A nuclear reactor projects at Watts Bar in Spring City, Tenn. - 

It’s been three years since the Fukushima disaster prompted Japan to try weaning itself from nuclear power, though that’s a position it now seems poised to reverse. In the U.S., four new reactors are under construction after a long lull.

Don’t call it a nuclear renaissance: The economics of nuclear power are a tough sell, especially in a time of cheaper natural gas.

"The idea that public fearfulness or the resistance of environmental groups is what killed nuclear power in the U.S. has always been nonsense," says Peter Bradford, a former member of the Nuclear Regulatory Commission.

Bradford says nuclear plants are expensive to build and hard to finance. Plus, electricity demand is lower than expected.