I did some experiments with reactors and Thermal Expansion a while back. Its do-able. One Aqueous Accumulator can supply up to 4 Glacial Percipitators with water and each Glacial Percipitator can automatically eject snowballs into IC2 Compressors. Percipitators generating ice blocks is too slow to be useful for reactor cooling unless you have an insane amount of them or a low yield reactor. The compressors need to be overclocked to keep up with the Percipitators and the demand of the reactor. However, the design isn't without its costs as the Compressors need a large chunk of eu to keep running so you're going to need some additional source of power, at least in the beginning, to stockpile ice.