NUCLEAR WEAPONSScientific Discovery for Stockpile Stewardship

Published 30 September 2022

Following the U.S. last nuclear test in September 1992, the Department of Energy’s national labs convened to develop a strategy and map out an R&D effort that would come to be known as the Stockpile Stewardship Program (SSP). Its mission was ensuring the readiness of the nation’s nuclear deterrent force without nuclear tests.

The last nuclear test, code-named Divider, took place thirty years ago, on 23 September 1992. That year, President Bush declared a temporary moratorium on nuclear testing, which became permanent during the Clinton administration. This ending of the era of nuclear testing was also the beginning of stockpile stewardship.

Leaders from the Department of Energy (DOE), and Lawrence Livermore, Los Alamos, and Sandia national laboratories, convened to develop a strategy and map out an R&D effort that would come to be known as the Stockpile Stewardship Program (SSP). Its mission was ensuring the readiness of the nation’s nuclear deterrent force without nuclear tests. 

This second article of a series surveys some of the significant scientific discoveries that have helped ensure the reliability of the nation’s nuclear stockpile.

Since the end of World War II, developing new nuclear weapons was a matter of designing, testing and adjusting the design to achieve the desired explosive yield and other performance goals, and testing again. The U.S. conducted 1,054 nuclear tests, more than 1,000 of them at what was then known as the Nevada Test Site, and researchers collected a great deal of data. “There was a lot of data that we didn’t completely understand or have the time to analyze because we had to move on the next test,” says Richard Ward, a physicist and weapon designer who started working at the Lab in 1982.

In 1992, the era of nuclear testing came to an end. Some in the nuclear national security community were surprised, a few were not. Certain researchers had thought about how to continue to design and assure the reliability of nuclear devices if testing ever ended. But most expected the design–test cycle to continue indefinitely. “It never occurred to me at the time that testing might end. I assumed I’d be working on testing my whole career,” Ward notes. But after it did, he and others moved on to new projects as the stewardship program began to ramp up. Earlier in his career, Ward had helped build the Nova laser, a predecessor of today’s National Ignition Facility (NIF), the most energetic laser in the world. He moved on to leadership positions in the Weapons and Complex Integration (WCI) Directorate.