Decodificaci´on de m´axima verosimilitud

While significant efforts have been made to shore up nuclear supplies and unsecured materials, and the proliferation of nuclear technology have become a significant problem over the last decade. Access to nuclear experts, critical materials, and facilities has become a real possibility for a terrorist group. Worldwide hundreds of locations hold nuclear weapons or weapons grade material222 _{(but due to the secrecy of} these facilities, the exact number is unknown). One Congressional report on terrorism by the Congressional Research Service warned that terrorists could “obtain HEU from the more than 130 research reactors worldwide that use HEU as fuel.”223 _{As of 2007, an}

estimated four out of five research reactors used to produce HEU for civilian use lacked adequate security to protect against sophisticated thieves, while only around one-third of HEU-fueled research reactors have had all their HEU monitoring removed.224_{The report}

noted that the nations of “greatest concern as potential sources of weapons or fissile material” are widely thought to be Russia and Pakistan.225 _{Terrorists will obtain} plutonium or HEU wherever the combination of their strength and the security system’s weakness makes it easiest to steal.226

221 _{U.S. Library of Congress, Congressional Research Service, Weapons of Mass Destruction: The}

Terrorist Threat, 112–113.

222 _{The Belfar Center for Science and International Affairs, Nuclear Terrorism Threat Assessment,} April 12, 2010 as cited in Mowatt-Larssen, Islam and the Bomb, Religious Justification for and Against

Nuclear Weapons, 16.

223 _{Ibid.; U.S. Library of Congress, Congressional Research Service, Weapons of Mass Destruction:}

The Terrorist Threat.

224 _{Tanya Ogilvie-White, “Facilitating Implementation of Resolution 1540 in South- East Asia and the}

South Pacific,” in Implementing Resolution 1540: The Role of Regional Organizations, ed. Lawrence Scheinman (New York: United Nations Institute for Disarmament Research, 2008).

225 _{Dafna Linzer, “Nuclear Capabilities May Elude Terrorists, Experts Say,” Washington Post,} Wednesday, December 29, 2004, A1.

226 _{Matthew Bunn, “Nuclear Terrorism: A Strategy for Prevention,” in Going Nuclear: Nuclear}

Proliferation and International Security in the 21st Century, ed. Michael E. Brown, Owen R. Coté, Jr.,

In 2009, the global stockpile of HEU was about 1,600,000 kg, enough for more than 60,000 nuclear weapons; the global stockpile for (separated) plutonium (Pu) was about 500,000 kg., which is also sufficient for more than 60,000 weapons.227

So far, the majority of illicit trafficking cases where “plutonium” was offered for sale actually involved sealed radioactive sources, other radioisotopes, or even non- radioactive materials. Only two known cases involved dangerous forms of plutonium. In May 1994, 6.2 grams of plutonium of suspected military origin was found in the garage belonging to a businessman in Tengen, Germany, and in August 1994, 363 grams of mixed plutonium-uranium oxide (MOX) powder were seized from smugglers at the Munich International Airport upon their arrival from Moscow.228

Recorded thefts of nuclear materials appear in open source literature. The IAEA released data from its Illicit Trafficking Database that confirms 15 cases of nuclear trafficking in 2008 alone.229 _{The IAEA has also reported 1,266 incidents of illicit} trafficking over the last 12 years. These incidents involved 99 countries and included 18 incidents involving special nuclear highly enriched uranium or plutonium trafficking.230 However, analyzing HEU and plutonium trafficking is challenging because credible information on key aspects of nuclear trafficking investigations is not always available, and because a concern exists that not all such events have been detected by authorities.231

Despite terrorists’ known interest in acquiring nuclear materials for building a nuclear weapon, so far, however, no open source evidence links terrorist organizations

227 _{Global Fissile Materials Report 2009, International Panel on Fissile Materials, October 2009, 4.} 228 _{NTI Global Security Newswire, Illicit Trafficking in Weapons-Useable Nuclear Material: Still}

More Questions Than Answers, December 11, 2011.

229 _{Data from the IAEA Database. Also Matthew Bunn, “Securing the Bomb 2010,” reports 18 cases} of HEU theft. According to research by Matthew Bunn, over 18 documented cases of highly enriched uranium (HEU) have occurred, which is the essential ingredient needed to construct a nuclear weapon.

230 _{Jasbir Rakhra, “Nuclear Terrorism: Overlooked at the NPT, RevCon,” Eurasia Review, June 17,} 2010.

