@robertov
It is possible that a small amount of semen could be produced still. More likely the following.

Reduced/No Volume: Radiation causes tissues in the prostate and seminal vesicles to scar or become fibrous. Since these glands produce \(90\text{--}95\%\) of the fluid in semen, this damage results in little to no liquid being produced.What comes out? If any fluid is produced, it is likely only a very small amount of clear "pre-cum" (fluid from Cowper's glands), which are less likely to be damaged by radiation than the main prostate/seminal vesicle glands.