Blast hints at North Korea’s nuke

The amount of energy discharged from a nuclear bomb recently tested by North Korea may show the device used plutonium, which would mean the country hasn’t yet found the other route to the weapon, according to an arms-control expert.

North Korea on Feb. 12 announced its third test of a nuclear device. The underground detonation has escalated tensions in the region. The U.S. flew pairs of stealth aircraft over South Korea, including F-22 fighter jets and nuclear-capable B-2 bombers, in a show of force. The North threatened retaliation and on April 2 pledged to restart a closed reactor to boost production of the weapons material.

North Korea has steadily increased the explosive power, or yield, of its nuclear tests, to six to seven kilotons in February, from about two kilotons in 2009 and from less than a kiloton in 2006, according to a Feb. 12 report from the Congressional Research Service. The first two are believed to have used plutonium rather than highly enriched uranium. Obtaining the fissile material is the main hurdle in building a nuclear weapon.

“It looks more as if they’re sort of gradually improving a design that they’ve been working on,” said Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, an arms-control organization based in Washington that supports the reduction of nuclear weapons. “You could argue and say, ‘Well, maybe it’s more likely a plutonium device versus them starting all over on a totally new design based on uranium.'”

Still, because so little is known about North Korea’s activities, “it could go either way,” he said in a telephone interview. “We really don’t know one way or the other.”

The U.S. successfully pursued both paths to the bomb during the Manhattan Project in the 1940s, Kristensen said. Early tests of U.S. nuclear weaponry yielded about 15 and 20 kilotons, he said. India and Pakistan’s first atomic devices yielded about 10 to 12 kilotons, he said.

The difference in yields suggests Pyongyang is “still not very good at producing this,” Kristensen said.

A third test of a plutonium-based bomb would also diminish North Korea’s stockpile of the weapons-grade material. The country is estimated to have between 30 and 50 kilograms of separated plutonium, enough for four to seven weapons, according to the CRS report.

While North Korea has acknowledged a uranium enrichment program, it previously said its purpose was to produce fuel for nuclear power. That may have changed under the regime of Kim Jong Un, which last month called for bolstering its nuclear weapons production.

North Korea’s latest atomic test, along with its December launch of a satellite into orbit using a Taepo Dong 2 rocket and recent display of an intercontinental ballistic missile, demonstrates a “commitment to develop long-range missile technology that could pose a direct threat to the United States,” James Clapper, director of National Intelligence, said in prepared remarks last month to the Senate Intelligence Committee.

North Korea probably won’t have the capacity to attack the U.S. with nuclear missiles “for many years,” and its ability to strike South Korea is very limited, according to Siegfried Hecker, a Stanford University professor and former Los Alamos National Laboratory director who has repeatedly traveled to the country to report on its nuclear facilities.

“Nevertheless, this is an uneasy situation with a potential for miscalculations from a young and untested leader,” he said in an April 2 article from Stanford’s Center for International Security and Cooperation.

About the Author

Brendan McGarry
Brendan McGarry is the managing editor of He can be reached at Follow him on Twitter at @Brendan_McGarry.
  • STemplar

    I bet the writers of South Park are trying to do an episode, but with the amount of looney coming from them they have to keep erasing and revising the script.

    Interesting stuff from inside China where the internet sites are apparently ripping the Norks and calling what’s his nuts ‘fatty kim’. The suspension of the editor guru for the editorial in which he called for abandoning the Norks. I think we should continued with measured responses and let them continue their mental spin out. Seems to be working in our favor with Chinese public opinion.

  • Davis

    Well it’s good to hear North Korea cannot strike the US and has only limited capabilities in striking S. Korea but their continuation of nuclear and missile testing clearly shows their intentions. Hopefully, the Kim regime will collapse before they go full nuclear with ICBM’s.

  • Musson

    How about we unilaterally draw down our own stock of nuclear weapons? I am sure that the NORKs and Iranians would follow our lead and renounce atomic weapons if we just show them the way.



      I doubt that. Until there are government changes in both countries, they have no reason to yield on their nuclear weapons. Both countries think that the world is against them; and its is pretty much true. The only way nukes will leave Tehran and Pyongyang is by war or some extensive talks and treaties. They won’t abandon.

    • orly?

      Its called the “START” (STrategic Arms Reduction Treaty).

      We’ve been drawing down our stockpiles since 1991.


        Albeit slowly. I don’t think that we will ever need nukes, at least on Earth. Cold War ended a while back. I say pack ’em up, and if outfit them on spacecraft. Even thought its illegal.

    • Mitch S.

      Looks like you have to make it clearer you’re being sarcastic than just a “/s”.

      • Musson


    • Kim

      Could this be called ‘reverse trolling’?

      • whatever

        are you the great leader from North Korea?

        what does ‘reverse trolling’ mean? define it please.

