July 7 (Bloomberg) -- Nuclear output was steady today as the Hope Creek reactor in New Jersey slowed to 85 percent from full capacity yesterday and the Millstone reactor in Connecticut remained shut.

Output from U.S. nuclear plants decreased by 172 megawatts, or 0.2 percent, to 97,962 megawatts today from 98,134 early July 6, according to a report from the U.S. Nuclear Regulatory Commission. The total represents 98 percent of U.S. capacity. Two reactors are offline, according to the commission.

The Millstone 2 nuclear reactor was shut after a power surge on July 3 made the grid unstable, according to a Dominion Resources Inc. spokesman.

The power surge, which caused the unit to automatically shutdown, may have been caused by a lightning strike outside of the plant, Ken Holt, a Dominion spokesman, said July 5 in a telephone interview. The reactor was not damaged in the incident and workers are performing maintenance not associated with the power surge while the plant is offline, he said.

There is no estimate for when 882-megawatt Millstone 2 reactor will be back online, the company said.

American Electric Power Co.’s Cook 1 reactor in Michigan remained shut after a September fire. It may return to service as early as the end of October, according to Bill Schalk, a company spokesman.

The commission’s report reflects the overnight and early morning operating status of the nation’s 104 nuclear power plants.

To contact the reporter on this story: Jenny Gross in New York at Jgross15@bloomberg.net; Aaron Clark in New York at aclark27@bloomberg.net

Last Updated: July 7, 2009 08:34 EDT