From Pyongyang to Tehran, with nukes

North Korea's tests are not the scary part. It's the country's collaboration with Iran.

By Siegfried S. Hecker

International condemnation of North Korea's underground nuclear test Monday resonated the world over -- just in time for Pyongyang to defiantly test two short-range missiles. After the U.N. Security Council condemned Pyongyang's long-range rocket launch on April 5, the country walked away from all previous nuclear agreements and threatened to restore normal operation of the Yongbyon nuclear plant, reprocess spent fuel rods to extract plutonium bomb fuel, pursue a light-water reactor, conduct nuclear tests, and launch intercontinental ballistic missiles. Kim Jong Il and company seem intent on pushing the limits of international patience, and raising the stakes with each provocation. But how worried should the world be? That is, what is North Korea actually capable of doing?

Concern over North Korea's tests is warranted. Pyongyang is on a well-planned trajectory to enhance its nuclear and missile capabilities -- something that officials made very clear when I visited the country in February. North Korea had slowed down the disablement of its nuclear facility, Yongbyon. It then launched a multistage rocket and walked away from the nuclear talks. Pyongyang is strengthening its "deterrent" threat by building more bombs, and possibly more-sophisticated ones at that.

But it is what North Korea did not threaten that should give us greatest concern: expanded nuclear and missile cooperation with Iran. The two countries' abilities and needs are highly complementary, and past collaboration tells us that the diplomatic channels may be as well.

North Korea shut down Yongbyon in July 2007, but began to restart the facility last month. The country has now restored the reprocessing facility and has begun extracting roughly 8 kilograms of plutonium from spent fuel. Although Yongbyon will not be able to complete reprocessing for four to six months, the anticipated increase in plutonium is what has allowed it to conduct this week's nuclear test. Without the additional plutonium, Pyongyang was limited to 26 to 50 kilograms, or roughly four to eight bombs' worth. Its small nuclear arsenal was likely also primitive; its first nuclear test in 2006 was only partially successful. Hours before the test, Pyongyang informed China that it would conduct a test at 4 kilotons, but it achieved less than 1 (by comparison, the bomb at Nagasaki yielded an explosion of 21 kilotons). It appears the North Koreans scaled back their original design to 4 kilotons to avoid a massive breach of the test tunnel.

The test this week, however, was more successful, producing a yield that I estimate at 2 to 4 kilotons based on currently available seismic measurements and estimates of the test site geology. This test will enhance Pyongyang's confidence in its arsenal and may be an important step toward miniaturizing warheads to fit on its missiles. Still, the size of North Korea's nuclear arsenal will remain restricted by its limited plutonium inventory. Fully capable nuclear-tipped missiles will require further tests, so the sequence of this week's provocative steps foreshadows more of the same.

For now, North Korea will remain somewhat trapped by its minimal plutonium supply. To make more, Pyongyang would have to restart its Yongbyon reactor. It will take approximately six months to prepare fuel for the reactor and to rebuild the cooling tower that the country destroyed last June as a symbolic gesture. Once fueled, the reactor will produce 6 kilograms of plutonium, roughly one bomb's worth, per year for the next decade or so. Pyongyang is not currently capable of ramping up plutonium production from there. The threat to develop its own light-water reactor is not a great concern for plutonium production, but it does likely signal that North Korea will now seriously explore uranium enrichment capabilities. But it would take many years for Pyongyang to develop the uranium route to the bomb.

Of course, there is a terrifying way that North Korea could overcome its limitation while simultaneously helping another nuclear aspirant: It could work with Iran. Pyongyang lacks uranium centrifuge materials, technology, and know-how; Tehran has mastered them. Pyongyang has practical uranium metallurgy capabilities; Tehran has little. Pyongyang has its own nuclear test data; Tehran does not. Pyongyang knows all facets of plutonium technology; Tehran has little more than a plutonium-producing reactor under construction. Pyongyang helped Tehran establish a missile capability; now, Tehran's crash missile-test program and Pyongyang's long-range rocket tests could prove mutually beneficial.

Preventing escalation of nuclear and missile cooperation is critical to avoid destabilizing Northeast Asia and the Middle East. The urgency of this threat is underscored by North Korea's recent covert construction of a nuclear reactor in Syria and its extensive ongoing cooperation in missile technology with Iran. At least in its nuclear reach, Pyongyang isn't quite as isolated as it seems.

Siegfried S. Hecker is codirector of the Center for International Security and Cooperation at Stanford University and director emeritus of Los Alamos National Laboratory.

Photo: JUNG YEON-JE/AFP/Getty Images