Scientific checking on North Korea’s claim to have tested an H-bomb

SCIENCE CAN TELL IF NORTH KOREA’S TEST WAS REALLY AN H-BOMB,Wired,  7 Jan 16, “……North Korea has a history of exaggerating its military claims to achieve its political ends. (South Korea, the US, and Japan are typically named…… because North Korea’s leader Kim Jong Un is unlikely to let international inspectors anywhere near the test site, the only real way to tell whether North Korea’s big boom was the big H is by analyzing data collected from a suite of global sensors……

 “normal” atomic bombs rely solely on fission—that is, splitting an atom (typically plutonium or enriched uranium), which releases a bunch of energy and creates a big boom. Big enough to level the Japanese cities of Nagasaki and Hiroshima in 1945, killing over 200,000 civilians and military personnel.

Hydrogen bombs, on the other hand, use nuclear fusion—melding atoms together—to release way more explosive energy. These “thermonuclear” weapons are so powerful that they actually need atomic fission to kickstart the fusion process. That’s right, H-bombs use an A-bomb just to get going. American scientists detonated the first H-bomb in 1952, on a Pacific atoll. It was over 500 times more powerful than the bomb the US dropped on Nagasaki. Modern H-bombs are at least twice as powerful. Which is why everyone is so freaked out about whether North Korea, the world’s most famous renegade nation, has a hydrogen bomb…….

why seismologists take recordings from multiple sensors. The agency responsible for monitoring atomic blasts, the Comprehensive Nuclear-Test-Ban Treaty Organization, currently has 42 certified seismic stations distributed around the globe (plus over 100 auxiliary stations). Because seismic signals bounce through the Earth, not only did Russia and Japan pick up North Korea’s event, but so did the US……….

The smoking gun can only really come by detecting radioactive material. To that end, CTBTO has radionuclide detection stations scattered throughout the globe. These come in two flavors. The first looks for radioactive dust—fallout. These systems use suction pumps to pull air through a filter, which then goes through a radiation counter. The types of particles present, and their radioactivity, would give a lot of clues as to the bomb’s type. Let’s say you have a typical atom bomb: Its fallout particles would be decayed bits of uranium or plutonium.

A hydrogen bomb also uses those materials, but they’d be mostly burned away by the super hot fusion reaction. According to this 1991 analysis of a Chinese explosionpublished in Science and Global Security, an H-bomb’s radioactive particulate signature would have a lot less decayed plutonium and uranium, and also different ratios of their various decayed isotopes. But if someone knew the exact particles found after an H-bomb went off, they could use that knowledge to build their own H-bomb (that’s probably one of the ways the Soviets copied the US’s weapon). Which is why Wallace told me the details of the analysis are secret. But if the blast is underground, as this one seems to have been, radionuclide detection is little help—the particles get contained.

The other type of detector looks for radioactive gases, rather than particles. Xenon gas is the most potent of these, partly because it is a noble gas that doesn’t interact with other substances. Xenon can, however, decay. And the rate of decay tells scientists the gas atoms’ exact age. For instance, after North Korea’s 2013 test, a Japanese sensor picked up xenon isotopes that scientists deduced were exactly 55 days old. The exact same day as North Korea’s test…….

it matters not just what kind of bomb North Korea detonated, but that the country detonated one at all.


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