N. Korea’s second nuke looks little improved

TOKYO – North Korea’s detonation of a nuclear device Monday appears not to have been a significant technical advance over its first underground test three years ago. But it has triggered a swifter, stronger and more uniform wave of international condemnation, most notably from the isolated nation’s historical allies, China and Russia.

The U.N. Security Council moved quickly in an emergency meeting Monday to condemn the test, saying it constituted a clear violation of a 2006 U.N. resolution barring the communist state from exploding a nuclear weapon.

Earlier, the Chinese government, which is North Korea’s main economic patron, said it was “resolutely opposed” to the nuclear test and told Pyongyang to avoid actions that heighten tensions and return to multi-nation talks focused on dismantling its nuclear program. China’s response Monday was significantly more pointed than it was to North Korea’s first nuclear test, in October 2006.

President Barack Obama, whose staff was informed of Monday’s test about an hour before it took place and who had been briefed several times in the past week about the possibility, accused North Korea of “blatant violation of international law.”

“By acting in blatant defiance of the United Nations Security Council, North Korea is directly and recklessly challenging the international community,” Obama said outside the White House. “North Korea’s behavior increases tensions and undermines stability in Northeast Asia. Such provocations will only serve to deepen North Korea’s isolation.”

The test, described as “successful” by North Korea’s official Korean Central News Agency, escalates a pattern of provocation that this spring has included the long-range missile launch, detention of two U.S. journalists, kicking out U.N. nuclear inspectors, restarting a plutonium factory and halting six-nation negotiations on its nuclear program.

North Korea said its second nuclear test was more powerful and better controlled than its 2006 test, which many experts characterized as a semi-failure.

But several U.S. experts on nuclear weapons said Monday’s test demonstrated that the North Koreans have not yet mastered the technology of creating a reliable nuclear bomb.

“The simplest hypothesis is that they’re trying to build a weaponizable device and they’re still not that good at it,” said Jeffrey Lewis, director of the Nuclear Strategy and Nonproliferation Initiative at the New America Foundation, a nonprofit group.

The explosive yield from Monday’s test was in the range of 2 to 4 kilotons, which is two to five times that of the 2006 test, according to Siegfried Hecker, a periodic visitor to North Korea’s nuclear complex in Yongbyon who is a former director of the Los Alamos National Laboratory and current co-director of Stanford University’s Center for International Security and Cooperation.

“You would expect 10 to 20 times that yield,” said Theodore Postol, a professor of science, technology and national security policy at the Massachusetts Institute of Technology. “These guys have not solved the problem.”

On a technical level, Postol said, the North Koreans appear to be having trouble building a device that uses explosives to compress plutonium into a perfect ball, which creates a uniformly spherical implosion and the maximum possible explosive yield.

“It means they are not yet able to confidently build an experimental weapon and they may not be able to determine what they did wrong,” Postol said.

North Korea has for years been the target of international sanctions intended to limit the country’s access to bomb- and missile-making technology. But a senior administration official said that although the sanctions have undermined the North’s economy, they have had little direct effect on its “entirely indigenous” nuclear program.

The government mines its own uranium, builds laboratories using its own technical expertise and generates its own plutonium, making it hard to stop the process from the outside, the official said.

After it exploded a small nuclear device in 2006, North Korea agreed to begin shutting down its main nuclear reactor and began to disable it. It did so in return for food, fuel and diplomatic concessions, including a move by the Bush administration last year to remove North Korea from a U.S. list of state sponsors of terrorism. But the negotiations did nothing to stop North Korea from trying to improve the quality of its nuclear devices.

“It is not surprising that the North tested again,” said Hecker, who has occasionally been in contact with North Korean nuclear scientists. “The October 2006 test must have raised as many questions for them as it answered. The technical people must have been eager to conduct another test or two.”

Japanese Prime Minister Taro Aso said Monday night that his country “absolutely cannot tolerate” the nuclear test because North Korea is also beefing up its ballistic missile capability, which “could be a means of transportation for weapons of mass destruction.”

Japan dispatched three military aircraft Monday night from three bases to monitor the possible presence of radioactive substances in the air, the Defense Ministry said. Japan’s anxiety about the test is heightened by its vulnerability to attack from nearby North Korea, which has more than 200 mid-range Nodong missiles capable of striking most of the country.

Significantly at the United Nations on Monday, it was Russia’s envoy, Vitaly Churkin, who spoke on behalf of the Security Council’s 15 members. Until the early 1990s, the former Soviet Union was by far the most important supporter of North Korea’s government.

“The members of the Security Council voice their strong opposition to and condemnation of the nuclear test conducted by” North Korea, said Churkin, who is serving as the council’s president this month.