With the usual disclaimer that everyone is unique: my experience was that the first two weeks of radiation were a breeze. I had not trouble driving, going out to resturants, even exercising at the gym. I had not yet found OCF so I was in for a very rude awakening the remainder of my treatment.
PS. Ask your radiation oconologist what your total treatment dosage is. The standard measurement is GY, each of which is 100 Rads (old measurement). The typical aggressive treatment is 72 GY. More than that can be very problematic. You might also ask the average dose planned for each week. My first round jumped up tremendously the last two weeks.
Finally, the worst part of radiation is the time afterwards.