NNSA needs massively more powerful computers to model modern nuclear weapons effects, report says

Understanding the cradle-to-grave requirements of modern nuclear weapons will require significantly more powerful computing capacity than the U.S. nuclear enterprise plans to develop, the National Academy of Sciences reported Thursday.

The National Nuclear Security Administration (NNSA) “needs to fundamentally rethink the strategy for its next generation of high-performance computing” in order to achieve “post exascale” computing capacity that can perform more than a quintillion operations – a number equal to one followed by 18 zeros – per second, according to the report. There are one billion billions in one quintillion.

That sort of massive computing power is needed to perform modeling and simulation on modern nuclear weapons, which are no longer detonated to study their effects since the U.S. voluntarily ceased underground nuclear explosive testing in 1992.

“These simulations require leading-edge computer platforms, sophisticated physics and engineering application codes, and expertise in applied mathematics and computer science for the design, engineering qualification, surveillance, maintenance, and certification of the nuclear stockpile,” according to the academies’ report, mandated by the 2021 National Defense Authorization Act. 

A committee, with participation from multiple NNSA sites and academic partners, was asked to evaluate future technology trajectories as well as the U.S. industrial base required to meet those needs.

“Much progress has been made in understanding the basic physical processes that govern a nuclear weapon, there remain phenomena central to the operation of modern nuclear weapons for which understanding remains incomplete,” the report reads. “The computational resources required for full numerical resolution of these physical processes typically exceed exascale capability.”

The Department of Energy has led the charge to develop exascale computing, installing its first system in its Office of Science in 2022 through the Exascale Computing Project 2. NNSA will take advantage of what its parent department has already accomplished, but its demand will outpace exascale computing within the next two decades, the report said. 

“Instead, NNSA will need to reevaluate how its mission problems, not limited to physics simulations, are best solved through advanced computing, and rethink what type of models, algorithms, and data analysis techniques are suited to each problem; what computing capabilities will be needed; and how it can best acquire those capabilities,” the report said. 

The committee made several recommendations in the 85-page report, including development of an “aggressive computing roadmap” to achieve the computational volume required and reduce the time needed for complex calculations from years or months to days or hours.