Every day, your body will probably generate at least one cell that would be cancerous if it wasn’t for your immune system. If that probability goes up slightly as a result of mildly increased radiation that day, it likely won’t overload the immune system’s capacity to deal with it. If it is overexposed to radiation, eventually the greater probability of cancerous mutations exceeds the immune system’s capacity.
Every day, your body will probably generate at least one cell that would be cancerous if it wasn’t for your immune system. If that probability goes up slightly as a result of mildly increased radiation that day, it likely won’t overload the immune system’s capacity to deal with it. If it is overexposed to radiation, eventually the greater probability of cancerous mutations exceeds the immune system’s capacity.