Every thing that is in contact with the wort before boiling or during boiling needs to be clean but not sanitized. The boiling sterilizes the wort and everything in contact with it for a few minutes. An immersion chiller should be put into the pot in the last few minutes (10-15) of the boil to sterilize it. No need to sanitize it. Same goes for the brew pot, brew spoons used in the boil and any measuring utensils for items added to the boil.