The radiation is intense but manageable. Its important to follow all that the Drs. suggest you to do. I trie dot just think of it as the magic medicine doing its work to kill off the evil cancer cells that were stray arround my body. My neck was bured after awhile and I felt tired for abotu 2 months afterwards- but Iw as out functioning in the world pretty much the whole time. I had some days where i didn't feel so good. It takes awhiel to recover but it didn't completely wipe me out. I made myself go on walks to museums shopping weekend road trip etc and even golf in the begining before ethe effects got too tough.
I'd say there was a bout 3 weeks when it was at its worst and then I just started to get better and better everyday and that was exciting.
Good luck and I'm sorry that your Dad and family are going through this. Just keep him distracted and busy and well hydrated and nourished and it won't be so bad.
LOVE Kate