Abstract
Pakistan, which has a nuclear arsenal of about 60 nuclear weapons, is busily enhancing its nuclear weapons capabilities. In the last five and a half years, Pakistan has deployed two new nuclear-capable ballistic missiles and is readying a third, entered the final development stages of a potentially nuclear-capable cruise missile, started construction of a new pluto-nium production reactor, and is close to completing a second chemical separation facility.
Pakistan's nuclear weapons program began in earnest after India's “peaceful” nuclear explosion in May 1974. Over a 20-year period, at what is now known as the Abdul Qadeer Khan Research Laboratories in Ka-huta near Islamabad, Pakistan pursued a method using gas centrifuges to enrich uranium to produce the fissile material for its nuclear weapons. By the end of the 1980s, with assistance from Canada, China, and France, Pakistan had the capability to rapidly assemble a nuclear device if necessary. A moratorium on the production of highly enriched uranium (HEU) was declared in 1991, but production soon resumed. In late May 1998, Pakistan responded to India's nuclear tests by conducting a small number of nuclear explosions over two days. Seismic measurements of the May 28 and 30 tests suggest that the yields were 9-12 kilotons and 5 kilotons, respectively–lower than what the Pakistani government claimed. 1 Pakistan's first nuclear warheads used an implosion design with a solid core of HEU rather than plu-tonium, likely requiring 15-20 kilograms of HEU per warhead.
Like other nations that have developed nuclear weapons, Pakistan does not seem content with a first-generation nuclear weapon that uses HEU; it has been pursuing plutonium-based designs for at least a decade. Its 40- to 50-megawatt heavy water Khushab plutonium production reactor, completed in 1998 at Joharabad in the Khushab district of Punjab, is surrounded by six surface-to-air missile batteries to protect against air strikes. Pakistan is building a second heavy water reactor at the Khushab site, which will more than double its plutonium production capability. Our best estimate of the size of the new reactor is that it will be in the 40- to 100-megawatt range. 2
Plutonium separation takes place at the “New Labs” reprocessing plant next to the Pakistan Institute of Nuclear Science and Technology at Rawalpindi, Pakistan's original chemical separation facility. A 300-megawatt reactor (Chasnupp-1) was completed at Chashma in 1999, and a new chemical separation facility there is nearing completion. Close by is a fuel fabrication plant. 3 The reactors provide the Pakistani military with several options: fabricating weapons that use plutonium cores, mixing plutonium with HEU to make composite cores, or using tritium to “boost” the warheads' yield (loading the reactors' targets with lithium 6 will produce tritium).
These efforts suggest that Pakistan is preparing to increase and enhance its nuclear forces in the coming years, especially if it attempts to match India's ambitious plans to deploy a nuclear triad of aircraft and land- and sea-based missiles. It is difficult to estimate precisely how many nuclear weapons Pakistan has produced and what types they are, and it is equally troublesome to guess what its future plans might be. In 1999, the U.S. Defense Intelligence Agency estimated that Pakistan had 25-35 nuclear warheads. 4 The Institute for Science and International Security's David Albright, a nongovernmental expert who tracks the global amounts of fissile material, estimates that Pakistan had produced 40 kilograms of plutonium and 1,100 kilograms of HEU by the end of 2003–enough, by his measure, for about 60 warheads. 5
The precise amount of plutonium or uranium needed for a bomb depends upon two variables: the technical capabilities of the scientists and engineers, and the desired yield. The higher the capability, the less material is needed, while the higher the yield, the more material is needed. We do not know the skill level of Pakistani bomb designers, but an average technical capability certainly seems plausible. Pakistan's weapons are probably 5-10 kilotons by yield, judging by its few tests. We assume that warhead production has continued since 2003, and with the deployment of two new weapon systems anticipated in the next few years, we estimate a current Pakistani nuclear stockpile of about 60 warheads.
The F-16s most likely to have been modified to carry nuclear weapons are deployed with Squadrons 9 and 11 at Sargodha Air Base (AB), 160 kilometers (100 miles) northwest of Lahore. The F-16 has a refueled range of more than 1,600 kilometers (1,000 miles), more if drop tanks are used. It can carry up to 5,450 kilograms externally on one under-fuselage center-line pylon and six underwing stations. The F-16s with nuclear missions in NATO can each carry up to two B61 nuclear bombs, but Pakistan's F-16s most likely carry a single bomb on the centerline pylon because its weapons are probably heavier than the B61.
