A mushroom cloud after the test of an atomic bomb. (U.S. Air Force/AP)

Just now, the fate of the summit between President Trump and North Korean dictator Kim Jong Un, which Singapore is expecting to host June 12, is uncertain. The South Korean president landed in Washington on Monday, hoping to smooth Trump’s ruffled feathers and convince him the summit should take place, despite Kim’s recent threats to cancel if the United States insisted on “unilateral nuclear abandonment.” Trump is reportedly reconsidering the meeting, fearing the summit will be a failure.

But there’s still some good news on the Korean Peninsula: North Korea is planning to publicly dismantle its Punggye-ri nuclear test site and described the move on Sunday as a “significant measure.” The North Koreans have invited some journalists to attend — and deciding not to miss a business opportunity, they are charging each journalist $10,000 in visa fees. 

Is the North Korean move significant — or symbolic?

Intelligence on North Korea is limited. The country may have hidden test sites that we don’t know about, and it could dig new test shafts at any point or refurbish the dismantled one, as researcher Jeffrey Lewis noted. It could conduct nuclear tests in the future, whether or not it dismantles this site.
Most important, North Korea may not need any more nuclear tests. It has conducted six so far, and as researcher Catherine Dill has explained, it may not require any additional data to design and miniaturize its nuclear bombs.

Certain nuclear designs are simpler than others and require very limited testing, if any.

Some basic nuclear weapons have such a simple design that they do not require any testing. The most famous example is the “gun type” design that was code-named Little Boy. Developed by Manhattan Project scientists during World War II, the design is essentially a closed-off cannon in which two pieces of highly enriched uranium are hurled against each other. Without being tested even once before being deployed, “Little Boy” destroyed Hiroshima on Aug. 6, 1945.

More-complicated designs called ‘implosion designs’ do need some testing — usually.

“Implosion designs” are trickier. Most of the time they require some testing, although experienced, advanced scientists who have external nuclear testing data might be able to forgo the tests.

In an implosion device, a sphere of fissile material (plutonium or highly enriched uranium) is pressured symmetrically until it explodes. The bomb that was used against Nagasaki, code-named Fat Man, was a plutonium-based implosion device; before using it, the United States did test it in New Mexico in the famous Trinity nuclear test before deployment. North Korea is believed to be developing plutonium-based implosion devices and possibly some that are uranium-based as well.

The Iranians were also thinking about implosion devices, but not with plutonium.

When Israeli Prime Minister Benjamin Netanyahu presented the Iranian nuclear archive documents captured by the Mossad, revealing details of the Iranian nuclear effort from 1999 to 2003, he showed documents with images of Iranian implosion designs, based on highly enriched uranium. The documents Netanyahu presented also discuss possible Iranian nuclear test sites.

 Overt nuclear tests are not crucial to certain nuclear programs.

Not all states possessing nuclear weapons opt to conduct “overt nuclear tests” — tests that are publicly declared or noticed by the international community. During the Cold War, Israel, Pakistan and South Africa had all used their willingness to refrain from overt nuclear tests as a bargaining chip when negotiating with the United States. In all three cases, the United States agreed to alleviate the pressure it was applying against nuclear development —  in return for a “do not surprise me with a test” guarantee.

Israel has never conducted an overt nuclear test, or indeed publicly commented on its nuclear capabilities, but some researchers say that the small country may have conducted a nuclear test in the Indian Ocean in September 1979.

During the 1980s, apartheid-era South Africa developed an untested arsenal of 6½ nuclear bombs, which President F.W. de Klerk ordered dismantled in 1989.

During the 1980s, Pakistan started developing a nuclear arsenal; its efforts continued through the decade without an overt test, although China may have hosted a test of a Pakistani device in 1990. Then in 1998, Pakistan conducted overt tests.

What does this tell us about North Korea’s missile effort and its intercontinental ballistic missile (ICBM) program?

Continued U.S. engagement with North Korea could yield benefits, even if Pyongyang refuses to fully give up its nuclear arsenal. As Mark Bell explained here at Monkey Cage, the United States could aim at such important goals as restricting North Korea’s nuclear program, preventing nuclear exports and clearing up communication channels.

Because the North Koreans have already managed to develop an ICBM, the United States obviously benefits simply by freezing the North Korean program. Western experts do not know whether the North Koreans have already managed to miniaturize a nuclear warhead and fit in on a missile — but if they have not done so yet, they are probably not very far behind.

Will the North Koreans agree to a deal that would ban them from doing so? If so, could this promise be verified? What would be the unintended consequences of such a deal on U.S. regional alliances with South Korea and Japan? It’s true that the continental United States would not be threatened by a North Korean nuclear (or thermonuclear) ICBM under such terms — but U.S. allies would still be threatened by shorter-range North Korean missiles. Would these missiles be fitted with nuclear warheads? Would these allies reconsider their security relationship with the United States or even consider developing nuclear-weapons capabilities of their own?

Dismantling North Korea’s test site is a positive step. But it is only the first one toward creating a safer Korean Peninsula.