Steam Generator Replacement
Three Mile Island Unit 1's steam generator replacement project is part of Exelon Nuclear's overall commitment to investing in the future of Three Mile Island for 20 more years of safe, clean and reliable operations. The steam generators are an essential system to ensure the future reliability of TMI Unit 1.
It is common across the industry to replace steam generators. Three Mile Island Unit 1 has two steam generators and the original steam generators' tubes are approaching the end of service life. To ensure the future reliability of TMI Unit 1, Exelon Nuclear is replacing both steam generators.
What is a Steam Generator?
Steam generators are heat exchangers used in Pressurized Water Reactors (PWR) like Three Mile Island. Steam generators act like giant double boilers. Pressurized hot water from the reactor enters the steam generator, passing through thousands of small tubes, similar to hot water passing through a car radiator. The heat from inside of the tubes is transferred to a second supply of water outside the tubes, which flashes into steam. The steam is then sent through large pipes to spin the turbines and generator, to produce electricity. The two supplies of water inside and outside of the steam generator tubes never mix.
The Replacement Steam Generators
Exelon Nuclear entered into a contract with AREVA NP Inc., to design and build TMI's replacement steam generators. The cost of replacing TMI Unit 1's steam generators is a $300 million investment into the plant. The replacement steam generators will have numerous material and design enhancements compared to the original steam generators, such as Alloy 690 tubing for reliability and longevity, use of forgings to minimize pressure vessel welds, and improved access for inspections.
The new steam generators are scheduled to arrive at Three Mile Island in fall 2009. Click here to visit AREVA's web page about the shipment of the steam generators to Three Mile Island. The steam generators will be installed during TMI Unit 1's refueling outage in the fall of 2009.
For more information about the steam generator replacement project, click here to access the steam generator fact sheet. Also, you can read through the Three Mile Island community newsletter that was mailed to nearby residents in August 2009.