The Collaborative International Dictionary of English v.0.48:

Radiance \Ra"di*ance\ (r[=a]"d[i^]*ans), Radiancy \Ra"di*an*cy\
   (r[=a]"d[i^]*an*s[y^]), n.
   The quality of being radiant; brilliancy; effulgence; vivid
   brightness; as, the radiance of the sun.
   [1913 Webster]

         Girt with omnipotence, with radiance crowned. --Milton.
   [1913 Webster]

         What radiancy of glory,
         What light beyond compare !              --Neale.
   [1913 Webster]

   Syn: Luster; brilliancy; splendor; glare; glitter.
        [1913 Webster]

WordNet (r) 3.0 (2006):

radiance
    n 1: the amount of electromagnetic radiation leaving or arriving
         at a point on a surface [syn: radiance, glow,
         glowing]
    2: the quality of being bright and sending out rays of light
       [syn: radiance, radiancy, shine, effulgence,
       refulgence, refulgency]
    3: an attractive combination of good health and happiness; "the
       radiance of her countenance"

Moby Thesaurus II by Grady Ward, 1.0:

104 Moby Thesaurus words for "radiance":
   aura, blare, blaze, blaze of glory, blazing light, blinding light,
   blitheness, blithesomeness, bright light, brightness, brilliance,
   brilliancy, brilliant light, burst of light, charisma, cheer,
   cheerfulness, cheeriness, cheery vein, coruscation, dazzle,
   dazzling light, delight, diffusion, dispersion, effulgence,
   emanation, envelope, eupeptic mien, flamboyance, flood of light,
   fulgor, geniality, gladness, gladsomeness, glamour, glare,
   glaring light, gleam, gloriousness, glory, glow, good cheer,
   gorgeousness, halo, happiness, heavenliness, highlight,
   hopefulness, illumination, illustriousness, incandescence,
   irradiance, irradiancy, irradiation, joy, light, light source,
   luminosity, luminous energy, luminousness, luster, magic, mystique,
   nimbus, numinousness, optimism, phosphorescence, photosensitivity,
   pleasantness, pleasure, radiancy, radiant energy, radiant splendor,
   radiation, radius, ravishingness, ray, refulgence, refulgency,
   resplendence, resplendency, rosy expectation, sanguine humor,
   sanguineness, scattering, scintillation, shimmer, shine, sidelight,
   sparkle, splendidness, splendor, splendorousness, splendrousness,
   spoke, streaming light, sublimity, sunniness, twinkle,
   visible radiation, vividness, warmth, winsomeness