In other words, how much does the temperature of the whole thing change when you put an ordinary amount of material in there and run a reaction, right. Well, what do you do?
Some of the suggestions include using molten lead as the coolant for the system, but the reactor would run at atemperature above 700 degrees C. when the material becomes corrosive.
The helium, which by then will have risen to about minus 15C, is pushed through a liquid nitrogen "boiler" to bring it back down to its runtemperature, before looping back into the pre-cooler.
As a consequence data centers are using an increasingly large amount of power both to run equipment and to keep the operating temperature of that equipment at appropriate levels (this has led to building many newer data centers next to hydro-electric and other inexpensive power sources as well as in colder climates).