Shelley,

It is normal. It's called lymphodemia (spelling). It is the lymph fluid looking for a place to escape. The normal channels or pathways have been fried by the radiation.

I had it too. Massage, massage, massage. The lymph needs to find new pathways and massage is the only way to "teach" it how to find them.
I thought I was doomed to have a puffy turkey waddle the rest of my life but it really worked.