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更新时间:2017-4-15 23:23:26 来源:纽约时报中文网 作者:佚名

North Korea May Be Preparing Its 6th Nuclear Test

New satellite images suggest that North Korea might soon conduct another underground detonation in its effort to learn how to make nuclear arms — its sixth explosive test in a decade and perhaps its most powerful yet.


North Korea’s nuclear tests have grown steadily more destructive, and the country continues to pursue its longtime goal of putting a nuclear warhead on an intercontinental missile capable of reaching targets around the globe.


The United States recently ordered an aircraft carrier and other warships toward the Korean Peninsula in a show of force intended to discourage the North from testing a nuclear weapon.


While examining satellite imagery, experts have observed a wide range of activity at Mount Mantap, a mile-high peak where North Korea conducts its nuclear tests. Beneath the mountain, a system of tunnels has been excavated for the past five detonations of the North’s nuclear bombs.


North Korea often marks significant dates with shows of military force, and analysts say it might detonate a nuclear weapon to celebrate the birthday this Saturday of the nation’s founder, Kim Il-sung, the grandfather of the current leader, Kim Jong-un.

朝鲜经常通过展示军事力量来纪念重要日子。分析人士表示,本周六,它可能会引爆一个核武器,来庆祝开国领袖金日成(Kim Il-sung)诞辰。金日成是现任领袖金正恩(Kim Jong-un)的祖父。

Big debris pile suggests the possibility of a much larger detonation.


Since late 2013, piles of rocky debris from the excavation of the site’s North tunnel system have grown quite large — now big enough to cover a football field, and quite high. It’s the largest pile ever observed there. Work on the excavation has recently slowed, quite likely signaling readiness for the next detonation.


So too, observers of the test site have recently noted a lot of water being pumped out of the North tunnel system – presumably to prevent washouts and keep it dry for test instrumentation. Groundwater is often a problem in tunneling as it can slow progress, weaken structures and cause shorts in electrical gear.


Scientists at the Los Alamos weapons lab who have studied images of the large debris pile recently concluded that Mount Mantap could withstand a nuclear explosion of up to 282 kilotons – roughly 20 times stronger than the Hiroshima blast. Previously, the largest detonations were in the Hiroshima range.

前不久,研究这些大型瓦砾堆图像的洛斯阿拉莫斯(Los Alamos)武器实验室的科学家得出结论,万塔山能够承受高达282千吨的核爆炸,大约比广岛爆炸的破坏力大20倍。之前最大威力的爆炸都和广岛爆炸同一级别。

No one outside of North Korea knows for sure what could take place or how big the blast might be. It’s a guessing game — though a sophisticated one for Washington’s intelligence agencies, and less so for civilians armed only with unclassified information. Either way, it's a detective story full of clues, questions and a protagonist with a clear motive.


Experts in satellite imagery, military analysts around the world, and geologists and physicists track progress at the remote site mainly through the observation of tunneling, building construction, truck movements and, though harder to see, personnel moves.


Seismic activity helps pinpoint North Korea’s detonations.


Mount Mantap is the world’s only active nuclear test site. Most other nuclear states long ago gave up such explosions in a coordinated effort to end arms races and their dangerous and costly spirals of military action and reaction.


In North Korea, the test devices are buried deep inside tunnels bored through solid rock far below Mount Mantap’s peaks, creating field labs for nuclear experiments. The nearest major city, Chongjin, is situated about 50 miles to the northeast.


The tunnels for the North’s tests are excavated just over halfway up Mount Mantap, which rises to a height of 7,234 feet. The bomb is placed at the end of the tunnel, which gets partly backfilled to prevent radioactive leakage, and then detonated in the test.


To pinpoint the geographic site of the nuclear blasts, experts rely on the kind of seismologic data used to track earthquakes. Similarly, each of the North’s detonations has generated shock waves that register around the globe.


Experts say the North’s tunnel system will quite likely play a significant role in future testing because it is the busiest area at the Punggye-ri nuclear test site, has a conspicuous perimeter fence and has the largest amount of protective rock directly overhead.


Several independent teams, including ones from China, South Korea, Norway and the United States, have gathered seismic readings from the North’s bomb tests. In addition, a world body known as the the Comprehensive Test Ban Treaty Organization, based in Vienna, Austria, operates a sprawling network of global sensors.

