Disabling North Korea’s Uranium Enrichment Program

by David Albright and Paul Brannan

January 20, 2011

On November 12, 2010, North Korea revealed to Stanford University Professor Dr. Siegfried Hecker a 2,000 gas centrifuge uranium enrichment plant on the grounds of the fuel fabrication complex at the Yongbyon nuclear site. If North Korean oral statements to Hecker are accurate, North Korea appears to have had more success than Iran, and over a shorter time period. It appears to have replicated the P2 centrifuge, which is more advanced than the P1 machine that Iran copied and installed in large numbers at the Natanz Fuel Enrichment Plant. While North Korea told Hecker that the plant is for producing low-enriched uranium (LEU) for use as fuel in a reactor program, the enrichment plant can nonetheless be easily used to make weapon-grade uranium (WGU) for nuclear weapons. In fact, the method to produce weapon-grade uranium using designs developed by Khan Research Laboratories (KRL) involves step-wise production of weapon-grade uranium, where the step devoted to the production of LEU requires about 70 percent of the total number of centrifuges to make weapon-grade uranium. North Korea would need a plant comprising only 1,000 centrifuges to top-off the LEU to weapon-grade at a rate of 50 kilograms of weapon-grade per year. This is enough for two nuclear weapons per year.

The plant’s continued operation represents a violation of the agreements established by the Six Party Talks. The U.S. and other members of the Six Party Talks should insist that North Korea commit to shutting down and verifiably disabling the plant as a precondition to negotiations resuming.

Common Ancestry

Both Iran and North Korea obtained centrifuge designs and centrifuges from Pakistan’s Khan Research Laboratory, run by A.Q. Khan. 1 However, North Korea received far more tutoring from KRL experts in manufacturing centrifuges than Iran. North Korea also appears to have decided to by-pass the far less capable P1 centrifuge and focus instead on the P2 centrifuge.

As is the case with Iran’s Natanz Fuel Enrichment Plant, the 3-4 percent LEU that North Korea will produce at the Yongbyon plant is nearly 70 percent of the effort towards making weapon enriched uranium for nuclear weapons. If any future negotiations stall, North Korea can further enrich its stock of LEU to weapon-grade relatively quickly either at the Yongbyon facility or at a smaller one it does not declare.

Libya received from the Khan network a Pakistani centrifuge plant design for making WGU, and North Korea likely received similar information. According to Khan’s statements, he provided North Korea with a design to make LEU. Given Khan’s frequent subterfuge, it is likely he also provided the designs to make weapon-grade uranium.

The design given to Libya comprises nearly 6,000 centrifuges divided into four steps, which make approximately 100 kilograms (kg) of WGU per year . 2 The first step enriches natural uranium up to 3.5 percent; the second step enriches from 3.5 percent to 20 percent; the third takes the material from 20 percent to 60 percent; and the final step enriches the 60 percent material to 90 percent, or weapon-grade. The first step consists of almost 4,000 centrifuges, or nearly 70% of the total number of centrifuges used.

Applying this design to the Yongbyon plant, North Korea could use the 2,000 P2 centrifuges at the Yongbyon plant as part of a 3,000 centrifuge system to make approximately 50 kg of WGU per year. In this event, it would need a plant with only 1,000 P2 centrifuges elsewhere in the country to enrich the 3.5 percent material produced at Yongbyon up to WGU. In this system, as mentioned above, the bulk of the enrichment effort would occur at the 2,000 centrifuge Yongbyon plant.

More Capable than Natanz

With North Korea’s claims about the output of the centrifuge, the Yongbyon plant would have approximately twice the capacity of the Natanz Fuel Enrichment Plant. During the last year, the effective annualized output of the Natanz plant has been about 3,500 separative work units (swu), a measure of centrifuge output. The North Koreans claimed to Hecker that each machine at the Yongbyon plant has a capacity of 4 swu per year. With 2,000 machines, the entire Yongbyon centrifuge plant would produce 8,000 swu per year, double that of Natanz.

The Natanz plant has recently produced on average about 133 kilograms of 3.5 percent LEU hexafluoride per month. If the North Korean plant were to produce 270 kilograms of 3.5 percent LEU hexafluoride per month, it would produce approximately 1,080 kilograms of low enriched uranium hexafluoride every four months. 3 This amount is enough for one nuclear weapon if further enriched to weapon-grade. North Korea could build up enough LEU in one year that after further enrichment would be sufficient for three nuclear weapons.

Even if the centrifuge plant became safeguarded in the near term, but continued to operate, North Korea could kick out monitors or inspectors and take the LEU to a secret enrichment site and upgrade it to weapon-grade. North Korea could rapidly make up any time lost in deferring the production of weapon-grade uranium.

Time to Focus on Enrichment

For years, the Six Parties have rightfully focused on the threat posed by North Korea’s plutonium program, despite the growing indications of a developing and undeclared gas centrifuge uranium enrichment program. The successful disablement steps taken in 2007 and 2008 at North Korea’s plutonium-production reactor and plutonium separation plant would likely never have occurred if suspicions about its uranium enrichment program were brought into the negotiations. That time, however, has passed. The new nuclear threat from North Korea is its gas centrifuge uranium enrichment program. The Six Party process should not accept the continued operation of the only site that North Korea has acknowledged to be a part of that program. The plant should be verifiably disabled.

1 Taking Stock: North Korea’s Uranium Enrichment Program, David Albright and Paul Brannan, Institute for Science and International Security, October 8, 2010, p. 21. See also 2 See Peddling Peril, by David Albright: 3 Assuming the same tails assay as used at the Natanz plant.

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