ORNL Federal Credit Union has been open since 1948. It's the 4th largest credit union in Tennessee with assets totaling $2.26 Billion and providing banking services to more than 170,000 members. Membership: The credit union is a community-based financial institution. People living, working, or worshipping in the credit union's geographic area can become a member and access banking services. Membership is also open to immediate family of current members.