By Jung Sung-ki
Staff Reporter
North Korea's second nuclear test Monday indicated that the regime has improved its capacity to some extent since 2006, as it inches toward full membership in a club of unofficial nuclear-weapons states, most experts agreed Tuesday.
South Korean and U.S. authorities said that the test produced a 4.7-magnitude tremor at the northeastern site of North Korea's first nuclear test in October 2006.
Seoul believes the previous test registered 3.58 on the Richter scale, while Washington said it was magnitude 4.3.
Estimates of the size of the latest underground explosion in North Korea vary from 1 to 2 kilotons to as high as 10 to 20 kilotons. The higher estimate would match the power and potency of the bombs America dropped on Hiroshima and Nagasaki in 1945 to end World War II.
Russia estimated Monday its measurements reflected the higher range, while the United States downplayed it as a few kilotons of TNT.
Seoul's National Intelligence Service said Tuesday that the second test by the North was believed to have an explosive force four to eight times stronger than that of the first test. It also warned that Pyongyang could test-fire an intercontinental ballistic missile soon (ICBM).
A successful nuclear test is considered producing a yield of 5 to 15 kilotons. A kiloton is equivalent to 1,000 tons of TNT. Washington regarded the 2006 test as a failure, citing the explosion force of 0.8 kilotons.
``They're not anywhere as good as Israel, but they could probably deploy a weapon on top of a Nodong (Rodong) missile and be fairly confident that it would work,'' David Albright, a former nuclear inspector and president of the Institute for Science and International Security, was quoted by the Washington Times as saying.
Speculations have been high that North Korea may have produced nuclear warheads that could be carried by its short- and medium-range missiles that can cover all of South Korea and Japan.
The North is believed to have deployed more than 600 Scud missiles with a range of 320 to 500 kilometers and 200 Rodong missiles, with a range of 1,300 kilometers, near the inter-Korean border.
In 2006, Pyongyang test-fired a series of missiles off the eastern coast toward Japan, including a Taepodong-2 ballistic missile with a range of 6,700 kilometers, far enough to hit the United States with a light payload.
It is estimated that North Korea has about 30 to 50 kilograms of plutonium ― enough to make six to 10 nuclear bombs.