In the race to build the fastest computer in the world, America is back on top.

On Monday, a super-computer designed by IBM for the National Nuclear Security Administration (NNSA), took the first spot on the Top 500 list, a list that comes out twice a year ranking the 500 fastest computers on the planet.

It is the first time the U.S. has topped the list since November 2009.

The winning super-computer is called Sequoia, and it is housed at the Lawrence Livermore National Laboratory in Livermore, Calif.

Sequoia will be used to build complex models that let scientists test the nation's stockpile of nuclear weapons without having to do nuclear testing in the real world.

So how fast is the fastest computer in the world? Well, accordingto the Lawrence Livermore National Laboratory, it would take 6.7 billion people working with hand-held calculators 320 years to do the same calculation that Sequoia could power through in justone hour.

And the BBC reports that today's fastest computer is 273,930 times faster than the fastest computer of 1993.

"A calculation that took three full days to compute on the Thinking Machines in 1993 today can be done in less than one second on the Sequoia," Jack Dongarra, a computer scientist who helps oversee the Top 500 list, told the publication.

Sequoia takes up aboutone-tenth of an acre, a standard size for these computers, Dongarra said.

"They are enormous machines," he said in an interview with the Los Angeles Times.

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U.S. wins: Fastest supercomputer in world is right here