I get alot of secretions from the back of my throat, near my palate, it's within the area that's being radiated, yoru mouth is naturally a moist place, as is your nasal area - it isn't alway a salivary gland spitting out fluids - though Brian maybe can tell you a little better, but you know whe you have to clear your throat and spit - it probably comes from the same place. I think its pretty normal.

Good luck - you will heal, you body just has it's own time table that's all.