231 _{Center for Nonproliferation Studies, NTI Global Security Newswire, “Illicit Trafficking in} Weapons-Useable Nuclear Material: Still More Questions Than Answers,” December 11, 2011, http://www.nti.org/analysis/articles/illicit-trafficking-weapons-useable-nuclear-material-still-more- questions-answers.

with the known cases of illicit trafficking in HEU or plutonium.232 _{However, what} known cases of stolen or recovered material do show is that weapons-useable nuclear material, and especially HEU, remains in illicit circulation from thefts that presumably occurred in the 1990s. Therefore, this HEU should be considered potentially available for terrorists, possibly in the quantity sufficient for the production of a crude nuclear explosive device.233

The diffusion of scientific and technical information regarding the assembly of nuclear weapons has increased the risk that a terrorist organization in possession of sufficient fissile material could develop its own nuclear weapon. The complete production of a nuclear weapon strongly depends on the terrorist group’s access to fissile material and scientific expertise, which may come in the form of black market proliferators, or technical knowledge gathered from nuclear experts involved in a national nuclear program.234

1. HEU vs. Plutonium—The Preferred Terrorist Ingredient

HEU and plutonium are the two types of special nuclear material (SNM) needed to make nuclear weapons, and are the key ingredients terrorists would need and most likely seek to construct a possible IND.

Uranium mined from the ground must be extensively processed, or enriched before it can be considered weapons-grade material.235 _{Plutonium occurs naturally only} in trace amounts, and therefore, must be produced in a nuclear reactor.236 _{The capability} to create either HEU or plutonium capabilities “from scratch” are widely considered beyond the capability of even the most sophisticated terrorist;237 _{therefore, the common}

232 _{Center for Nonproliferation Studies, NTI Global Security Newswire, “Illicit Trafficking in} Weapons-Useable Nuclear Material: Still More Questions Than Answers.”

233 _Ibid.

234 _{U.S. Library of Congress, Congressional Research Service, Weapons of Mass Destruction: The}

Terrorist Threat, 4.

235 _{Levi, On Nuclear Terrorism, 15.}

236 _{Ibid. Also, of note, to use plutonium in nuclear weapons or nuclear fuel, however, it must be} separated from the rest of the spent fuel in a reprocessing facility.

belief is that terrorists would most likely try to attempt to acquire material from existing stockpiled sources through the diversion, theft or purchase on the black market. HEU exists in much greater quantities, and is used for both weapons and energy programs, which is why it is thought to be the primary desired target for terrorists and explains many of the existing policies intended to secure HEU stockpiles. HEU was termed by one report as the “Holy Grail” of terrorists.238

The amount of HEU needed to make a nuclear weapon varies with the degree of enrichment and the sophistication of the weapon design. In general, the higher the enrichment level, the less HEU is needed to make a bomb.239 _{For a HEU-based nuclear} weapon, two basic design options exist, a “gun-type” weapon where two pieces of HEU are brought together quickly and explode, and an “implosion weapon,” where a sphere of HEU is rapidly compressed in a highly symmetrical manner. Gun-type weapons are far simpler in design and could likely be built by some terrorist groups. The second is more difficult technically but requires less HEU.240 _{Plutonium-based nuclear weapons only} work as implosion weapons, with more sophisticated weapons using less plutonium.241

Open source estimates vary but “The Global Fissile Missile Report” estimates that only 25kg of HEU or 8kg of HEU are required to create one crude nuclear bomb.242

238 _{The term “Holy Grail” was used to in relation to HEU in Peter Zimmerman and Jeffrey Lewis,} “Bomb in the Backyard,” Foreign Policy, October 10, 2006.

239 _{Technical Note: The amount of HEU or plutonium sufficient for the production of one nuclear} explosive device could be different, depending on their nuclear properties. For example, a greater amount of uranium enriched to 80% 235U would be needed more than uranium enriched to 90% 235U. IAEA has introduced a term significant quantity (SQ), which is defined as “the approximate amount of nuclear material for which the possibility of manufacturing a nuclear explosive device cannot be excluded.” For plutonium containing less than 80% 238Pu, it is 8 kg, and for uranium, whose content of 235U is equal or more than 20%, it is 25 kg (See International Atomic Energy Agency, “IAEA Safeguards Glossary, 2001

Edition, International Nuclear Verification Series No. 3,” 2001, http://www-pub.iaea.org/MTCD/

publications/PDF/nvs-3-cd/PDF/NVS3_prn.pdf).

240 _{Also, proliferation-significant cases are defined as involving kilogram-level quantities of}

plutonium-239 or HEU with an enrichment level of 80% or more. At least 3 kilograms of plutonium-239 or 25 kilograms of HEU enriched to 80% or more would be required to build a nuclear bomb. In principle, a nuclear bomb could also be built with uranium enriched to less than 80%. The lower the enrichment level, however, the greater the quantity of uranium required. For instance, at 20% enrichment, about 200 kilograms of uranium or more, would be needed to build a bomb. A bomb maker would also need to understand very advanced techniques to be able to use uranium enriched to about 20 percent. Ferguson and Potter, The Four Faces of Nuclear Terrorism, 2005.

241 _{Levi, On Nuclear Terrorism, 35–49.} 242 _{“Global Fissile Materials Report 2009,” 127.}

Aside from detailing the technical/scientific aspects and hurdles a terrorist has to build a nuclear weapons, these figures are important because they do impact the optimum implementation of preventive/defensive strategies developed to stop such incidents from occurring. It also helps with the intelligence aspect of nuclear terrorism to determine real threats from false ones.