One of the many things that keep me up at night — and anyone who thinks about the future of terrorism —  is the possibility of a nuclear detonation in New York or some other American city.  North Korea has a small arsenal of nuclear bombs, and tested one in October 2006. It did not explode; it merely fizzled, but perhaps its scientists have learned from the experience and future tests will be more successful. In any case, the cash-strapped country has both indicated and demonstrated a willingness to disseminate its nuclear technology to other rogue states, most recently, some evidence suggests, to Syria. (For a discussion of North Korean proliferation, see the pertinent section in this report issued by the Office of the Director of National Intelligence.)

Our own arsenal, of course, offers reason to worry, as the recent breakdown in control revealed in the Broken Arrow incident of last August makes clear. But the problem is of a different order of magnitude; preventing mishaps is vitally important, but the possibility of an authorized detonation, either deliberately or by accident, appears to be close to nil.

In response to my recent post on the surety of U.S. nuclear weapons, one of my sources in Washington pointed me to a Pentagon document summarizing dozens of accidents with U.S. nuclear weapons that occurred in the period 1950-1980.

The bad news is that even when great care is exercised, major accidents have happened. The good news is that even when these fearsome devices are subjected to unexpected shocks and the heat generated in fiery airplane crashes and the detonation of their high-explosive triggering devices, the nuclear core of these babies has never once exploded.