Photo credit: U.S. Dept. of Energy Trinity test—the first atomic bomb test, July 1945.

The possibility that terrorists might acquire and use nuclear weapons is an urgent and potentially catastrophic challenge to global security. Nuclear weapons, the most powerful weapons of mass destruction (WMD), use the energy produced by reactions within and between atomic nuclei to generate tremendous explosive force, heat, radiation, and other harmful effects.

From the late 1940s until the end of the Cold War in the early 1990s, the world lived with the constant threat of nuclear war between the United States and the Soviet Union. The end of the Cold War offered hope that the nuclear arsenals built by the United States, Russia, China, and other countries would never be used and might eventually be completely dismantled. But a new nuclear threat quickly arose. In the final years of the 20th century and in the early years of the 21st, international terrorist organizations have repeatedly demonstrated their willingness to kill large numbers of innocent civilians to achieve their objectives. They have also made efforts to gain access to WMD, including nuclear weapons, by contacting nuclear weapon scientists and casing nuclear facilities.

While the potential of these weapons to cause injury is extremely serious (indeed a large-scale biological attack could cause more fatalities or as many fatalities as a nuclear detonation), that of nuclear weapons can be far greater, with some powerful nuclear weapons able to destroy the core of a major city.

Nuclear weapons cannot be manufactured directly from the key raw material found in nature, uranium.  Natural uranium must be "enriched" before it becomes nuclear-weapons usable, an extremely complex and costly task that only nations or large-scale commercial enterprises have the resources to undertake.  Plutonium, the other nuclear-weapons-usable material, does not exist in nature and must be produced in a nuclear reactor, another complex and costly project that only nations or large-scale commercial or scientific enterprises can perform.  For this reason, a terrorist organization can acquire a nuclear explosive only (1) by obtaining an intact nuclear weapon from a national stockpile or (2) by obtaining fissile material from stocks that were produced in highly advanced industrial facilities and then making the fissile material into a nuclear explosive. The most important and effective steps for reducing the threat of nuclear terrorism are therefore to secure, consolidate, reduce, and, where possible, eliminate nuclear weapons and fissile material.  Programs to implement such measures are under way in many countries but are far from reaching their goals.

Nuclear Fission

The nuclei of some isotopes (different types of atoms of the same element) of heavy elements such as uranium and plutonium can split when they absorb a neutron. This splitting is known as nuclear fission. Nuclear fission releases a great amount of energy in the form of heat and radiation. It also expels neutrons that can be absorbed by other nuclei, which may then fission and give off more energy and neutrons, and so on. This process is known as a fission chain reaction.

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Nuclear Fission Diagram

Unlike in nuclear explosions, where the chain reaction happens at an extremely rapid and uncontrolled pace, in nuclear reactors, the fission chain reaction takes place slowly and in a controlled manner. The resulting energy can, therefore, be used in a nuclear power reactor to generate electricity or in a nuclear research reactor to create radioactive materials needed for medicine or industry.

Isotopes capable of fission are called fissionable isotopes.  The most common fissionable isotope is uranium-238 (U-238). Large quantities of U-238 exist in nature, but U-238 does not fission very easily.  For this reason, while U-238 can be used to fuel some types of nuclear reactors, it cannot be used to create a nuclear explosion.  Other fissionable isotopes, such as uranium-235 (U-235) or plutonium-239 (Pu-239), fission much more easily.  These isotopes are called fissile isotopes.  Because they fission easily, fissile isotopes are very useful for producing energy in nuclear reactors; however, they can also be used to create a nuclear explosion.  All fissile isotopes are extremely rare, and most do not exist in nature in appreciable amounts. (Natural uranium consists of 99 percent U-238 but less than 0.7 percent U-235, while Pu-239 is not found in nature.)  Highly complex industrial processes are needed to increase the concentrations of U-235 and to produce and separate Pu-239, activities that probably are beyond the capabilities of terrorist organizations.

Nuclear Fusion

Under conditions of extreme heat and pressure, the nuclei of two isotopes of hydrogen, deuterium and tritium, can merge together to form an atom of helium.  This merging is known as nuclear fusion.  Nuclear fusion produces the light and other energy released by the sun.  Methods for using nuclear fusion slowly and safely to produce energy in reactors have not yet been developed.

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Nuclear Fusion diagram

Three Types of Nuclear Weapons

Nuclear weapons are explosive devices that rapidly release the energy produced from the fission or fusion of atomic nuclei. Pound for pound, nuclear explosives are thousands of times more powerful than chemical explosives, such as TNT.  The explosive power, or "yield," of nuclear weapons is usually expressed in the quantity of TNT that would release an equivalent amount of energy, measured in thousands of tons of TNT or kilotons (kt)—and, for the most powerful weapons, in millions of tons of TNT or megatons (mt).  For example, first-generation fission bombs built by nations have had yields in the range of 10 to 20 kt.  Considerably larger yields, however, are possible from fission weapons.  The three basic types of nuclear weapons are fission, boosted fission, and thermonuclear.

Photo credit: U.S. Dept. of Energy The atomic cloud over Nagasaki.

Fission Weapons

Fission weapons rapidly assemble somewhat more than a critical mass of fissile material to create an uncontrolled fission chain reaction.  The energy of this reaction is released within a fraction of a second, resulting in a powerful explosion.  Fission weapons were once commonly called "atomic bombs," and are the only type of nuclear weapon ever used in wartime.  The United States used one fission weapon against the Japanese city of Hiroshima and a second against the city of Nagasaki at the end of World War II, in 1945.  Since then, no nuclear weapon of any type has been used in combat.

