yes, we should be thinking in terms of that much heat.

although conversion of alpha exit beam is potentially very efficient, (> 80%), the overall system efficiency is close to 50% if i recall correctly from figures Eric gave.

So a reactor capable of 5 MW of useful work will probably generate 5 MW of waste heat as well; and if you can boost the system efficiency, then you can increase the useful work while holding the waste-heat about the same.