NORTH Korea calls it a "radio chemical laboratory" intended only for civilian use.
But the head of the watchdog International Atomic Energy Agency (IAEA) calls the new facility something else: a big plutonium-producing nuclear reprocessing plant.
In a country of North Korea's scientific level, the only use for substantial quantities of plutonium is a bomb - though IAEA chief Hans Blix did not say so flat out.
"What they term a laboratory is about 190 meters long, six stories high. It is therefore a very sizable construction," Mr. Blix said in an appearance before a congressional committee last week.
The inspectors of the IAEA are the world's international nuclear proliferation monitors. Among other things, they check up on the civilian nuclear programs of nations that have signed the safeguards of the Nuclear Non-Proliferation Treaty. The point is to make sure nuclear material isn't diverted into clandestine military programs.
North Korea finally acceded to these safeguards early this year, and IAEA teams have looked at the country's self-declared atomic sites. Many experts suspect North Korea of maintaining a hidden nuclear program, however, and feel there is much yet to find out about both inspected facilities and sites as yet undiscovered.
The "lab" is a case in point. North Korean officials admit they have used it for making small amounts of plutonium for experimental purposes, but they say its main use might be for waste disposal technology development, or with future nuclear "breeder" reactors.
Blix said he found none of these arguments very convincing.
Destruction of the plant, not yet half completed, "I don't think would hurt their peaceful nuclear program," the IAEA chief said.
US officials' main nuclear worry about North Korea is that somewhere in the country there are secret stockpiles of plutonium that could be used for weapon construction.
These suspicions are fed by such things as the fact that it would be very difficult to even attempt construction of the big "radio chemical lab" unless a smaller test facility had been built first, somewhere else.
Members of Congress pressed IAEA's Blix on whether he felt he had the power to make quick challenge inspections anywhere in North Korea to look for stockpiled material. Blix said that under Non-Proliferation Treaty safeguards he does have the right to ask to go anywhere he has good reason to suspect nuclear cheating is going on.
But "I do not think that concept allows us to vaguely say that we would like to go to anyplace in that country," he said.