North Korea Learning to Make Crucial Nuclear Parts, Study Finds

SEOUL, South Korea — North Korean scientists have learned to produce crucial components of gas centrifuges inside their isolated country, undermining years of export controls and sanctions intended to stop the country’s enrichment of uranium for nuclear weapons, according to an analysis by two American arms control experts made available on Monday.

The analysis comes as experts have reported other signs that North Korea is activating or expanding its nuclear production facilities. Taken together, they suggest a new effort by the North to master all the facets of the nuclear production cycle — or perhaps to give the impression of nuclear progress that would drive new offers of talks or economic aid, in the view of some analysts.

The new study focuses on production of advanced centrifuges, a technically difficult feat that the United States and others have tried to make harder for the North with a network of sanctions and bans on the export of sophisticated parts and metals. If the North Koreans are successfully making their own parts, they would essentially invalidate much of the international strategy to force them to denuclearize and make it more difficult to monitor their production progress.

“That means, unfortunately, that we won’t be in a good position to spot them expanding the program through foreign shopping expeditions, and that policies based on export controls, sanctions and interdiction won’t get much traction, either,” said Joshua Pollack, one of theexperts presenting the findings this week. “The deeper implication, if they are able to expand the program unchecked, is that we’ll never be too confident that we know where all the centrifuges are. And that in turn could put a verifiable denuclearization deal out of reach.”

Mr. Pollack’s findings in collaboration with Scott Kemp, an expert on centrifuge technology at M.I.T., will be presented on Wednesday during a conference organized by the Asan Institute for Policy Studies in Seoul.

Mr. Pollack said he and Dr. Kemp had analyzed such open-source data as scientific journals, news reports and propaganda from North Korea to find evidence that the country is learning — or has already learned — how to make such crucial centrifuge components and related technologies and materials as uranium hexafluoride, vacuum pumps, frequency inverters, magnetic top bearings and maraging steel. He said that domestic production appeared to have begun no later than 2009.

North Korea shocked the United States in 2010 when its officials escorted a visiting American nuclear expert, Siegfried S. Hecker of Stanford University, to their main nuclear complex in Yongbyon, north of Pyongyang. There, they showed him a modern plant that they said housed 2,000 gas centrifuges, a technology that North Korea said it would use to enrich uranium for reactors but that American officials feared was a cover for making highly enriched uranium for atomic bomb fuel. Until then, the North’s sole source of weapons fuel had been plutonium gleaned from the waste of a mothballed nuclear reactor in Yongbyon.

Then, this April, at the height of tensions incited by the North’s nuclear test in February, the country declared that it would “adjust and alter the use of the existing nuclear facilities” for “bolstering up the nuclear armed force both in quality and quantity.” It said that included immediately restarting the Yongbyon facilities.

Last month, the Institute for Science and International Security in Washington cited satellite images to report that North Korea appears to have doubled the size of the building that housed the uranium enrichment plant in Yongbyon in recent months, and raising concerns that its enrichment capability would grow along with it.

This month, another monitoring group, the U.S.-Korea Institute at Johns Hopkins University, cited satellite photographs showing steam emerging from the Yongbyon reactor, suggesting that the North was following through on its vow to resume plutonium production.

South Korean officials declined to comment on the American scholars’ findings or on the North’s centrifuge capabilities in general.

Kang Jung-min, a nuclear scientist at the Korea Advanced Institute of Science and Technology who said he was familiar with the work by Dr. Kemp and Mr. Pollack, said he agreed with their analysis. Mr. Hecker, the Stanford professor, said he agreed for the most part with the analysis, though he said it was still unclear whether North Korea can indigenously produce the high-strength grades of maraging steel used in the rotor-tube of a centrifuge — one of the most difficult steps in centrifuge production.

“Having said that, if North Korea does indeed double the size of its Yongbyon centrifuge plant (all we know so far is that the roof is now expanded by a factor of two), then the likelihood of indigenous fabrication of maraging steel has increased,” Mr. Hecker said in an e-mail interview.

Since Mr. Hecker’s visit to Yongbyon in 2010, he and other experts have said that North Korea was likely to have produced and hidden many more centrifuges elsewhere in the country. Unlike the North’s old plutonium program, which involved a highly visible nuclear reactor, centrifuge plants are relatively easy to hide, they say.

In 2011, the mass-circulation daily Chosun Ilbo of South Korea quoted an anonymous defector from North Korea as saying that the country had been building centrifuges in Huichon, an industrial town about 35 miles northeast of Yongbyon, since the late 1990s. He said the North had imported the motors for centrifuges from such countries as Japan, France and Russia.

How to ensure that North Korea does not lie about the scale of its nuclear weapons program was a central dispute behind the collapse of six-nation talks aimed at ending the North’s nuclear weapons programs in late 2008. That dispute will be harder to settle if the North can produce centrifuges indigenously.

North Korea and its main ally, China, have recently tried to reconvene the six-nation talks. But the United States and its allies have said they will resume the talks only if the North agrees to eventually give up its nuclear arsenal.

As evidence to back up their analysis, Mr. Pollack and Mr. Kemp citedphotographs of Kim Jong-il, the North Korean leader who died in 2011, and his son and the current leader, Kim Jong-un, visiting underground tunnels to inspect increasingly sophisticated machine tools of the kind needed to make centrifuge rotors. They also cited accounts of iron- and steelmaking technologies in North Korean publications, as well as scientific reports and patent awards that they said described work on centrifuge production.

Mr. Pollack said that domestic production of centrifuge components might explain why American officials were caught off guard when the North unveiled its centrifuge plant in Yongbyon in 2010 and why North Koreans seem to have been able to expand the plant lately despite few indications of shipments of specialty steel and other imports from the outside in recent years.

“The most likely answer is, by producing the necessary components and materials at home,” he said.

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