The United States is the largest producer of nuclear power in the world, but all that power leaves some potent leftovers behind.

Right now there are about 80 sites around the country where an estimated 80,000 metric tons of spent nuclear fuel are stored.

That's potentially deadly radioactive material that will stay poisonous for thousands of years.

For nearly four decades, politicians have battled over where to store it all.

CBS News’ Jonathan Vigliotti went on a rare tour of Yucca Mountain. 

About 100 miles outside Las Vegas, deep in a remote patch of desert, there's a $19 billion hole in the ground.

That's how much it has cost to fight over and build this five mile test tunnel under Yucca Mountain. Now largely abandoned for almost a decade, it was designed to be the answer to America's nuclear waste problem - a problem still piling up at far away places like San Onofre Nuclear Power Plant, midway between Los Angeles and San Diego, where engineers produced power for half a century.

"This is spent fuel from the unit two reactor …"

Ron Pontes helps manage the decommissioning of San Onofre, which shut down in 2012.

"How many years of spent fuel are we looking at here?”

Pontes answers, "…about 50 years’ worth of operation here …"

Under this massive concrete slab, 536 tons of radioactive spent nuclear fuel from the plant is temporarily buried.

"The fact that Yucca Mountain had failed to materialize as the nation's repository for spent nuclear fuel has stranded fuel not only at this site but at sites across the nation."

Congress designated Yucca Mountain as the location for a national permanent nuclear waste repository back in 1987. A test tunnel was dug but never licensed.

"It is an isolated location which has the right geology which can make the difference for safe use of nuclear power and storage of nuclear waste for generations and generations to come."

Wyoming Senator John Barrasso is now pushing legislation that would re-start the licensing of Yucca Mountain, a process the Obama administration put on hold almost a decade ago after opposition from a bipartisan group of Nevada politicians.

"I have concerns about the science here …"

Senator Catherine Cortez Masto of Nevada has been fighting Yucca Mountain for over 20 years.

"Part of the infrastructure that is necessary is to build all of the rail lines that need to come across Nevada, across this country, to bring it there. And a lot of those rail lines and the shipments would come right through the heart of Las Vegas."

"This will be a bottleneck for all of this radioactive waste if, in fact, Yucca Mountain does go through?"
Cortez Masto answers, "It's a bottleneck. Two shipments a day for 50 years. What? I mean, it's crazy."

Cortez Masto invited CBS News along on a rare visit to the tunnel, hosted by William Boyle from the Department of Energy.

"How good of a site is this for the country's nuclear waste?" 

"Well, the department felt it was good enough that we submitted the license application in 2008 …" says Boyle. 

"Do you agree with that submission?" 

"It wouldn't have been submitted if I didn't agree"

"What are you thinking?" 

"I disagree …"

Cortez Masto says some scientists worry that water in the ground will mix with nuclear waste and enter the drinking supply of small nearby farming communities. Boyle feels that risk is safely manageable. 

"You say what's unfolding here is political science. What do you mean by that?"

Cortez Masto says, “Because when they passed the Nuclear Waste Policy Act… We didn't have any seniority at the time, in the state of Nevada, to be able to change that. And so literally, it got crammed down Nevada's throat. 

At what point does time just run out in the debate and it becomes just such an issue that -- all of this waste collecting and we just say we have to put this somewhere? 

"It's my impression that if we were to ask the people that live near San Onofre, live near San Diego, that they reached that point a while ago"

Temporarily storing nuclear waste at places like San Onofre is costing hundreds of millions of dollars. It's money subsidized by utility customers, taxpayers, and the very same federal government that can't agree on what to do with it.

"We collected money from our customers that went to the federal government and they haven't used that money to build anything. We would like to see the government do their job and come get the fuel like they promised,” says Pontes.

(CBS News)