Steam Generator Replacement
TMI Unit 1's steam generator replacement is part of AmerGen's overall commitment to investing in the future of Three Mile Island for 20 more years of safe, clean and reliable operations. It is an essential system to ensuring a continued electricity supply to the region.
In the steam generator, heated water from the reactor vessel flows through pipes into the steam generator. The heat from this water is transferred to a secondary water supply in the steam generator. These two supplies of water never mix. The heat causes the water to boil and creates steam. The steam spins the turbine, which drives the electric generator to produce electricity.
AmerGen has entered into a contract with AREVA to design and build two steam generators. TMI Unit 1's existing steam generators are inspected every two years during refueling outages and are monitored during operation. It is common across the industry to replace existing steam generators as part of the ongoing investment and maintenance of nuclear power facilities.
The cost of replacing TMI Unit 1's two steam generators is approximately $280 million. The replacement steam generators will have numerous material and design enhancements compared to the existing 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 by June 2009, and 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.
The plant's original control rod drive control system will also be replaced at the same time, with a new digital control rod drive system. The new control system will simplify and reduce the number of actions required by the control room operators. The control rod drive system is used to withdraw and control the position of the rods in the reactor during the fission process.