The Three Mile Island Unit 1 is a pressurized water reactor with a net generating capacity of 852 MWe. Unit 1 first came online on April 19, 1974, and began commercial operations on September 2, 1974.
TMI-1 is licensed to operate for 40 years from its first run, and in 2009, was extended 20 years, which means it may operate until April 19, 2034.
TMI-1 has a closed-cycle cooling system for its main condenser using two natural draft cooling towers. Makeup water is drawn from the river to replace the water lost via evaporation in the towers. Once-through cooling with river water is used for the service water system which cools auxiliary components and removes decay heat when the reactor is shutdown.
When TMI-2 suffered its accident in 1979, TMI-1 was offline for refueling. It was brought back online in October 1985, after public opposition, several federal court injunctions, and some technical and regulatory complications.
Eight filters used for cleaning the secondary loop water. These filters are designed to stop minerals and impurities in the water from accumulating in the steam generators and increasing corrosion rates in the secondary side.
Updated on 15 Apr 2016.