The number of American engineers and scientists with nuclear weapons testing experience is rapidly dwindling, according to Thomas D'Agostino, head of the National Nuclear Security Administration.
"I would say five years from now, [scientists with testing experience] would no longer be active employees of our laboratories," D'Agostino told reporters at a Defense Writers Group breakfast Thursday. "This is a clock that's ticking for all of us."
Since underground nuclear weapons testing stopped in the early '90s, the number of active employees who "had a key hand in the design of a warhead in the existing stockpile, and was responsible for that particular design when it was tested" has steadily decreased, D'Agostino said. He estimates that nationwide, the number of scientists with testing experience "may be down to the low teens."
The government has replaced underground warhead testing with computer simulations, which D'Agostino admitted "shouldn't be considered a one-to-one substitute" with field testing. Still, he said that under his watch, there won't be any future weapons field testing, and that he's "extremely confident we do not need to test the warheads."
Although many scientists with nuclear testing experience have retired or will retire in the next few years, D'Agostino said the agency can call them up to review younger scientists' computer simulations.
Besides being more environmentally friendly and safer, D'Agostino said computer simulations are able to more accurately diagnose problems with warheads.
"I look back at very challenging, unexplained technical problems during the testing days, tests where the yield was a tenth of what it was predicted to be, and there was absolutely no understanding of why that was the case," he said. After using computer simulations, the agency was able to determine exactly what was causing the payload discrepancy.
"If we had known during the testing days that we were going to be entered into the phase of the program that we're in now [without testing], it would have been great to have more failures," he said. "Those failures are almost more important to help us do verification and validation of the computer code."
Between 1945 and 1992, the United States performed more than 1,000 field tests, which D'Agostino called a "nice, rich pool of information to compare ourselves to."
The United States reportedly has a stockpile of about 5,000 nuclear warheads. President Obama has repeatedly envisioned a future "world without nuclear weapons," and the Strategic Arms Reduction Treaty signed with Russia in 2009 limits the number of deployed nuclear warheads to 1,550. Although new nuclear warheads aren't under development, D'Agostino says the American stockpile is under a "surveillance" system to renovate existing warheads as they degrade and corrode.
Although D'Agostino says he has full confidence in the stability of America's nuclear arsenal, he admits not everyone shares that view.
"There are always going to be scientists and engineers that say, 'I actually have to see the test,'" he said.