New York did something similar to save its ailing plants.But those actions have landed the states in court, where natural gas plant owners say the subsidies offer an unfair advantage and that the market should decide which power sources should be used.

The industry had warned that 10-15 power plants were at risk of closing.

"Two more plants announced premature retirement since that summit," Cohen said.

Experts worry about becoming too dependent on one fuel type, rather than relying on a mix of resources.

They say the reliability of the grid would be at risk without nuclear there to fill the gap.

But it has been disappointed in the federal government's lack of response. "This has fundamental national security implications," Cohen said.

"We cannot credibly claim global leadership while our domestic fleet shrinks." The U. has the largest fleet of nuclear power reactors in the world, with 99. Exelon, the largest nuclear utility in the country, which now owns the regional utility company Pepco that supplies power to the White House, sees fundamental problems in how the electric markets are managed that affect the economic health of nuclear plants.The news that the plant at Three Mile Island in Pennsylvania would be closing soon marked a significant turning point as a symbol of the industry's long history, perhaps even outweighing the plant's 1979 partial meltdown. The shale energy boom and fracking have caused the nation's supplies of natural gas to soar, making it a cheap, readily available fuel for new, efficient natural gas-fired power plants.Five plants have closed in less than four years, and six more are scheduled to shutter operations within the next five years, while many others are at risk of closing. The federal wholesale markets that regulate the supply of power favor the lowest cost electricity, and that pushes more expensive sources such as nuclear to the back of the line."In other words, the kind of actions taken in New York and Illinois are within federal rules, and other mechanisms are also permissible." Experts and officials have real concerns about the impact of plants closing in the coming decades.First, natural gas likely would become even more dominant, backed up by wind and solar.Both Commerce Secretary Wilbur Ross and Perry "have explicitly identified U. nuclear energy as imperative to our national security," Cohen said.