WASHINGTON, Oct. 17 (UPI) -- North Korea's mention of "more powerful" weapons in its statement admitting to a nuclear weapons program could mean the country thinks it can create a thermonuclear, or hydrogen, bomb, scientists told United Press International Thursday.
The North Korean government confirmed the existence of its uranium-enrichment and weapons development program to U.S. officials Oct. 2 after being confronted with evidence about it from U.S. intelligence sources. North Korea, officials said, also ominously warned it had even "more powerful" weapons.
The Bush administration disclosed the news late Wednesday in a series of apparently orchestrated leaks to selected U.S. media.
The ambiguous "more powerful" comment has been interpreted as a threat of biological or chemical weapons, but other meanings are possible, said Michael Levi, director of the Federation of American Scientists' Strategic Security Project.
"My gut reaction was that it must refer to thermonuclear devices, but that could be bluster," Levi told UPI. "Most of our debates (at the FAS) have turned on what exactly the translation was ... would you use the word 'powerful' to refer to a biological weapon (in that context)?"
In addition to the weapons-grade uranium program, U.S. and South Korean intelligence agencies suspect North Korea already has plutonium from its now-inactive Russian reactors.
Both elements are needed for a hydrogen fusion bomb, said Edwin Lyman, president of the Nuclear Control Institute, a Washington-based non-proliferation research and advocacy organization. There also are advanced, more powerful fission devices that use uranium and plutonium, he told UPI.
Unclassified scientific research on thermonuclear devices reveals a complex, two-stage bomb. A uranium chain reaction starts the process, compressing a quantity of deuterium, a heavy isotope of hydrogen, around a "spark plug" of plutonium.
The follow-on plutonium detonation heats the compressed hydrogen to the point of a fusion reaction, the same process that powers the sun.
Thermonuclear weapon yields can reach into the tens of megatons -- equivalent to millions of tons of the explosive, TNT, and hundreds of times more powerful than the Hiroshima bomb.
A 1 megaton device detonated on the Washington Mall would destroy every building within approximately three miles. Ordinary buildings up to six miles away would be flattened.
The equations and engineering involved in creating an H-bomb have taxed the most brilliant scientists in the United States, the former Soviet Union, Great Britain and France, Lyman said. Hard facts about the successful designs are very difficult to obtain, he said, so the North Korean comments sound to him like saber-rattling.
"At a minimum, you have to ensure you have a fission weapon that has a reliable yield ... there's a fairly small window of error for igniting the thermonuclear blast," Lyman said. "My perception is that it would be a very big reach to conclude they have a workable design at this point."
If the Bush administration had reason to suspect North Korea has such an advanced program, its response would have been much more forceful, Lyman said.
Testing is key to thermonuclear designs, Levi said, because the technology involved is not a straightforward development from fission weapons. India said it detonated a "boosted" weapon during its testing standoff with Pakistan in 1998, he said, but available seismic data suggested a simple fission bomb instead.
The challenges to creating a North Korean H-bomb should not be minimized, however, Levi said. The end result might not need to be turned into a missile warhead. A truck-mounted device -- therefore somewhat less complex -- could be driven to the edge of the Korean demilitarized zone and still get the job done, he said.
As troubling as the H-bomb idea is, a more troubling question is how North Korea could have managed to create and operate uranium-enrichment facilities clandestinely under the international scrutiny that followed the closure of the Russian reactors, Lyman said. Such an achievement casts serious doubts on efforts to limit worldwide proliferation of nuclear weapons, he added.