    • whatever

      Musson, if the US wants other countries to renounce nuclear weapons, it should renounce them first, not merely draw down the stock.

  • anonymous

    Keep beating those war drums. It worked so well for Iraq.


    Ok, NK does not pose a threat to mainland USA. Simple truth. Their “missiles” would be detected minutes after launch. And missile defense will take care of them. Also, this is assuming that these missiles get past the boost phase of launch, and have the ability to target, well, anything. Finally, whatever missile they want to wave at the US, it doesn’t have a nuclear weapon duck (or is it duct) taped to the tip. They don’t have the technology, and it will most likely stay that way unless Russia and China go back to freely backing NK, which is the opposite of what we have seen both parties do. No matter what happens, I sense that there will be a MASSIVE dispute on this article. Man, where are those Palestinian monkeys?

  • superraptor

    Japan and South Korea hopefully will move forward to quickly develop their own nuclear deterrence. The US has become militarily weak and unreliable

  • brad

    I want to believe that China has to understand that if North Korea manages to stock pile a few nukes, then it will pose an actual threat to China also.

  • Tribulationtime

    A few questions to share. How can Little Big Kim (aka The Great Leader) save the face?. Someone Knows What F…king Shht NKorea wants?. How do affect this crisis to Iran affair?. What if Nkorea bombs damaged nuclear power central in Japan? Can China afford a bridgehead in the peninsula without Nkorea buffer?. Do a Tactical Nuke bring International Green Light to attack Iran?. I can´t foresee the future but i very sad why i feel this time war gonna re-start. I hope the whole thing don´t exceed operations in DMZ and near around.

  • Taylor

    North Korea working with Iran, so the Iranians could have purchased a plutonium nuke already and could probably test their own weapon designs in North Korea to maintain the cover that they are not pursuing nuclear weapons.

  • Skyler the Weird

    Let’s call North Korea Austria-Hungary. The PRC is Imperial Germany. the US is the British Empire. They will back their Ally cause there is no way their number one trading partner will go to a world war with them for backing an inavasion of Serbia/South Korea.


      I don’t think you can compare this to WWI or WWII. WAY to many variables to deal with that. Just stick to what it is. If SK is attacked, US will go in. If SK attacks, notice now I am saying that SK is doing the attacking, then the US will back them up, but not as readily. Either way, NK will have US fighters and bombers flying over it, and US naval ships in its waters.

  • Simple Man

    That’s all we need. Nuclear proliferation.

    South Korea, and particularly Seoul, would bear the brunt of the damage, from artillery fire mainly.

    Our own missile defense system is in question as the results have not been spectacular. But at the same time deception is critical to success. Let’s hope that if they do launch we can knock them down without detonating them.


      Detonating what? That hasn’t been answered. NK missiles CAN NOT launch a nuclear warhead. A) it doesn’t have the thrust requirements. B) Even if it could (which it can’t), the nukes they are making aren’t that powerful.

  • Mikey

    It’s my hope that before Fat Kim can do anything rash, the Generals will step in and kick his *&# . This kid is about as smart as a bowl of soup. At least the Generals have got some brains between their ears. Fat Kimmey is trying to keep hold of Daddies country. And he’s not very good at it.


      Ehmm. No, the won’t give Kim the boot, as he is basically a god to NK. And the Generals are just as bit as crazy as Kim-jong-un, if not more so.

  • Engineer

    Ok – this has stopped being funny. Time for us to get the Chinese on board and tell them they need to make their boy Kim to go away – he is bad for business – Chinese Business!

  • Speedy


  • todd

    I think we will soon take out NK’s nuclear and ICBM program and stockpiles. Possibly even regime-change. SK has already begun pursuing nuclear weapons, with other regional countries likely to eventually follow. This nuclear proliferation is a long-term threat to US and everyone. If you doubted our policy on denying Iran nuclear weapons, because of the Mideast nuclear arms race that would ensue, what’s happening in Asia, with SK (and soon others) considering/asking for/pursuing nuclear weapons technology, is vindication. I think we need to shut it down. All the US steps thus far seem like a logical progression in that direction.

  • blight_

    Clearly people need some re-education about the Democratic People’s Republic of Korea and the titles of greatness that come with its hilarious leaders.

    It goes (Great Leader->Eternal President), (Dear Leader->Great Leader->Eternal Leader),(Brilliant Comrade->Great Successor->?)

    Wonder if the Great Successor will make it to Eternal Successor.

    And some bomb targets. You know, for…defense.


      I just call them all foolish fat fellows.

  • Benjamin

    With Russian diplomats being told to look at evacuating by Pyongyang, things do not look to well.
    My thinking is that these missiles ( being readied will actually be sent on a trajectory to overflight Japan and maybe Guam. Either way, we are going to be forced to attempt to intercept them.