The fuel is stored underwater and the concern is if that water were to dry up, the heat would melt the metal tubes holding the fuel and release cancer causing bi-products into the air we breathe.
Shearon Harris has four cooling pools and three are currently in use.
The ABC11 I-Team consulted Paul Turinsky, a nuclear physics professor at NC State, to learn more about the cooling facility and the spent fuel rods inside them.
"They're a pool," Turinsky said. "They look like a very deep swimming pool. Those pools have 20-30 feet of water above those assemblies, and that water has to be cooled."
But keeping them cooled has caused great concern among critics. Last year the investigative journalism group, Project Sensored, ranked safety issues at Shearon Harris the fourth most under reported story of the year because of the potential for fires in the spent fuel pools.
The local nuclear watchdog group NC Warn is just as concerned about terrorism.
"There's just no way to know if someone were trying to drain the water out of those pools either from the ground or an attack by air," said Jim Warren, NC Warn.
Progress Energy spokesperson Julia Milstead said, "It would be highly unlikely that any water would drain out of them."
The pools are kept in a secure building.
"We keep it in what's called the fuel handling building, which is next to the containment dome where the reactor is housed," she said. "The fuel handling building is made as robust as the containment dome, so you're talking about two to three feet of thick concrete walls and rebar. The floor beneath the pools is 12 feet thick of concrete."
So how concerned should we be that the most spent fuel under one roof in the country may be in our backyard?
"I feel fairly confident that the systems that are in place, and then their procedures that are in place, if the systems aren't working correctly, can handle the situation," Turinsky said. "Again, you need such a major disruption of all your facilities to get into the trouble the Japanese are in."
Shearon Harris has the largest capacity because its facility was designed for four reactors, but only one was built.
The plant is consistently ranked by nuclear regulators as one of the nation's better performing nuclear facilities.