EMPTY THREATS OR PROGRESS?
America’s nuclear history offers clues to North Korea’s thermonuclear mission
IT started with Albert Einstein. His famous E = mc2 revealed a vast asymmetry in the cosmic relationship between matter and energy. In time, experts looked into the possibility of exploiting the disparity.
Today, North Korea is hard at work on that agenda. Its nuclear program has succeeded in producing blast sin the Hiroshima range. In each case, trillions of atom sin a tiny smidgen of matter—estimatedat roughly 1 gram, the weight of a dollar bill—broke their nuclear bonds in violent bursts of primal energy.
The North now seeks to turn bits of nuclear fuel into even more powerful blasts. Experts say its ultimate goal is to transform an ordinary atomic bomb into a hydrogen bomb, which can raise its destructive force by 1,000 times.
“I can’ t imagine they’ re not workingon true thermonuclear weapons ,” said Siegfried S. Heck er, a Stanford University professor who from 1986 to 1997 directed the Los Al amos weapons laboratory in New Mexico, the birthplace of the atomic bomb, and whom the North Korean sin seeking recognition as a nuclear power have repeatedly let into their atomic facilities.
“But that’ s a big step ,” Heck er cautioned.“You have to pay attention to what they’ re doing but take their claims withagrainofsalt.”
On Sunday, the North fired a medium range missile in an actof defiance, its second in a week. Both tests were successful and seen as demonstrating the slow improvement of its nuclear arsenal.
Experts say atomic history—especiallythat of the U.S. program, the world’ s most successful, which other nations often seek to mi mic—can help distinguish North Korea’ s credible accomplishments from bluster and empty threats.
The nuclear age began in 1938 over a snowy Christmas holiday in Sweden when Li se Me it ne rand her nephew, Otto Fri sch, tried to make sense of a colleague’ s puzzling experiments on uranium. During a hike, the physicists sat on a tree trunk and discussed the unlikely possibility that its atoms had split in two.
Mei tn er knew Einstein’ s equation. She did a calculation estimating how much energy a split atom might release. Suddenly, all the experimental facts fell intoplace.
“It was beautiful ,” her biographer wrote .“Everything fit .”
The discovery, called nuclear fission, led to a global race to split heavy atoms in chain reactions. The fuel soft he first atomic bombs were either uranium or plutonium, both heavier than lead.
Soon, scientists found another way to free the hidden energy—by fusing two light atoms into one. The fuels were deuterium and tritium, rare forms of hydrogen. They were known as thermonuclear because their ignition required the blistering heat so fan exploding atomic bomb, which acted like a match.
Fusion—which powers the sun and the stars—turned out to release far more energy. It led to history’ s most powerful blasts as well as decades of super power brinkmanship with thousands of nucleararms.
The United States in 1951 injected a tiny amount of thermonuclear fuel into the core of anatomic bomb, boo sting its power. The explosion was roughly three times stronger than the Hiroshima blast.
What beckoned was the idea of installing near the atomic bomb a separate capsule that would hold much more thermonuclear fuel.
In 1954, on Bikini A toll in the Pacific, the United States tried that approach. The fire ball expanded for miles. The shock wave swept neighboring atolls clean of vegetation and animals. In minutes, the mushroom cloud rose some 25 miles. Slowly, its radio activity spread aroundtheglobe.
The destructive force of that single hydrogen device turned out to be far greater than all explosives used in World War II, including the atomic bombs dropped on Hiroshima and Nagasaki. Theblast,code-namedBravo,was1,000 times more powerful than the Hiroshimabomb. It was the nation’ s most violent thermonuclear test ever.
But as Einstein fore told, the amount of matter that Bravo converted into energy wasmind-bogglinglysmall—onthe order of 1,500 grams, or about 3 pounds.
Few experts think North Korea will get close to mastering the secrets of true hydrogen bombs anytime soon, if ever. But they cite a range of evidence suggesting that the isolatednation is now working hard to raise the destructive force of its nuclear arsenal with thermonuclear fire.
“It’ s possible that North Korea has already boosted ,” Gregory S. Jones, a scientist at the RAND Corp ., said of the first step down the thermonuclear road.
The prospect of the North making strides in missile stopped with nuclear arms that could threaten the United States has prompted the Trump administrationto increase pressure on Kim Jon gUn, the North’ s leader.
The world’ s first atomic bomb, the Gadget, tested in 1945 in the New Mexicandesert, had a fuel efficiency of less than 20 percent. Thereafter, over years and decades of experimentation, designerslearned how to raise the burn rate. Exactly how far is a federal secret.
The North, like most countries with nuclear ambitions, has followed the U.S. play book. The question is how much progress it has made since its first atomic test more than a decade ago.
Two detonations last year helped clarify the picture. The first, in January, was about as powerful as the Hiroshima blast. With typical swagger, the North declared it had detonated a hydrogen bomb—a claim experts universal ly rejected. The explosion was far too small.
Still, emerging clues suggested the North was indeed going down the thermonuclear road—particularly in enhancing its atomic bombs.
Experts found evidence that it had modified are actor to make tritium, built a plant that could gather up the radioactivegas, and produced a thermonuclear fuel ingredient in such abundance that it was selling it online.
“I think it’ s pretty clear they’ ve we a po ni zed and miniaturized ,” Bruce K ling n er, a former head of the CI A’ s
Korea branch, recently told a group in Washington.
The finding went to warheads for short-and-medium-range missiles able to hit mucho of Japan and South Korea. Experts say the North still has along way to go in perfecting warheads for its intercontinen ta lb all is tic missiles, none ofwhichhave under gone flight testing.
LastSeptember, the North set off another blast —its fifth. By some estimates, theexplosion was twice as strong as the Hiroshima bomb. That suggested its designershadused more atomic fuel, had achieved a hig her rate of burning, or had engagedinth hermonuclear boosting.
Albright of the Institute for Science andInternation al Security has argued for another possibility. The North, he says,maybe e pursuing an intermediate stageoftherm mo nuclear arms design knownaslayering.
In that step, weapon designers wrap alternatingla ayers of thermonuclear fuel anduraniuma round atomic bombs. Thatburnsmore hydrogen than simple boosting. When the Russians first tried thatapproach, Al bright noted in a recent report, the test device produced a blast over 25 times stronger than the Hi roshima bomb.
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