Prospect of atmospheric nuclear test by North Korea raises specter of danger
WASHINGTON - If North Korea follows through on its threat to conduct an atmospheric nuclear test, it would be a far more dangerous step than anything Kim Jong Un, its leader, has attempted - and poses a host of hard decisions for the Trump administration because attempting to stop the test could be as dangerous as letting it go ahead.
All six of the North’s nuclear tests have been underground, containing the radioactive fallout. But an atmospheric test - perhaps with a warhead shot over the Pacific on a North Korean missile, or set off from a ship or barge - would put the populations below at the mercy of the North’s accuracy and at the winds that sweep up the radioactive cloud.
That is why the United States and the Soviet Union banned such tests in their first nuclear test-ban treaty, more than a half-century ago.
It is exactly that fear of an environmental or humanitarian calamity that Kim appears eager to foster as he looks for ways to strike back at the United States, Japan and others seeking to choke off his money and trade. But experts who have been through the uncertainties of nuclear testing say there are risks all around, for Kim as well as his foes.
“It is not clear North Korea has that capability yet,” said Siegfried S. Hecker, former director of Los Alamos National Laboratory and the nuclear weapons expert the North Koreans let in to see their uranium enrichment plants years ago, when they wanted to make clear to the Obama administration that their atomic weapons program was moving ahead, unimpeded by sanctions.
“Besides,” said Hecker, now a professor at Stanford University, “a live missile test - one loaded with an H-bomb - poses enormous risk.” He recalled that when the United States performed such tests in the early days of the Cold War, “one blew up on the launchpad and one had to be destroyed right after launch, creating significant radioactive contamination.”
The North Koreans have studied this history, too, according to current and former U.S. intelligence officials. But the appeal of an atmospheric test is obvious: It would create a sense of fear that an explosion deep inside a tunnel in North Korea does not. The underground tests are detected on a Richter scale; an atmospheric test, like the kind the United States conducted at Bikini Atoll starting in 1948, creates a terrifying mushroom cloud.
The largest of those, a 1954 test code-named Castle Bravo, turned out to be roughly three times larger than U.S. bomb designers anticipated. They had made a mathematical miscalculation about the power of one of the nuclear fuels contained in the weapon, and the explosion spread radioactive material across the globe. Ultimately, Castle Bravo helped fuel the call for a ban on atmospheric tests.
No one knows what kind of test the North Koreans have in mind; the country’s foreign minister, Ri Yong Ho, did not specify when he raised the possibility when talking to reporters at the United Nations on Thursday. “This could probably mean the strongest hydrogen bomb test over the Pacific Ocean,” he said. “Regarding which measures to take, I don’t really know since it is what Kim Jong Un does.”
But the presumption is that if Kim decided to go ahead, the North would attempt to conduct the test by firing it on a missile, presumably to an empty spot in the Pacific. The goal would be to demonstrate that it had solved all the technological issues involved in delivering a nuclear weapon to a U.S. city.
But that form of testing - putting a live weapon on a missile - is particularly risky. Other countries have blanched at the potential for disaster, Hecker noted, including the Chinese, who conducted one missile launch with a live nuclear weapon in the warhead. It worked as planned, he said, but “the Chinese considered the risks unacceptable” and never tried it again. In the hands of the North Koreans, some say, it would be even riskier.
“This would be a regional nightmare” for East Asia, said Heather Conley, a former senior State Department official, now at the Center for Strategic and International Studies in Washington.
It is possible the threat will never come to fruition. Detonating a weapon inside a missile warhead, or even from a ship or barge, would be far more difficult for the North than setting one off inside a mountain, where engineers have months to wire up the weapon, and no time pressure.
It would require what experts call a “weaponized device” that could survive shocks, stresses and, if launched from a missile, the heat of re-entry into the atmosphere, something North Korea has never demonstrated it can handle.
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