Possible two-stage hydrogen bomb seen 'game changer' for North Korea

SEOUL, Sept 3 (Reuters) - North Korea's claim of a successful hydrogen bomb test marks a major step in the isolated country's long-stated goal of developing a nuclear-tipped missile that puts the U.S. mainland within range, experts say.

North Korea conducted its sixth and most powerful nuclear test on Sunday, which it said was a successful detonation of an advanced hydrogen bomb, technically known as a two-stage thermonuclear device.

All of North Korea's six nuclear tests including the one on Sunday have taken place at its underground testing site in Punggye-ri, deep in mountainous terrain, and it is hard to independently verify the claims.

But experts who studied the impact of the earthquake caused by the explosion - measured by the U.S. Geological Survey at magnitude 6.3 - said there was enough strong evidence to suggest the reclusive state has either developed a hydrogen bomb or was getting very close.

The detonation produced 10 times more power than the fifth nuclear test a year ago, South Korean and Japanese officials said. NORSAR, a Norwegian earthquake monitoring agency, estimated the yield at 120 kilotons, significantly above the 15 kiloton "Little Boy" bomb dropped on Hiroshima and the 20 kiloton "Fat Man" dropped on Nagasaki at the end of World War Two.

9 PHOTOS
Kim Jong-Un inspects hydrogen bomb
See Gallery
Kim Jong-Un inspects hydrogen bomb
North Korean leader Kim Jong Un provides guidance on a nuclear weapons program in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang September 3, 2017. KCNA via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong Un provides guidance on a nuclear weapons program in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang September 3, 2017. KCNA via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. TPX IMAGES OF THE DAY
North Korean leader Kim Jong Un provides guidance on a nuclear weapons program in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang September 3, 2017. KCNA via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. TPX IMAGES OF THE DAY
People walk past a street monitor showing North Korea's leader Kim Jong-Un in a news report about North Korea's nuclear test, in Tokyo, Japan, September 3, 2017. REUTERS/Toru Hanai
TOKYO, JAPAN - SEPTEMBER 03: Pedestrians walk past a monitor showing an image of North Korean leader Kim Jong-Un in a news program reporting on North Korea's 6th nuclear test on September 3, 2017 in Tokyo, Japan. South Korea, Japan and the U.S. detected an artificial earthquake from Kilju, northern Hamgyong Province of North Korea. State news agency KCNA announced Pyongyang have successfully carried out a test of a hydrogen bomb, which could be loaded to the Intercontinental Ballistic Missile (ICBM) missile. (Photo by Tomohiro Ohsumi/Getty Images)
Residents look up at a big video screen on Mirae Scientists Street in Pyongyang showing the image of a document signed by North Korean leader Kim Jong-Un to carry out a hydrogen bomb test on September 3, 2017. North Korea declared itself a thermonuclear power on September 3, after carrying out a sixth nuclear test more powerful than any it has previously detonated, presenting President Donald Trump with a potent challenge. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
Residents watch a big video screen on Mirae Scientists Street in Pyongyang showing newsreader Ri Chun-Hee as she announces the news that the country has successfully tested a hydrogen bomb on September 3, 2017. North Korea declared itself a thermonuclear power on September 3, after carrying out a sixth nuclear test more powerful than any it has previously detonated, presenting President Donald Trump with a potent challenge. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
Residents react as they watch the televised annoucement on a big video screen on Mirae Scientists Street in Pyongyang that the country has successfully tested a hydrogen bomb on September 3, 2017. North Korea declared itself a thermonuclear power on September 3, after carrying out a sixth nuclear test more powerful than any it has previously detonated, presenting President Donald Trump with a potent challenge. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

"That scale is to the level where anyone can say (it is) a hydrogen bomb test," said Kune Y. Suh, a nuclear engineering professor at Seoul National University.

"North Korea has effectively established itself as a nuclear state. This is not just a game changer, it's a game over," Suh said.

North Korea claims its intercontinental ballistic missiles (ICBMs) tested twice in July can reach large parts of the mainland United States.

But experts say it likely achieved that potential range only by topping the test missile with a payload lighter than any nuclear warhead it is currently able to produce.

Pyongyang is also yet to prove that any warhead it places on a long range-missile can survive re-entry into the earth's atmosphere after an intercontinental flight.

Developing a hydrogen bomb would be key to have a lighter warhead, because that would offer much greater explosive yield relative to size and weight.

"Getting this high of a yield would likely require thermonuclear material in the device," said David Albright, a physicist and founder of the non-profit Institute for Science and International Security in Washington.

"It would show that their design, whatever the specific design, has achieved a yield that is capable of destroying modern cities."

Albright, however, still questioned the North's claim that it was a genuine two-stage thermonuclear device.

North Korea said in January 2016 that it tested a miniaturized hydrogen bomb. But outside experts said it was likely a "boosted" device, meaning an atomic bomb which uses some hydrogen isotopes to create bigger yield.

10 PHOTOS
Kim Jong Un's chemistry briefing
See Gallery
Kim Jong Un's chemistry briefing
North Korean leader Kim Jong-Un looks on during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un looks on during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un looks on during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un gives field guidance during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un looks on during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un gives field guidance during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un smiles during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. FOR EDITORIAL USE ONLY. NO THIRD PARTY SALES. SOUTH KOREA OUT.
North Korean leader Kim Jong-Un gives field guidance during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
North Korean leader Kim Jong-Un gives field guidance during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on August 23, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS.
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

TWO-STAGE REACTION?

A hydrogen bomb usually uses a primary atomic bomb to trigger a secondary, much larger explosion.

Such a weapon, with the first stage based on nuclear fission - splitting atoms - and the second on nuclear fusion, produces much more power than traditional atomic bombs, or "pure fission" devices.

Hours before the latest test, North Korean state media published photographs of leader Kim Jong Un inspecting a peanut-shaped device that it said was a hydrogen bomb designed to be loaded on a new ICBM.

The elongated shape of the device shows a marked difference from pictures of the ball-shaped device North Korea released in March last year, and appears to indicate the appearance of a two-stage thermonuclear weapon, experts said.

"The bomb North Korea showed today, if you look at the shape, the front part looks like an atomic bomb which triggers nuclear fission and the back part, a second stage that generates nuclear fusion reactions," said Chang Young-keun, a rocket science expert at the Korea Aerospace University.

Once nuclear fusion is started, fast neutrons are created which once again trigger nuclear fission of uranium inside the bomb.

"This means explosions can happen double and triple. And that's why its power is great. Even if it's the same size and weight, if it's a hydrogen bomb, its power can be tens or hundreds times bigger," Chang said.

North Korea's Nuclear Weapons Institute said Sunday's test verified the functioning of a hydrogen bomb, including the "fission to fusion power rate and all other physical specifications reflecting the qualitative level of a two-stage thermo-nuclear weapon," according to the official KCNA news agency.

For the first time, North Korea also specifically mentioned the possibility of a electromagnetic pulse, or EMP, attack. Such a strike would involve detonating a bomb in the atmosphere, instead of firing a long-range missile at a major U.S. city.

Some U.S. policymakers and experts have raised concerns about such an attack, which could cause a massive power surge and deal a devastating blow to U.S. electric grid and critical infrastructure.

(Additional reporting by Soyoung Kim and Jane Chung in Seoul, David Brunnstrom in Washington, Editing by Soyoung Kim and Raju Gopalakrishnan)

Read Full Story

Sign up for Breaking News by AOL to get the latest breaking news alerts and updates delivered straight to your inbox.

Subscribe to our other newsletters

Emails may offer personalized content or ads. Learn more. You may unsubscribe any time.