U.S. nuclear output dropped as Exelon Corp. shut the Three Mile Island reactor in Pennsylvania and Dominion Resources Inc. idled the North Anna 1 plant in Virginia. Twenty-six of the nation's 104 reactors are offline.

Output from nuclear plants fell 3.7 percent from Oct. 23 to 73,706 megawatts, according to a report today from the U.S. Nuclear Regulatory Commission and data compiled by Bloomberg. The total represents 73 percent of capacity.

Exelon Corp. idled the 786-megawatt Three Mile Island reactor for refueling and maintenance, according to an e-mailed statement. The unit is on an island in the Susquehanna River near Middletown, about 10 miles southeast of Harrisburg.

Dominion Resources Inc. shut the 903-megawatt North Anna 1 reactor in Virginia after identifying a "pinhole leak" in the water purification system, said Rick Zuercher, a company spokesman. The plant is 45 miles northwest of Richmond, Virginia, where Dominion is based.

FPL Group Inc. shut the Turkey Point 4 reactor in Florida. Another unit, Turkey Point 3, is operating at 100 percent. Each has a capacity of 693 megawatts. The plant is 25 miles south of Miami. FPL is based in Juno Beach, Florida.

The Tennessee Valley Authority shut the 1,126-megawatt Sequoyah 2 reactor near Chattanooga, Tennessee, for refueling. Plant operators will perform maintenance on the low pressure turbine and several cooling system pumps while the unit is down, said Craig Beasley, a company spokesman. Sequoyah 1 is operating at full capacity.

The Tennessee Valley Authority idled the Browns Ferry 3 reactor in Alabama. The unit was operating at full capacity of 1,115 megawatts Oct. 23. The Browns Ferry station, which has three reactors, is near Athens, Alabama, close to the Tennessee border. Units 1 and 2 are operating at full capacity, according to the commission. The Tennessee Valley Authority is based in Knoxville, Tennessee.

Southern Co. boosted the 1,109-megawatt Vogtle 1 reactor in Georgia to 94 percent of capacity. The unit is coming back online after refueling. Another reactor at the plant, Vogtle 2, is operating at full capacity. The plant is near Waynesboro, Georgia, close to the South Carolina border.

Dominion Resources Inc. increased output from the Kewaunee reactor in Wisconsin to full capacity from 33 percent Oct. 23. The 556-megawatt Kewaunee reactor is 35 miles southeast of Green Bay.

Exelon Corp. started the Clinton reactor in Illinois and is operating the unit at 50 percent of capacity. The reactor was taken offline Oct. 15 after the loss of a recirculation system pump, said Bill Stoermer, a company spokesman. The 1,065- megawatt unit is 160 miles southwest of Chicago.