North Korea's May nuclear test few kilotons: U.S.

reuteurs ^ | 6/15/09 | reuteurs

[Flavius]

WASHINGTON (Reuters) – The United States has determined that the nuclear test conducted by North Korea last month yielded an explosion of a few kilotons, the U.S. Office of the Director of National Intelligence said on Monday.

"The U.S. intelligence community assesses that North Korea probably conducted an underground nuclear explosion in the vicinity of Punggye on May 25, 2009," the office said in a statement. "The explosion yield was approximately a few kilotons."

North Korea's first nuclear test, in 2006, was about one kiloton.

Shortly after this year's blast, Russia said it estimated the explosion at about 20 kilotons, or about equal to the U.S. atom bomb dropped on Nagasaki in Japan in World War Two.

[NonValueAdded]

I think this was asked and answered before but ... is not a small yield test an indication of greater sophistication than if they just lit off a Hiroshima-style nuke?

[Tuketu]

Who are you going to believe. The Russkies or our lying, peace (piece) making at any price government?

[handy old one]

A nuke is a nuke weather it is the size of the ones that hit Japan or the size of a small marble it will do some damage You don’t want to be around when it goes off.

[Aglooka]

In 2006 the DPRK stated the yield would be 4kt. This was stated before the test.

A "few kilotons" would mean their design is working close to what is predicted.

And another thing. No one has any way to prove the can't put this in a warhead right now.

[Quickgun]

You are right about that, and, where there is a small nuke, there is likely to be a large one, in my opinion. NK is very dangerous, the country is not prospering, and that alone makes them dangerous. We need to remember that human life is not held in high value in a lot of countries that are our potential enemies,or we will be rudely reminded of that fact one day.

[JasonC]

No. It indicates a "squib", a fizzle. The bulk of the reacting plutonium (and uranium tamper) is blowing apart, out of the central core of the explosion, before it has time to release its full energy. This is caused by a failure of the implosion lense. Instead of a spherical compression of the fissile material, it is "venting" asymmetrically.

Getting the conventional implosion to concentrate the reacting mass as efficiently as possible is technically and mathematically difficult. It requires a precise timing by high-speed switches to ignite the conventional explosive around the reactive material, and a shaped arrangement of that charge in different thicknesses of different types of explosive, to precisely "focus" the imploding material on a small sphere at the core of the bomb.

Understand, as the nuclear reaction spikes, it opposes this inward pressure wave. Both neutrons and gamma rays released in the core at striking the infalling material and dumping their energy into it, slowing its collapse. The neutrons can travel farther into the material before hitting anything, since they do not react with the electron shells of the matter around the core, but only hit something when and if they hit an atomic nucleus.

John von Neumann did the math for the implosion lense back in the 1940s, and everyone else on earth, since, has cribbed his answers instead of working it out against for themselves. OK, a few US and Russian scientists working on fusion weapons were also competent to do it (Teller, Sakharov e.g.). But it is far from trivial.

Also understand that a simple gun-type bomb of the Hiroshima rather than the Nagasaki design can dispense with this step, but only by using a much larger amount of uranium instead of a smaller amount of plutonium. It is not possible to shrink a gun-type warhead for missile delivery. Those can't be made under 4 tons or so. All smaller deliverable warheads (by anything other than a large manned bomber I mean) rely on a plutonium implosion design and require mastering the implosion lense. It is easily the hardest single step in making a *deliverable* nuclear weapon.

[penelopesire]

It took them a whole MONTH to figure it out?

*sigh*

[Centurion2000]

Good summary.

[Cindy]

Note: The following text is a quote:

http://www.dni.gov/press_releases/20090615_release.pdf

OFFICE OF THE DIRECTOR OF NATIONAL INTELLIGENCE
PUBLIC AFFAIRS OFFICE
WASHINGTON, D.C.
20511

NEWS RELEASE

FOR IMMEDIATE RELEASE ODNI News Release No. 23-09
June 15, 2009

STATEMENT BY THE OFFICE OF THE DIRECTOR OF NATIONAL INTELLIGENCE
ON NORTH KOREA’S DECLARED NUCLEAR TEST ON MAY 25, 2009

“The U.S. Intelligence Community assesses that North Korea probably conducted an underground nuclear explosion in the vicinity of P’unggye on May 25, 2009. The explosion yield was approximately a few kilotons.
Analysis of the event continues.”

# # #

[Cindy]

Previously...

http://www.freerepublic.com/focus/news/2257577/posts

“Magnitude 4.7 - NORTH KOREA [Update - underground nuclear test]”
United States Geological Survey ^ | May 24, 2008
Posted on May 24, 2009 7:19:11 PM PDT by Strategerist

[calex59]

I think this was asked and answered before but ... is not a small yield test an indication of greater sophistication than if they just lit off a Hiroshima-style nuke?

I want to know exactly, what is a "few Kilotons". Also in answer to your question: I believe some people have said they are trying to get them small enough to fit on a missile and that the small explosions reflect that. A 4 KT bomb would destroy the centers of any large US city and kill thousands and maybe millions with loss of service and fall out(radation depends on how high they explode the bomb, ground bursts produce more radiation, air bursts less).

Tell the people in Hawaii or Alaska that a missile with a "few" kt is coming and not to worry and see what they say!!!

[NonValueAdded]

Thanks for that answer. But couldn’t they test the explosive lenses all day long before a dress rehersal with fissile material?

[JasonC]

Until you have the radiation pressure of the critical-mass core pushing back, you don't face the actual conditions of the event.

The neutrons pass right through plasma, but heat the uranium tamper surrounding the whole shebang. The gamma rays strip off every electron from the incoming matter-wave until it is all pure ionized plasma. Then they hit the free electrons in that soup - all dumping their energy at short range.

The heating of the tamper outside, the momentum of the wavefront before the core gets going pushing back, and the short-range push-back of the gamma radiation, all matter.

It isn't a trivial calculation...

[JasonC]

If the previous still wasn't clear, remember this is about balancing forces to hold the core intact and concentrated as long as possible, for the maximum amount of fission to take place within it. Eventually the power of the fissioning core will overwhelm all other factors and blow everything apart violently. But when? Delaying the onset of that eventual winning-out, "just so", that is the trick of it...