We continue from  North Korea’s Miniaturized Nuke Part 1.

The Pakistan nuclear program had the benefit of many years of scientific exchange with the U.S. This created the intellectual depth required for design that, while not clean-sheet, was at least capable of some innovation. North Korea has not had this benefit. Open sources suggest that plans and parts were acquired directly from Abdul Qadeer Khan, “father” of the Pakistan program.

Since North Korea has had virtually no legitimate scientific contact with the outside world, the proliferation channel for miniaturized weapons may have been different. Khan’s transfer was many years ago. But the miniaturized warhead is new. This suggests another transfer source, with exploitation delayed relative to the transfers of Khan.

If you want to know a specific fact that happens to be hidden by an adversary, espionage and secret technical collections of the U.S. intelligence community are typically superior to open sources. We may not know for many years, if ever, how this presentation relates to the ultimate truth. Sometimes a phrase leaks here and there. Keep your eye out for “linear implosion.”

I’ve omitted the word “alleged” everywhere it should be used.

With the assumption that North Korea wanted the fastest path to a warhead, they chose replication, not independent design. Of the nuclear powers, the former Soviet Union was most accessible to illicit transfers. The easiest thing to transport is something with a handle on it.

Googling quickly leads to conspiracy theories and survivalist blogs. My contribution to the genre is North Korea’s Plutonium, Iran’s Uranium / Suitcase Nukes. The subject inspires so much fear that mainstream media recoils in the opposite direction. I’ve been searching for a quote of George Tenet,  in which he wonders why the mainstream dismisses the possibility. An example  is (ABC) Suitcase nukes closer to fiction than reality, It’s not deliberate manipulation, but contamination of objectivity by an attitude of denial. The alarmists take the most dire view, which is that the devices still exist, and still work.

Middlebury Institute offers a paper, “Suitcase Nukes:” A Reassessment. Quoting, “First, the probability that any portable nuclear devices were lost prior to or after the breakup of the Soviet Union appears low;…” A quick summary of the argument, which relies heavily on impugning  Alexander Lebedev and (NTI) Alexei Yablokov, the primary Russian sources:

• Lebedev and Yablokov have ulterior motives.
• The Russians can’t keep a secret. Existence  would have leaked.
• Never mind that Yablokov corroborates Lebedev.
• Never mind that the U.S. had the SADM.
• Ergo,  the claim that suitcase nukes exist is highly dubious.

The paper shows  that with a scholarly tone and a good bibliography, you can tilt the tables as much as a pinball player scrounging for nickels.

The one argument worth paying attention to is that they haven’t been used by terrorists, people with notorious inability to resist impulse. Now we can tighten the brackets formed by alarm and denial. They may exist, but don’t work anymore. A third source, Stanislav Lunev, is quoted (Wikipedia):

Stanislav Lunev, the highest-ranking GRU defector, claimed that such Russian-made devices exist and described them in more detail.[10] The devices, "identified as RA-115s (or RA-115-01s for submersible weapons)" weigh from fifty to sixty pounds. They can last for many years if wired to an electric source. In case there is a loss of power, there is a battery backup. If the battery runs low, the weapon has a transmitter that sends a coded message either by satellite or directly to a GRU post at a Russian embassy or consulate. According to Lunev, the number of "missing" nuclear devices (as found by General Lebed) "is almost identical to the number of strategic targets upon which those bombs would be used."[10]

Maybe you think these guys are a bunch of fakes. You have permission to dismiss one of the three. When asked about suitcases, a fourth,  retired General Vladimir Dvorkin, said (Frontline)

Not that I'm aware of. Both United States and Russia of course built tactical nuclear weapons that were quite small in size ... . We had, for example, what we called atomic demolition munitions, that were designed to be carried in a backpack. ... I doubt that there was ever anything that was specifically designed to be carried in something that looked like a suitcase, though I couldn't rule it out. 

Dvorkin’s denial that any military nukes are missing is quoted in (San Diego Union-Tribune) “How threat of loose Soviet nukes was avoided.” But his own reasons for certainty are weak. The article authors assert that if there were loose nukes, we would have seen some uses. But,

• Although Russian military nukes are not nearly as safe as ours, arranging for one to explode is not  trivial for a terrorist. And with a few years of waiting, the tritium goes stale.
• Nukes of all kinds would have been eagerly bought by Pakistan or North Korea, so the unaccounted would never reappear.
• The suitcase nukes were under the control of the KGB, not the military. With Soviet compartmentalization, Dvorkin might have not known.
• At the peak, in 1988. the Soviet Union had about 45,000 nuclear warheads.  It is down to about 7000. Not a single  RA-115 suitcase nuke has been volunteered by the Russians as having been destroyed. The Russian line is they never existed. So if they did exist, what happened to them?

So we’re down to the style of the style of luggage. This can be answered at the next Fashion Week. But can a roller-nuke outlast the zippers and wheels?

The statement has been made that the shelf life of Russian nukes is short compared to U.S. ones. This is not open source. But the basics are simple:

• Plutonium emits neutrons, which cause all kinds of materials to fall apart. Special materials, produced only by the U.S., can reduce this. Standard explosives are used, possibly with additive stabilizers.
• The plutonium itself tends to fall apart. Alloys help. Secret alloys may help more.
• Electronics  tends to fail. Spacing/shielding within the complete gadget is not adequate to prevent this.The problem extends to parts not normally thought of as sensitive. The U.S. makes rad-hard parts that others do not.
• The tritium in a boosted weapon, which these days means all of them, has to be periodically flushed and replaced.

But there are many ways to skin a cat. North Korea makes tritium. Lunev stated that the Soviet RA-115 could survive for many years. Semiconductors are not essential. Tubes have been used in the past, and some special types, like the sprytron, still are.

Suppose you have a few samples of a non-optimal, miniature implosion device, such as a Soviet RA-115. It’s non optimal because it uses linear implosion. But it gives you precise geometries, and you know that it worked. It may still work if  the tritium is flushed and the explosives are replaced. You might be able to scale it up a bit. Remember that everything about a North Korean rocket is a little shoddy. It’s heavier than it should be. The motor is not efficient. It’s not accurate. But it’s hardly the point to make a thing of beauty.

Is it?