"Where I was, It was easy," she tells CBS News correspondent Sharyl Attkisson.
Last week Quintana, 23, plead guilty to the national security breach at Los Alamos. In an exclusive interview with CBS News, she tells how she did it.
She was just 18, right out of high school, when the Lab hired her to archive documents. The job came with a security clearance that gave her access to highly sensitive weapons data.
Last summer Quintana claims she wanted to take some work home, a major security violation. She walked unchallenged into a special work vault with a computer storage device called a flashdrive.
"I had the flashdrive in my pocket when I entered the vault that day," recalls Quintana. "And at some point in the day I knew I wasn't being watched, the racks were open, simply inserted the flashdrive into my computer, took what I needed."
It was material related to underground nuclear weapons tests from the 70's, and she printed more classified documents — 228 pages.
"I printed out the pages I needed and put in my backpack with my school books and walked out like I did every day," said Quintana.
The materials were found accidentally months later by local police during a drug raid on Quintana's roommate in their trailer home, reports Attkisson.
It's an understatement to say that walking out with national secrets shouldn't have been so easy, especially in light of the rash of security scandals at Los Alamos: missing hard drives, even radioactive material smuggled out.
Tens of millions of tax dollars have been spent to upgrade security. Quintana's case raises the question. Have others, even spies, made off with top secret material?
Quintana says in the years she worked at the lab, nobody ever questioned or searched her. Not once.
"They were so lax about coming in and out," said Quintana.
Congress was so outraged that the Energy Department fired its top nuclear security official.
Quintana has agreed to cooperate with prosecutors and faces up to a year in jail. Her lawyer says Americans can thank her for one thing: exposing persistent gaps in security at a place guarding some of our most sensitive nuclear secrets.