This is part of the America's Future series airing on FOX News Channel, looking at the challenges facing the country in the 21st century.

NEW YORK — Fear of an attack on one or more of the country's 104 nuclear power plants has been around at least since the aftermath of Sept. 11, when alarming reports surfaced of power plant security guards sleeping on the job and failures of plant siren systems.

But, nuclear power plants might not all be equal targets. Some say the focus should be on plants near metropolitan areas, even to the point of advocating the closure of those plants.

One plant at the heart of such a controversy is Indian Point, located just 35 miles north of Manhattan near the city of Peekskill, N.Y.

The plant is said to have been an alternate target for the Sept. 11 hijackers, but what are the chances of an attack there and what should be done?

"If I were God, I would shut down Indian Point," said Peter Stockton, senior investigator for the Project on Government Oversight, which monitors government fraud and waste. "I don't think the terrorists will go after a plant outside of Minnesota, but I do think they will go after one near a major metropolitan area."

Stockton began investigating security at the nation's nuclear power plants after 9/11 and worries that an attack on Indian Point would destroy New York City.

"The bad guys can ... blow a hole in the bottom of it, and when that happens, the water drains and then all of a sudden you get a cesium fire which can be deadly downwind," Stockton said. "By NRC's (the Nuclear Regulatory Commission's) calculation it will probably take New York City and one-third or a quarter of Connecticut, making it uninhabitable."

Click here to see more on terrorist designs on America's nuclear power plants.

But studies conducted by the NRC show that, not only are the chances of an aerial attack producing a major release of radioactivity low, the concrete-and-steel containment that shields most portions of a nuclear plant would withstand being hit by an airplane.

"We have spent over $2 billion upgrading things like intrusion-detection systems and vehicle barriers," said Marvin Fertel, vice president of the Nuclear Generation Division at the Nuclear Energy Institute. "Nuclear power plants are the only part of the critical infrastructure that does force on force. We also have a better integrated response working with federal, local and state response."

Adding to that, reactors at Indian Point are below ground level in a building that stands almost 200 feet tall, with walls up to four feet thick, reinforced with eight rows of overlapped steel bars more than three inches thick.

Of course no one can guarantee a 9/11-size terrorist force won't target a U.S. nuclear power plant.

"If I was a terrorist I would tell everyone that I would want to hit a nuclear power plant or a chemical plant or chemical, agriculture products, etc., because I am a terrorist and I want to terrorize people," Fertel said.

The NRC assures the public that any terrorist who studies these facilities will see they are hardened targets.

Click here to see more reports on America's Future.