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.

Asked if he foresees the resumption of underground nuclear testing, Morgan said, "At my level, I have no way of knowing that."

If at some time in the future Test Site personnel can't confirm that nuclear weapons remain safe and reliable, a nuclear test might be considered to check the status of the arsenal.

"That's when the debate would occur whether we need to do a test," he said. It would be a careful process, he added.

"Since we did the last underground (nuclear explosive) test in 1992, we've been under a mandate to maintain test capability," Morgan said.

Until recently, the NTS was under orders to be able to resume that type of testing within 24 to 36 months, he said.

"Then in October, Congress passed legislation that narrowed that window," Morgan said.

The new mandate is to be able to resume testing in 18 to 24 months after a notice to do so.

"There's no ramping up," he said. "We have to be ready on a quicker time frame to do a test if we're so directed by Congress or the president."

Asked about the discussion that the Test Site could begin experiments with "bunker buster" devices, he said nothing going on there is associated with such a project. The subject is strictly part of policy considerations now, not operations.

"One of the big programs that we've got going out here is we're training first-responders," he said.

This fiscal year, about 8,000 firemen, police officers, emergency medical technicians and others were trained how to respond to a terrorist incident involving radiation.

"We've got the facilities out here to be able to bring them in and give them hands-on experience, using controlled radiation sources so that they can learn how to measure it, what they're looking at, how to do the appropriate decontamination," he said.

Associated with that sort of approach, the Department of Homeland Security wants the NTS to begin doing research to improve radiation detection. The devices would be used at border crossings, ports of entries and on highways to check for smuggled radioactive material.

The radiological defense complex would replicate roads and other facilities, he said, "so we can test the sensors . . . and use radioactive sources."

E-mail: [email protected]