DALLAS (AP) -- The owner of a North Texas nuclear power plant has tabled its request for federal permission to expand.

Dallas-based Luminant Generation had asked the U.S. Nuclear Regulatory Commission for a license to double the number of nuclear reactors at its Comanche Peak plant from two to four.

However, in a letter to the NRC on Friday, Luminant said its Japanese-based reactor partner had decided to focus on restoring nuclear power in Japan after a 2011 earthquake and tsunami led to a disaster at the Fukushima nuclear power plant.

Mitsubishi Heavy Industries "has informed us that they will materially slow the development of their design control document for their new reactor design (for Comanche Peak) by several years. In addition, both (Mitsubishi) and Luminant understand the current economic reality of low Texas power prices driven in large part by the boom in natural gas," Luminant said in a corporate statement.

That boom was ignited by the use of hydraulic fracturing to release abundant natural gas resources in North Texas. Natural gas is used to fire the boilers of numerous electric power generating plants.

"Currently, it's just not competitive with gas," Ross Baldick, University of Texas engineering professor, told The Dallas Morning News. "Nuclear's capital costs are so high you can't win on it."

Also in the background is corporate parent Energy Future Holdings' flirtation with bankruptcy.

Luminant is keeping its application on file with the NRC, though.

"Luminant will continue to support nuclear power as part of the solution to Texas electric reliability and reevaluate this decision as conditions change," according to the company statement.

The plant is situated about 40 miles southwest of Fort Worth near the town of Glen Rose. Its two nuclear reactors have the capacity to generate 2,300 megawatts of electric power -- enough to power about 1.15 million homes in normal conditions and 460,000 homes in periods of peak demand, according to the company. The plans to add two more reactors would have lifted the plant's generating capacity to 5,700 megawatts.

The project drew opposition from environmental groups, which were heartened by Luminant's decision to place the expansion on hold.

Tom "Smitty" Smith, Texas director for Ralph Nader's watchdog group Public Citizen, told the Fort Worth Star-Telegram he had suspected that Energy Future Holdings has been keeping the Comanche Peak expansion application alive because "they would be valuable assets in bankruptcy."

"This stunning decision shows how little bankers on Wall Street value nuclear power," he said.

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