This is just a suggestion.
When you place a bucket of water in the Reactor (when its hot) the water will evaporate leaving only a empty bucket. I don't like how the bucket stays in the reactor after the water evaporates.
Making the Reactors spit out empty buckets would allow a automated Cooling system, which would involve BuildCraft.
Automated Cooling System:
1, A empty Bucket gets sent to the pump via build craft pipes.
2, The pump turns the Bucket into a Bucket of Water.
3, The Bucket of water gets sent to the Nuclear Reactor via BuildCraft pipes.
4, The Nuclear Reactor uses the Bucket of water to cool down, leaving a empty bucket.
5, The Empty Bucket gets spit out.
6, A obsidian pipe collects the Empty bucket.
7 Rinse and repeat.
For step 6, it would also be nice if the nuclear reactor would spit the buckets out in a chest that is placed beside the reactor. This way you could use a simple engine to extract the empty bucket.