中国、韩国、挪威和美国等国的几个独立团队收集了朝鲜核炸弹试验的地震级数。此外,奥地利维也纳的一个被称为全面禁止核试验条约组织(Comprehensive Test Ban Treaty Organization)的世界性机构在全球范围内布置了一个庞大的传感网络。

Last year, a team of South Korean scientists confirmed a test’s exact location within Mount Mantap by studying data from a radar satellite that detected subtle elevation changes on the mountain’s surface.


So far, North Korea’s nuclear tests have grown more destructive.


The North has shown technical savvy in pacing its nuclear tests to increase the amount of time for bomb makers to conduct detailed analyses of the blasts and learn from mistakes.


“They’ve done five tests in 10 years,” said Siegfried S. Hecker, a Stanford professor who once directed the Los Alamos weapons laboratory in New Mexico, the birthplace of the atomic bomb. “You can learn a lot in that time.”

“他们在10年内完成了5次试验,”斯坦福大学(Stanford University)教授西格夫里·S·赫克(Siegfried S. Hecker)说。他曾是原子弹诞生地新墨西哥州洛斯阿拉莫斯武器实验室的主任。“在这么长时间里,你可以学到很多东西。”

In contrast, he added, India and Pakistan conducted a rush of nuclear detonations in May 1998 in what experts called a blitz of saber rattling. “They couldn’t have learned much,” Dr. Hecker said.


North Korea may be focused on increasing the power and range of its nuclear weapons.


North Korea’s past tests are thought to have centered on mastering a simple type of atomic bomb, known as an implosion device.


Some of the tests may have featured “boosted” atomic bombs, however — meaning that an injection of tritium, a radioactive form of hydrogen, could have increased their destructive power. All such fuels, known as thermonuclear, need the high heats from an exploding atom bomb for ignition.


“It’s possible that North Korea has already boosted,” said Gregory S. Jones, a scientist at the Rand Corporation who analyzes nuclear issues. Like other experts, he pointed to the nation’s two nuclear detonations last year as possible tests of small boosted arms.

“可能朝鲜已经进行了加强,”兰德公司(RAND Corporation)分析核问题的科学家格雷戈里·S·琼斯(Gregory S. Jones)说。和其他专家一样,他也认为朝鲜去年的两次核爆可能是在试验小型的加强核武。

As signs of the North’s interest in boosting, experts cite modifications to a reactor that could make tritium, as well as construction of a plant that could gather up the radioactive gas. Boosted arms can raise the destructive power of atomic blasts or greatly reduce their need for atomic fuel. That savings can significantly lighten and shrink the resulting arms, making them easier to hurl over long distances. Boosting is considered a main step to scaling down warheads so they can fit atop intercontinental missiles.


Nine countries possess nuclear arms, most having advanced over time from making simple atom bombs to advanced hydrogen bombs. Nuclear experts say North Korea’s program is at an intermediate phase of development — somewhere between stages one and three. The secret to achieving more destructive power is to raise the amount of thermonuclear fuel that an exploding atom bomb can ignite.


Experts say the likelihood of North Korea making strides in its nuclear program has risen with the recent evidence that the nation tried to sell excess lithium-6, which is the main ingredient for making thermonuclear fuels, including tritium.


So too, satellite images of the mountainous test site reveal the digging of the deep tunnel system, which could allow the detonation of a larger device.


A gathering at the remote site is considered a strong sign.


On March 28, a satellite image showed people gathered in front of an administrative building at the test site. The last time such a large group was observed was on Jan. 4, 2013, a little more than a month before North Korea’s third nuclear detonation.


Experts see the recent gathering as yet another sign that the North may be getting closer to detonating a device in its increasingly long series of nuclear tests.


“The fact these formations can be seen suggests that Pyongyang is sending a political message that the sixth nuclear test will be conducted soon,” wrote Joseph S. Bermudez Jr., and Jack Liu, experts at 38 North, an analysis group that closely tracks North Korea. “Alternatively, it may be engaged in a well-planned game of brinkmanship.”

“我们能够看到这些集结本身表明,平壤正在释放一个政治信号:第六次核试验将很快进行,”密切关注朝鲜的研究组织38 North的专家小约瑟夫·S·贝穆德斯(Joseph S. Bermudez Jr)和杰克·刘(Jack Liu)写道。“或者,它可能在进行一个精心策划的边缘策略游戏。”