I'm working on a small little project involving the Raspberry Pi 3 and the LSM9DS1 Breakout board from Adafruit. We plan to place the Pi and the sensor board in a high radiation environment (but protected by a lead box), and the kit will be contained within a vacuum. I was wondering what would be a good way to cool down the Pi? Due to the lead box, we're stuck using Ethernet, and we can't use a fan due to being in a vacuum. According to some other questions, the Pi's Ethernet controller can only go up to 70 degrees Celcius. Using pipes like a laptop CPU seems to be an obvious choice, but I'm not sure if this is necessarily the best way.
EDIT: Someone mentioned that it was a bad idea to place the Pi in a vacuum due to the capacitors. Capacitors in a vacuum have the potential of exploding. I can see that happening with electrolytic capacitors, but what about ceramic caps? Looking at the Pi 3, I don't see any electrolytic caps that could explode. Also, in this regard, wouldn't any computer in a vacuum be a bad idea?
Thinking about the question in context, I guess I'm not exactly familiar with the conditions of a vacuum. To me, a vacuum assumes little to no pressure with no air. So, if there's no air, the environment will get hot quickly as things heat up, but am I fundamentally wrong about what goes on in a vacuum? Also, would it help if the Pi were enclosed in a box or something so that it doesn't get subjected to the conditions of the vacuum out in the open?