Questions raised by North Korea’s nuclear test (VIDEO)

PYONGYANG, Sept 10 — North Korea said yesterday it has successfully tested a miniature nuclear warhead that could be put on a missile, raising concern about how close it is to having a credible weapon.

A sales assistant watches TV sets broadcasting a news report on North Korea's fifth nuclear test, in Seoul, South Korea, September 9, 2016. — Reuters pic
A sales assistant watches TV sets broadcasting a news report on North Korea's fifth nuclear test, in Seoul, South Korea, September 9, 2016. — Reuters pic

Here are four questions about the North’s fifth nuclear test, which at an estimated 10 kilotons is its most powerful to date.

How big?

With a force of 10 kilotons, or the equivalent of 10,000 tons of TNT according to South Korea’s meteorological agency, the blast was smaller than the atomic bomb that destroyed Hiroshima in August 1945. That bomb had a force of around 15 kilotons and killed 140,000 people, half of whom died immediately.

A November 2011 study funded by the US government determined that the Severe Damage Zone (SDZ) from a 10-kiloton warhead over Washington would measure almost a mile (1.6 kilometres) in diameter. Within that space, few buildings would remain standing, “and few people would survive.”

IHS Janes analyst Karl Dewey noted that such a warhead would “be capable of ripping the heart out of a city.”

How small is miniature?

Miniature refers here to the size of a warhead small enough to fit on a ballistic missile, making it a much more dangerous threat.

North Korea says it has now succeeded in doing just that, but the claim has not been confirmed by an outside source.

The technological challenge is huge, but Pyongyang seems determined to meet it, at which point it could conceivably arm ballistic missiles able to reach neighbours in Asia and possibly the United States.

The difference between ‘A’ and ‘H’

Atomic or “A-bombs” work on the principle of nuclear fission, where energy is released by splitting atoms of enriched uranium or plutonium encased in the warhead. Hiroshima was destroyed by one A-bomb with a uranium-fuel warhead. Nagasaki was destroyed three days later by a plutonium A-bomb of similar power, 17 kilotons.

The United States and the Soviet Union then designed much more powerful warheads dubbed hydrogen or “H-bombs.” Also known as thermonuclear bombs, they work on the principle of fusion of two nuclei, and generate temperatures similar to those found at the sun’s core. When an H-bomb is detonated, chemical, nuclear and thermonuclear explosions succeed each other within milliseconds. The nuclear explosion triggers a huge increase in temperature that in turn provokes the nuclear fusion. The largest such blast took place in October 1961 when the Soviet “Tsar Bomba” exploded in the Arctic with a force of 57 megatons, or 57,000 kilotons.

Unlike its last test in early January, North Korea’s state media did not speak this time of a hydrogen warhead. While no H-bomb has been used in a conflict so far, the world’s nuclear arsenals are comprised for the most part of such weapons.

“Most of the thermonuclear warheads in service today have so-called ‘dial-a-yield’ options that allow for low explosive yields (less than 10 kilotons),” notes Shannon Kile of the Stockholm International Peace Research Institute (SIPRI).

Who has nuclear weapons?

Britain, France, China, Russia and the United States, the five permanent members of the UN Security Council, officially have nuclear weapons.

India and Pakistan also have operational nuclear weapons, while Israel maintains a policy of nuclear ambiguity. North Korea appears to be close. — AFP