The idea here is magic is cast by altered mitochondria in-taking a new form of radiation which acts as a sort of manipulation net for ionizing or non-ionizing radiation depending on need. Then releasing it in a controlled manner shaped by neural feedback. The method by which this is done is unclear, but the effects of the various kinds of radiation on the body still occur while manipulation is occurring.
My question is how would the human body adapt to better handle in-taking normally dangerous amounts of ionizing radiation, thus removing one of the major hindrances on spellcasting? Alternatively, as I am no scientist, could someone kindly explain and/or propose another means of channeling/manipulating the radiation to cause different effects?