Er, no. A Solar Neutrino Unit is defined by the detector medium, being one measured solar neutrino interaction per 1036 atoms in the "fiducial volume" (sensitive part) of the detector. For a chlorine-based experiment, you measure something like 2 SNU; for a gallium-based experiment, you measure more like 80 SNU. I'm not sure about SNO's SNUs.
It would probably be close to that of H2O, assuming that the crystalline detector form doesn't affect the interaction cross-section that much.
OBTW, it's spelled snow.
(evil grin...)