'Subcritical' tests not same as nuclear tests

The Nevada Test Site is host to programs intended to ensure the U.S. nuclear arsenal remains safe and reliable, according to the director of public affairs for the National Nuclear Security Administration, Nevada State Office.

But that doesn't mean the NTS is about to resume underground nuclear detonations.

Darwin J. Morgan, the director, was responding to concerns that an increase in scientific activity at the site might be a prelude to the resumption of underground nuclear explosions. He was interviewed Tuesday via cell phone while driving back to Las Vegas following the latest "subcritical" test at the NTS.

The National Nuclear Security Administration is the branch of the U.S. Department of Energy that administers the Nevada Test Site. The NTS, where nuclear explosions were carried out in the past, is a reservation of 1,350 square miles northwest of Las Vegas, reaching to within about 65 miles of that city.

By "subcritical," planners mean that nuclear detonations do not take place even though radioactive materials are used in the experiment. The latest test, "Armando," was to examine the behavior of plutonium when shocked by conventional high explosives.

"It went very well," Morgan noted.

Besides this "subcritical" series, the NTS has a two-stage gas gun that experiments on plutonium — the Joint Actinide Shock Physics Experimental Research (JASPER). Also, a pulse-power machine was moved to the site from the Los Alamos National Laboratories in New Mexico to conduct experiments on non-nuclear material, he said.

These projects are part of the Nevada Test Site's work on its Stockpile Stewardship Program, to ensure America's nuclear weapons are safe and reliable, he said. The results of such experiments can be used to certify to the president that the weapons are in good condition.

As long as these non-nuclear explosion tests provide results allowing officials to make that finding, "there's no need to conduct a nuclear weapons test," he said.

One of the biggest misconceptions about the Nevada Test Site, he said, is that subcritical tests are the same as nuclear test. A nuclear test is defined by treaty.

"It's where you obtain yield," he said.

That is, an experiment should not be considered a nuclear test just because it uses radioactive material like plutonium. To be "nuclear," by that definition, a test must unleash the power of the atom's nucleus — as when a nuclear bomb detonates.