How does the human body deal with free radicals it creates itself?
Some enzyme-catalyzed reactions produce free radicals as short-lived intermediates, but these are likely to be contained within the enzyme active site until they can react further to form product. Example: ribonucleotide reductase - which catalyzes the formation of deoxyribonucleotides and enables the production of DNA. 

I can't think of any case where a biochemical process "intentionally" forms a free radical and then allows it to escape and cause damage elsewhere in the body. But biology is wonderfully varied and I would not want to say "never".