Nuclear weapons have been available on the "black market" (thanks to sloppy soviet handling practices) for decades, yet no terrorist or criminal group has ever used a nuclear fission initiation device
Cite please. From Pinker's new book:
It’s really only nuclear weapons that deserve the WMD acronym. Mueller and Parachini have fact-checked the various reports that terrorists got “just this close” to obtaining a nuclear bomb and found that all were apocryphal. Reports of “interest” in procuring weapons on a black market grew into accounts of actual negotiations, generic sketches morphed into detailed blueprints, and flimsy clues (like the aluminum tubes purchased in 2001 by Iraq) were overinterpreted as signs of a development program.
Each of the pathways to nuclear terrorism, when examined carefully, turns out to have gantlets of improbabilities. There may have been a window of vulnerability in the safekeeping of nuclear weapons in Russia, but today most experts agree it has been closed, and that no loose nukes are being peddled in a nuclear bazaar. Stephen Younger, the former director of nuclear weapons research at Los Alamos National Laboratory, has said, “Regardless of what is reported in the news, all nuclear nations take the security of their weapons very seriously.”274 Russia has an intense interest in keeping its weapons out of the hands of Chechen and other ethnic separatist groups, and Pakistan is just as worried about its archenemy Al Qaeda. And contrary to rumor, security experts consider the chance that Pakistan’s government and military command will fall under the control of Islamist extremists to be essentially nil.275 Nuclear weapons have complex interlocks designed to prevent unauthorized deployment, and most of them become “radioactive scrap metal” if they are not maintained.276 For these reasons, the forty-seven-nation Nuclear Security Summit convened by Barack Obama in 2010 to prevent nuclear terrorism concentrated on the security of fissile material, such as plutonium and highly enriched uranium, rather than on finished weapons.
The dangers of filched fissile material are real, and the measures recommended at the summit are patently wise, responsible, and overdue. Still, one shouldn’t get so carried away by the image of garage nukes as to think they are inevitable or even extremely probable. The safeguards that are in place or will be soon will make fissile materials hard to steal or smuggle, and if they went missing, it would trigger an international manhunt. Fashioning a workable nuclear weapon requires precision engineering and fabrication techniques well beyond the capabilities of amateurs. The Gilmore commission, which advises the president and Congress on WMD terrorism, called the challenge “Herculean,” and Allison has described the weapons as “large, cumbersome, unsafe, unreliable, unpredictable, and inefficient.”277 Moreover, the path to getting the materials, experts, and facilities in place is mined with hazards of detection, betrayal, stings, blunders, and bad luck. In his book On Nuclear Terrorism, Levi laid out all the things that would have to go right for a terrorist nuclear attack to succeed, noting, “Murphy’s Law of Nuclear Terrorism: What can go wrong might go wrong.”278 Mueller counts twenty obstacles on the path and notes that even if a terrorist group had a fifty-fifty chance of clearing every one, the aggregate odds of its success would be one in a million. Levi brackets the range from the other end by estimating that even if the path were strewn with only ten obstacles, and the probability that each would be cleared was 80 percent, the aggregate odds of success facing a nuclear terrorist group would be one in ten. Those are not our odds of becoming victims. A terrorist group weighing its options, even with these overly optimistic guesstimates, might well conclude from the long odds that it would better off devoting its resources to projects with a higher chance of success. None of this, to repeat, means that nuclear terrorism is impossible, only that it is not, as so many people insist, imminent, inevitable, or highly probable.
Cite, please.
200 Soviet nukes lost in Ukraine -- article from Sept 13, 2002. There have been reported losses of nuclear submarines at sea since then as well (though those are improbably recoverable). Note: even if that window is closed now, it was open then, and no terrorist groups used that channel to acquire nukes -- nor is there, as your citation notes, even so much as an actually recorded attempt to do so -- in the entirety of that window of opportunity.
When dozens of disparate extremist groups failed to even attempt to acquire a specific category ...
Here's a poser that occurred to us over the summer, and one that we couldn't really come up with any satisfactory solution to. The people who work at the Singularity Institute have a high estimate of the probability that an Unfriendly AI will destroy the world. People who work for http://nuclearrisk.org/ have a very high estimate of the probability that a nuclear war will destroy the world (by their estimates, if you are American and under 40, then nuclear war is the single most likely way in which you might die next year).
It seems like there are good reasons to take these numbers seriously, because Eliezer is probably the world expert on AI risk, and Hellman is probably the world expert on nuclear risk. However, there's a problem - Eliezer is an expert on AI risk because he believes that AI risk is a bigger risk than nuclear war. Similarly, Hellman chose to study nuclear risks and not AI risk I because he had a higher than average estimate of the threat of nuclear war.
It seems like it might be a good idea to know what the probability of each of these risks is. Is there a sensible way for these people to correct for the fact that the people studying these risks are those that have high estimate of them in the first place?