Using Buildcraft and equivalent Exchange -- you can do the bucket autofill thing. Use an 'Evertide Amulet' which, when combined with an empty bucket, produces a water bucket (and does not use up the evertide amulet --- basically, unlimited water).
I have been thinking about doing a buildcraft system with the auto crafting table to do this -- but without being able to reliably get the empty bucket out of the nuclear reactor, I was going to use compressors to make ice and feed them in.