Still facing a series of regulatory hurdles to their planned merger, Duke Energy and Progress Energy have cleared what might be described as a speed bump along the way, winning approval from the Nuclear Regulatory Commission that's necessary to consummate their $26 billion deal.

The NRC said Raleigh-based Progress will be able to transfer its nuclear operating licenses to Charlotte-based Duke when the two companies are combined.

Progress currently operates five nuclear reactors at four sites in the Carolinas and Florida, including the Shearon Harris plant in southwestern Wake County. When those units are combined with Duke's seven units, Duke will operate the largest regulated nuclear fleet in the country.

The NRC ruling, issued Friday, is a formality with little practical consequence. Progress is the sole operator of its nuclear plants, and will remain the operator when it becomes a subsidiary of Duke. The license transfer will not affect plant operations, decommissioning funding or financial qualifications.

Nuclear critics in this state and elsewhere have once again asked federal nuclear regulators to halt the approval process for a next-generation reactor design favored by Duke Energy, Progress Energy and other Southern electric utilities.

If the petition were to succeed, it would severely set back this nation's nuclear revival by disqualifying the Westinghouse AP1000 reactor design that has shown greatest promise to the industry.

Duke and Progress have selected the AP1000 for new reactor construction in North Carolina, South Carolina and Florida.

The critics, including N.C. Waste Awareness and Reduction Network, based in Durham, asked the Nuclear Regulatory Commission to terminate rulemaking on the AP1000, saying the design is fundamentally flawed and unsafe. They say the review process should not begin until the reactor design is completed.

Federal nuclear safety regulators are stepping up oversight at Progress Energy's Robinson nuclear plant in South Carolina in the wake of two fires and other problems that forced the plant to shut down last year.

The Nuclear Regulatory Commission said today the Robinson plant had an excessive number of unplanned shutdowns last year due to performance problems.

The plant failed to implement required procedures and did not develop operator training, the NRC said.

The agency said the plant continues to operate safely.

Federal regulators on Thursday gave the go-ahead for Progress Energy's Shearon Harris nuclear plant to try an alternate way to meet fire safety standards that have eluded the facility in Wake County for more than a decade.

Shearon Harris will be the nation's first nuclear plant to attempt to meet fire safety standards through the Nuclear Regulatory Commission's experimental approach. The new rules don't apply a uniform standard throughout the nuclear plant but instead set thresholds based on varying risk factors.

The NRC is testing out the new safety standards on two nuclear plants. The other plant applying to use them is Duke Energy's Oconee plant in South Carolina.