Sargodha AB's weapons storage area has igloos but lacks the extra security features that would indicate storage of nuclear weapons. Given this, the assembled nuclear bombs and/or bomb components for the F-16s may be kept at the large Sargodha Weapons Storage Complex 10 kilometers (6 miles) south of Sargodha. An alternative possibility is that, fearing a first strike by India if war were to break out, Pakistan stores its weapons at other operational or satellite bases west of Sargodha, where the F-16s could disperse to pick up their bombs.
Pakistan's Arsenal, 2007
We estimate that Pakistan has approximately 60 nuclear warheads for these delivery vehicles.
Missile payloads may have to be reduced to achieve maximum range. Aircraft range is for illustrative purposes only; actual mission range will vary according to flight profile and weapon loading.
Under development.
The Ghaznavi entered service in 2004. The solid-fueled, single-stage missile can deliver a 500-kilogram payload to approximately 400 kilometers (250 miles). It is believed to be derived from the Chinese M-11 missile, of which approximately 30 were delivered to Pakistan in the early 1990s. The Ghaznavi is launched from a four-axle, road-mobile transporter-erector-launcher (TEL); Pakistan deploys fewer than 50 launchers for it. Some Ghaznavis are thought to be deployed at the Sargodha “Weapons Storage Complex, which has 12 missile garages. A Ghaznavi was test-launched on December 9, 2006, from an undisclosed location in what the Pakistan Army's Strategic Force Command described as “the culmination phase of the training exercise, which validated the operational readiness of the Strategic Missile Group (SMG) equipped with Ghaznavi missiles.” 6
Pakistan's Shaheen-1 (“eagle”) is a reverse-engineered M-9 missile originally supplied by China. The solid-fueled, single-stage missile has been in service since 2003, can strike targets in excess of 450 kilometers, or 280 miles (some say 700 kilometers, or 435 miles), and can deliver a pay-load of up to 1,000 kilograms. It is carried on a four-axle, road-mobile TEL similar to the one that carries the Ghaznavi, and like the Ghaznavi, fewer than 50 launchers are deployed for it. The Shaheen-1 was last test-launched on November 29, 2006.
Islamabad claims that its two-stage Shaheen-2 medium-range ballistic missile, unveiled seven years ago at the Pakistan Day parade but still under development, has a range of 2,500 kilometers (1,555 miles) and can carry a 1,000-kilogram pay-load. It is carried on a six-axle, road-mobile TEL, and satellite images of the National Defense Complex near Fatehjang show 15 TELs at various stages of being equipped with their missile erector. A Shaheen-2 was test-launched February 23, 2007, to a range of 2,000 kilometers (1,240 miles).
Rumors about one or more extended-range versions of the Ghauri appear to have been mistaken. U.S. Air Force intelligence overviews from 2003 and 2006 do not list new Ghauri missiles under development.
Footnotes
1.
Pakistan announced that it tested five nuclear devices on May 28 and one on May 30. But seismic records do not discriminate the May 28 tests, and it is possible that only one device was detonated that day. See Robert S. Norris and William M. Arkin, “Known Nuclear Tests Worldwide,” Bulletin of the Atomic Scientists, November/December 1998, p. 65.
2.
Thomas B. Cochran, “What Is the Size of Khushab II?” Natural Resources Defense Council, September 8, 2006. The estimate of up to 1,000 megawatts made by David Albright and Paul Brannan in “Commercial Satellite Imagery” is too large. See more on their calculations in Institute for Science and International Security, “Commercial Satellite Imagery Suggests Pakistan is Building a Second, Much Larger Plutonium Production Reactor: Is South Asia Headed for a Dramatic Buildup in Nuclear Arsenals?” July 24, 2006; William J. Broad and David E. Sanger, “U.S. Disputes Report on New Pakistan Reactor,” New York Times, August 3, 2006, p. 6; Shahzeb Jillani, “Pakistan Nuclear Report Disputed,” BBC News, August 7,2006.
3.
David Albright and Paul Brannan, “Chash-ma Nuclear Site in Pakistan with Possible Reprocessing Plant,” Institute for Science and International Security, January 18,2007.
4.
“A Primer on the Future Threat” (Secret), in Defense Intelligence Agency, The Decades Ahead: 1999-2020, July 1999, p. 38. Reprinted in Rowan Scarborough, Rumsfeld's War: The Untold Story of America's Anti-Terrorist Commander (Washington, D.C.: Regnery, 2004), pp. 194-223.
5.
Institute for Science and International Security, Global Stocks of Nuclear Explosive Ma-teriah, chap. 1, “Summary Tables and Charts,” July 12,2005 (revised September 7,2005), p. 6.
6.
“Pakistan Tests Nuclear-Capable Ballistic Missile,” Agence France-Presse, December 11, 2006.
7.
Paul Garwood, “Pakistan Test-Fires Cruise Mssile,” Associated Press, March 21,2006.
