Disable Radiant Quests in Skyrim

There is no current way to do this. As well, many of the actual quests use aspects from the Radiant quest system. For instance, the quest Laid to Rest determines the race of the boss based on the Radiant system. This can also determine race and gender of many other NPCs.

There are two places where radiant quests will end up in your journal. They will either end up in the Miscellaneous tab, or in one of the Faction specific quest sections of your journal. Therefore, you know that you are done with the game's completion as soon as you have finished the capstone quest for each faction, and have no other quests outside the Miscellaneous section.

Plain and simple, I don't believe it's possible. So, no.

Also, as some of the comments pointed out, even if you could, there would be strong drawbacks and consequences for doing so.