Joshua PollackNorth Korea’s Nuclear Test That Wasn’t

Monday, the wonk world was briefly aflutter with the news reported by the Chosun Ilbo: a radionuclide detection station in South Korea had caught a strong whiff of xenon, whose radioactive isotopes are the products of nuclear fission.

The Chosun’s correspondent even suggested that the xenon spike, which took place in mid-May, might have something to do with North Korea’s announcement of an unspecified achievement in fusion technology:

On May 14, two days after the North’s announcement, air analysis of KINS’s radiation detection station in Geojin, Gangwon Province showed about eight times as much xenon as in ordinary times, a government official said. “Authorities concerned have concentrated on analyzing this,” he added.

(Readers may recall that the alleged fusion breakthrough supposedly took place in mid-April.)

Perhaps needless to say, a fusion reaction doesn’t produce fission products. Chosun quoted an unnamed expert who seemed to be suggesting that North Korea might have tested a boosted device — a fission bomb with a small touch of fusion — which brings to mind some of Jeff’s recent speculations. But the South Korean government shortly ruled out a nuclear test, observing that there had been no unusual seismic activity.

Let’s also observe that there was no announcement. Pyongyang has never been shy about sharing the news of a nuclear test with its own people or with the world. That’s sort of the point: to demonstrate capability. And, as I observed back in February, the North Korean government has lately become much more concerned with signaling its ability to deliver food and consumer goods than big rockets and earth-shaking blasts.

Where the Xenon Came From

There are a handful of other ways that some excess radioactive xenon could have found its way to South Korea’s skies.

One possibility is the production of medical isotopes. But it doesn’t appear that there’s a facility big enough and close enough to have caused the spike.

A second possibility is a reprocessing facility, like North Korea’s “radiochemistry laboratory” at Yongbyon. Pyongyang claims to have finished its last reprocessing campaign there last year, but it’s possible that they were bluffing until recently.

Unfortunately for this theory, even if the plant had been operating in May 2010, the spent fuel would have aged too much to release much xenon. The half-lives of its radioisotopes are counted in hours or days. So scratch that idea.

The last important possibility is a nuclear reactor of one sort or another. It seems that whenever a reactor is started up or the pressure vessel is opened for refueling, gases escape, including xenon. A typical light-water reactor is refueled annually. And given all the power reactors across the Far East, that probably happens around there with some regularity.

All that’s really required to explain the unusual reading at Geojin is for a reactor startup or opening to have occurred within hundreds of miles in the previous week or so. Heck, if you want a specific candidate, Japan’s Monju breeder reactor was restarted on May 6.


  1. Anne Bazuin (History)

    Portugal – North Korea 7 -0


  2. FSB

    It could also be a reactor failure in N. Korea leading to Xe release. (eg. Windscale)

  3. Rwendland (History)

    Remember that, as Sig Hecker reported in 2008, the Yongbyon reprocessing facility has a large stock of high-level radioactive waste from recent campaigns (~80 cubic meters in 2008) that needs to be treated and disposed of. Hecker said that would have to be done within a year or two. Could starting on this, or even just venting tanks or transfering it, release xenon?

  4. Rob (History)

    I was about to say the same thing Anne, but I also saw a great YouTube clip where North Korea are World Champions:

  5. Anon

    I’d be curious what isotopes of Xe they detected as well as if anyone has done any meteorology backtracking. There were plenty of tests in Europe on radioxenon sensors (for the CTBTO) that detected xenon in higher concentrations than expected. The story goes that every reactor kept pointing to the one “upstream” when they were asked about it…

  6. Carey Sublette

    Currently speculation about a DPRK boosted weapon seems based simply on the assumption that they would probably want one. The DPRK mention of fusion research could mean almost anything – simply producing fusion reactions in a laboratory is a very low hurdle to clear.

    Two issues that a DPRK boosting project would have to contend with is getting tritium (they would seem to have no domestic source) and how much nuclear testing they can afford given their limited plutonium supply. A successful boosted design could lower their plutonium requirement for each weapon and offset this of course.

    Collaboration with another country, like Pakistan, which could supply tritium on a boosted design might be quite attractive (while we are idly speculating).

  7. CB (History)

    Another possibility is a strategic deception. Intentionally vent some xe recovered from prior operations to drive the west crazy trying to figure out what happened. It is a good way to keep everyone guessing as to what the real nuclear capabilities are. If I was in their place, and didn’t really have a working bomb, but had a lot of isotopes sitting around as a result of documented efforts, a deceptive release would perpetrate the myth that I had real technology instead of a pile of radioactive stuff.

  8. George William Herbert (History)

    There are industrial users of Xenon as well; it could be an industrial release. Isotopic analysis, particularly Xe-133 and Xe-135 would help disambiguate…

  9. Gridlock (History)

    I heard the Dear Leader can actually choose which Noble Gas he wishes to exhale.

  10. Allen Thomson (History)

    Would one expect detectable amounts of Kr-85 to be present along with Xe-133/135 from a reactor discharge?

  11. CF

    Great photo of classic Xenon pinball – brought a smile to my face (I own this machine). Just wanted you to know your choice of graphics is also appreciated along with the wonk commentary!

  12. Josh (History)


    Thanks for saying so! Weapons of mass destruction can be a surprisingly dull topic, so it always helps to enliven things with illustrations, videos, etc., whenever possible. Missiles on cows. That sort of thing.

    By the way, does the pinball cabinet art strike you (as it does me) as echoing the poster art for Fritz Lang’s Metropolis?

  13. kme

    Josh: Oh, most definitely.