The US ITER Project Office is located at 1055 Commerce Park Drive, Oak Ridge, Tennessee, 37830, which is a couple of miles outside the gates of the Oak Ridge National Laboratory. (To visit US ITER, do not go to the lab unless you have been specifically directed to do so by your on-site contact.) Parking is available at the Project Office building.
Detailed maps available:
US ITER – Oak Ridge Office (link to Google Maps)
Map from Knoxville Airport (TYS) to US ITER (PDF)
Information on visiting ORNL and the local area:
Details about visiting Oak Ridge National Laboratory and the surrounding area are available here.