Three Mile Island breaks operation record

26 October 2009

Unit 1 at the Three Mile Island nuclear power plant has been shut down for refuelling after operating for 705 straight days - a world record for a pressurised water reactor. The 870MW plant near Harrisburg, Pennsylvania is owned and operated by Exelon.

Before being shut down on 26 October, TMI-1 had run continuously since starting up from its last refuelling outage on 21 November 2007 (705 days). That beats the existing record of 692 days set earlier this year by the Calvert Cliffs Nuclear Power Plant in Maryland. The world record among all types of light water reactors is held by LaSalle Generating Station Unit 1 in Illinois, which operated for 739 continuous days.

Three Mile Island’s achievement is a reflection of the company’s dedication to the safe and reliable operation of our plants,” says Joe Grimes, senior vice president, mid-Atlantic operations for Exelon Nuclear. “Our focus is on human performance and equipment reliability. One outcome is record operating runs such as this one.” Earlier this month Exelon said that it has invested more than $500 million on plant equipment to ensure continued safe operations.

During this year's outage workers will complete over 25,000 separate operational, maintenance and testing activities, including replacement of the unit’s two steam generators. The steam generators, which weigh more than 510 tons each, were delivered to the site in early October after an eight-week trip from Areva’s Chalon/St-Marcel manufacturing facility in France. The steam generator replacement project is expected to cost around $350 million.

Last week the US Nuclear Regulatory Commission renewed the TMI-1 operating licence for an additional 20 years, until 2034. Following thorough reviews of Exelon's 2550-page licence renewal application NRC staff concluded there were no environmental impacts or safety concerns that would preclude renewal of the licence.

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