Size matters for North Korea's nukes
By Matthew Rusling
WASHINGTON - While the full extent of North Korea's nuclear capabilities
remains unknown, the blast from this week's test was slightly more powerful
than the previous detonation, experts said.
Perhaps even more foreboding is that the test will enable North Korea -
internationally condemned for its fledgling nuclear program - to build on the
lessons learned and further improve its nukes, according to analysts.
Estimates based on seismographic data of the May 25 test's yield currently lie
between 2 and 20 kilotons. Russian and South Korean estimates range from around
10 kilotons to 20 kilotons.
In Richter scale measurements, the test was 4.52, compared to
4.1 in the first test in 2006, announced the Comprehensive Nuclear Test Ban
Treaty Organization in a statement.
This data suggest the detonation was roughly the size of the Fat Man - the bomb
dropped on Nagasaki in 1945. And while that explosion may pale in comparison to
Russian and US capabilities, North Korea's engineers are learning from each
test, gaining a wealth of technical data and information on performance and
design, said Rodger Baker, director of East Asia analysis at Stratfor, a global
intelligence company.
Charles Ferguson, Senior Fellow for Science and Technology at the Council on
Foreign Relations, said the test likely boosted the bomb makers' confidence
that their weapons can produce reliable nuclear yields. Michael O'Hanlon,
senior fellow at the Brookings Institution, said, "The first test [in 2006]
fizzled, and this one apparently did not. So they seemed to have fixed
something and now the whole world will know."
Even a one-kiloton device such as the one detonated in 2006 could be
devastating. "One kiloton would do about one-fifth the damage of the Hiroshima
bomb," O'Hanlon said. "It could easily kill 20,000 to 40,000 people."
Ferguson said it would be especially deadly in a densely populated city such as
Seoul. The radioactive fallout could be intense if the explosion occurred near
or at ground level, but less so if exploded high in the atmosphere. The
radiation would be most severe about 48 hours after the explosion but could
linger for several months at significant levels, he said.
Baker said it remains unknown just what kind of yield North Korean scientists
were aiming for last week, or whether scientists there are using a smaller or
larger device. If bomb makers started out with a larger device and only
achieved a smaller yield, they would have missed their target, he said. But if
they are working on something small from the start, that would indicate a
successful test.
Whatever the size, there are significant challenges in transitioning from a
crude nuclear device to one that can actually be delivered, Baker said. Simply
detonating a bomb does not signal that Kim Jong-il has the power to decimate
New York, Seoul or Tokyo by the flick of a switch, he said. Even loading a bomb
onto one of its H-5 light bombers - North Korea's heaviest combat aircraft -
would present difficulties, he said.
Paul Walker, director, security and sustainability of Global Green USA, an
anti-proliferation organization founded by former Soviet president Mikhail
Gorbachev, said North Korea's bombs are probably the bulky, clunky sort dropped
on Japan which weighed more than 10,000 pounds each. United States forces
struggled for months to fit them onto planes, which sometimes crashed during
test runs because they had to practice carrying equally weighted "dummy" bombs.
As for the type of design North Korea is working on, Baker said it is likely an
"implosion" weapon - a device triggered when smaller explosions crush a
plutonium-filled ball inside the bomb - similar to the Fat Man. That design is
tricky and requires perfect timing, something scientists in North Korea have
not likely mastered yet, but have probably improved during the last two years.
"You have to have lots of conventional explosives go off at exactly the same
time, and exactly the same distance to trigger the plutonium," he said.
Another challenge could be facilities, as North Korea may not even have the
proper underground chamber to test anything but the most rudimentary nuclear
weapon, Walker said. Testing a high-powered bomb - with a yield of more than a
megaton, for example - requires an underground cavern at least a half-mile in
diameter, Walker said. If the facility is too small, a blast could cause an
earthquake, he added.
The 2006 test showed that North Korea's test caverns are only large enough to
test a relatively small device, as a portion of the explosion broke through to
the surface and emitted radiation, he said.
North Korea's long-term goal may have more to do with a bomb's size than its
yield. Experts said North Korea may want to "miniaturize" a bomb and mount it
to a ballistic missile that can hit Seoul, Tokyo or even North America. But
this is likely beyond North Korea's current capabilities as it took the US more
than a decade after World War II to do so, Walker said.
"We didn't miniaturize until the 50s and 60s, so it may take another decade for
North Korea to do that," he said.
Still, for an enterprising adversary, there are a number of creative ways -
other than a missile head - to deliver a nuclear bomb to Japan or South Korea,
Walker said. "They could deliver something in crude guerrilla fashion - like a
fishing boat or speedboat," he said.
Baker said that while this is possible, it is not probable, as many ports
worldwide installed radiation scanners at ports after the September 11, 2001,
attacks on New York and Washington. Moreover, the world has fixed a watchful
eye on North Korea; virtually every boat departing from a North Korean harbor
is picked up by satellites.
North Korea is the only nation in the world to test a nuclear weapon - not
once, but twice - in the 21st century. It is likely to continue as a part of
its "150 days" economic campaign - an effort from now until October to rally
the population in the run-up to the 100-year anniversary in 2012 of Kim
Il-Sung's birth.
"I expect another test before October," Baker said.
Matthew Rusling is a Washington DC-based journalist who has spent several
years working in East Asia.
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