Zoladex will give you dry orgasms (and for many men, no orgasms at all), so you can't tell the effect of the radiotherapy until you've come off hormone therapy and your testosterone has returned for some time (probably returned for at least a year).
Typically, radiotherapy will reduce your semen by something between half gone and completely gone. Also, if you have any, it may not look the same, because it's made from several parts mixed together as you ejaculate, and it is likely some parts may be missing more than others. You won't return to normal.