WASHINGTON (Reuters) - The U.S. Nuclear Regulatory Commission told French nuclear power company Areva SA AREVA.PA it will publish as early as next week the names of U.S. reactors that contain components from its Le Creusot forge that is suspected of falsifying documents despite the company's claim that the information is proprietary.

A U.S. Nuclear Regulatory Commission sign is pictured at the headquarters building in Rockville, Maryland, March 21, 2011. REUTERS/Larry Downing

The written notice, dated Dec. 30 and seen by Reuters on Thursday, underscores rising tension between the U.S. nuclear regulatory body and Areva after French authorities opened an investigation last month into decades of alleged forgery relating to the quality of parts produced at the forge and used in power plants around the world.

The NRC has investigated whether the suspected falsification of documents poses any risks for U.S. nuclear plants, but has said it has found that the plants are safe.

“At this time, there are no indications of any specific safety concerns for U.S. reactors,” NRC spokesman David McIntyre said on Thursday.

Still, anti-nuclear power advocates, including Greenpeace, have pushed NRC to reveal which U.S. reactors have the components, saying that there could be risks to the public.

Areva sent the names of at least nine U.S. reactors with parts from Le Creusot on Dec. 15, but asked the agency not to name them due to proprietary business concerns. The NRC’s letter says the agency is not convinced the information is of competitive value, and will release the names 10 calendar days after receipt of the missive unless Areva challenges it.

“The NRC does not currently have sufficient information to determine that competitive harm would result from releasing this information,” the agency said in the letter.

A U.S. government source said that Areva has indicated it will not challenge the NRC’s publication of the names, which could occur as early as Tuesday. A U.S. spokesman for Areva did not immediately respond to a request for comment.

Reuters has independently identified four of the U.S. reactors that are using components from Le Creusot, a fifth that may contain them, and a sixth that may have them on hand for future installation.

All of the owners of the reactors said the components meet their quality standards and their reactors are safe.

Florida power company NextEra Energy Inc NEE.N said it had one reactor with one component from the Le Creusot forge but did not name the part or the reactor. NextEra owns eight reactors - four in Florida, two in Wisconsin, one in New Hampshire and one in Iowa.

NextEra spokesman Peter Robbins said the component “has performed its function for over a decade and been subject to detailed inspections and monitoring, none of which has ever detected any design or performance issues.”

Minnesota power company Xcel Energy Inc XEL.N said some components of the two reactor vessels at its Prairie Island plant were made at Le Creusot in the early 1970s. "Our testing and inspections are rigorous and have not identified any issues," Colleen Mahoney, an Xcel spokeswoman said.

In December, Dominion Resources Inc D.N said that its Millstone station in Connecticut has had a pressurizer from Le Creusot in service since 2006. Spokesman Ken Holt said at the time that the part is fully operational and will remain so for the life of the plant.

In addition, FirstEnergy Corp FE.N said its Beaver Valley reactor in Pennsylvania has steam generators and reactor vessel heads manufactured by Spain's Equipos Nucleares SA, or ENSA, which may contain some components from Le Creusot. The parts were installed in Unit 1 but will not be installed in Unit 2 for a few years.

Another company, Entergy Corp ETR.N, which is listed on a Greenpeace report as having parts from Le Creusot, would not comment on whether its reactors have parts from the forge, saying it cannot comment on details related to its vendors.

There are 99 reactors operating in the United States producing about 20 percent of the nation’s power.

The Paris prosecutor’s office opened an investigation in December into Le Creusot alleging forgery, endangerment of lives, and aggravated deception and thousands of documents dating to 1965 were being looked at. Areva said then that it was fully cooperating with the investigation.