromagnetic radiation leaving or arriving at a point on a surface
the quality of being bright and sending out rays of light
an attractive combination of good health and happiness

Not playable in Scrabble US: REFULGENCY.