The latest TOP500 ranking of the world’s fastest supercomputers is out this morning, and America is (finally) back on top. After nearly three years trailing supercomputers abroad–Japan’s K computer reigned supreme for most of last year, with China’s Tianhe-1A close behind–the U.S. Department of Energy’s Lawrence Livermore National Laboratory has stolen the top spot via Sequoia, a 16.32 petaflops (that’s a quadrillion floating point operations per second) IBM machine built from 96 racks containing 98,304 computing nodes and 1.6 million cores.

That pushes Japan’s K computer into second place while another DOE IBM machine, known as Mira, elbowed its way into the number three spot. In fact, IBM had a really good day, taking the number four spot as well with Germany’s SuperMUC. China rounded out the top five with Tianhe-1A.

What is the DOE doing with all those petaflops? Mostly, it’s making sure America’s nuclear weapons stockpile is both secure and ready to annihilate at a moment’s notice. But the ability to simulate and model nuclear weapons tests means we don’t have to actually conduct them (and haven’t had to for 20 years), and the science that falls out of those sims benefits the DOE in other tangential ways. The TOP500 list was released this morning at the International Supercomputing Conference in Hamburg, Germany. The complete list can be found here.