Hans M. Kristensen in Federation of American Scientists Strategic Security Blog:
The world’s approximately 23,300 nuclear weapons are stored at an estimated 111 locations in 14 countries, according to an overview produced by FAS and NRDC.
Nearly half of the weapons are operationally deployed with delivery systems capable of launching on short notice.
The overview is published in the Bulletin of the Atomic Scientists and includes the July 2009 START memorandum of understanding data. A previous version was included in the annual report from the International Panel of Fissile Materials published last month…
Israel probably has about four nuclear sites, whereas the nuclear storage facilities in India and Pakistan are – despite many rumors – largely undetermined. All three countries are thought to store warheads separate from delivery vehicles.
Despite two nuclear tests and many rumors, we are unaware of publicly available evidence that North Korea has operationalized its nuclear weapons capability.
Warhead concentrations vary greatly from country to country. With 13,000 warheads at 48 sites, Russian stores an average of 270 warheads at each location. The U.S. concentration is much higher with an average of 450 warheads at each location. These are averages, however, and in reality the distribution is thought to be much more uneven with some sites only storing tens of warheads.
More here. [Thanks to Kris Kotarski.]