I have been thinking about external liquid cooling for reactor vents similar to a build-craft combustion engine.
A block that is able to be added to the outside of a reactor that directly drops or maintains the hull temperature of the reactor it is attached to using coolant such as ICE/Water/Coolant
Before anyone comes along with the "Coolant needs to be hot" line again, in a reactor you have
Reaction > Really hot coolant loop > Steam generation (Which gets sent off to turbines and cooled)
However if that steam generation loop is not sufficient to cool a reactor there are other things that are in place to help cool should the need arise. These coolant methods are not the closed loop that runs inside the reactor, and seeing as the reactor is completely enclosed (produces steam and has cooling vents) It is safe to assume it is not a 100% accurate to life simulation, thus allowing for external piped coolant to be used in order to maintain hull integrity.
I also know this description is stupidly oversimplified but I noticed you have plans for your freezer and reactor cooling and thought that idea might have legs.