It is possible that terrorist organizations could build fission weapons if they are able to acquire enough fissile material.  Terrorists could also obtain fission weapons from states that possess these weapons in their nuclear arsenals.

Boosted Fission Weapons

A nuclear weapon that relies primarily on fission, but obtains some of its power from fusion, is known as a "boosted fission" weapon.  A boosted fission nuclear weapon contains small amounts of two isotopes of hydrogen, deuterium and tritium, that when fused together release enormous amounts of energy.  In this type of weapon, the fission chain reaction creates the heat and pressure necessary to induce the nuclei of the hydrogen isotopes to initiate a fusion reaction, creating more energy and neutrons, which cause additional fissioning of the uranium or plutonium, thereby "boosting" the effectiveness of the fission reaction.  Many of the nuclear weapons deployed by China, France, Great Britain, Russia, and the United States are boosted fission weapons.   India, Israel, and Pakistan may also possess boosted fission weapons.

Even if terrorist organizations obtained fissile material, it is very unlikely that they would be able to build boosted fission weapons because of their technical complexity, though it is possible that terrorists could obtain a boosted fission weapon from the arsenal of a state possessing such weapons.

Thermonuclear Weapons

Thermonuclear weapons use a fission reaction to initiate a fusion reaction, from which they derive most of their power.  These weapons are commonly called "hydrogen bombs," since two isotopes of hydrogen, deuterium and tritium, are used in the fusion reaction.  The destructive power of thermonuclear weapons can be much greater than that of fission weapons. The largest thermonuclear weapons formerly deployed by the Soviet Union and the United States during the Cold War had yields measured in megatons (millions of tons of TNT equivalent).  Currently, Russia and the United States deploy large numbers of thermonuclear weapons, and China, France, and the United Kingdom also possess them.  Most aircraft and missile-launched nuclear weapons currently deployed by the five major nuclear powers are thermonuclear weapons with yields from 100 to 750 kt.

Thermonuclear weapons would be beyond the manufacturing capabilities of terrorist organizations, even if they obtained fissile material.  However, one cannot exclude the possibility that terrorists might obtain an operational thermonuclear weapon, with a yield well in excess of 100 kt, from the nuclear arsenal of a state possessing thermonuclear or boosted fission weapons.

Two Types of Fission Nuclear Weapon Designs

Even after acquiring fissile material—itself a very difficult task—terrorists hoping to possess a nuclear explosive would still face a considerable challenge in constructing a workable nuclear device.

There are essentially two designs for fission weapons, the "gun-type" design and the implosion design.  Each has distinct advantages and disadvantages that are discussed in the following section.  Both designs are within the technical reach of most states, and some technically advanced terrorist groups may also have the ability to build crude or improvised versions of a gun-type nuclear explosive device. Yields would vary according to the amount of fissile material used and the sophistication of the design, which, in turn, would depend on the scientific and technical capabilities of the bomb manufacturing team assembled by the terrorist organization.  In any case, the explosive power of a nuclear weapon designed and built by terrorists would probably be measured in the tens of kilotons at most.

It is important to realize that there is a great difference between military nuclear weapons, most likely beyond the capability of terrorists to manufacture, and the crude nuclear explosives that terrorists might be able to produce.  Military weapons require precise, predictable explosive yields and very reliable delivery systems.  In contrast, terrorist nuclear bombs need only produce an uncertain yield of a few kilotons and could be delivered by vehicles as common as trucks or cargo ships.


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Hiroshima bomb diagram

The simplest and easiest type of nuclear weapon to design and manufacture is a "gun-type" fission weapon, because it does not require sophisticated explosive or electronic components.  Gun-type weapons relying on uranium must use uranium that contains a high proportion of U-235.  This category of uranium is known as highly enriched uranium (HEU), defined as uranium enriched to more than 20 percent U-235.   Most weapons use uranium enriched to more than 80 percent U-235.  Uranium enriched to 90 percent and above is considered "weapons-grade."  A gun-type weapon uses chemical explosives to "shoot" one subcritical mass of HEU into another at high speed, much as a bullet is shot from a gun. When the two masses collide, they form a supercritical mass, which produces a nuclear explosion.

Gun-type designs need more fissile material than implosion devices, but the quantity required is still quite small in absolute terms.  The exact amount of HEU depends on the level of enrichment of the uranium used in the weapon, the explosive yield desired, and the technical sophistication of the bomb design.  The greater the enrichment, the larger the proportion of U-235, and therefore the less HEU needed to ignite the explosive chain reaction.

It is impossible to achieve a large nuclear explosion by using plutonium in a gun-type device.  Nonetheless, a plutonium gun-type bomb could release as much energy as a few tons of TNT, which could conceivably cause many casualties. Moreover, this kind of bomb would release large amounts of plutonium and other radioactive materials, thereby making it a potent radiation dispersal device (RDD), or "dirty bomb."


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Nagasaki bomb diagram

An implosion-type fission weapon is more sophisticated than a gun-type design.  An implosion weapon uses a complex arrangement of explosives to rapidly compress one or more spheres of fissile material into a critical mass.  Implosion-type weapons are more difficult to design and build than gun-type weapons, because they often require advanced explosive components and sophisticated fusing systems.

The first nuclear weapon exploded, at the "Trinity" test near Alamogordo, New Mexico on July 16, 1945, was an implosion-type weapon.  The "Fat Man" bomb dropped on Nagasaki on August 9, 1945, was also an implosion weapon, with an explosive power of about 21 kt. (In contrast, the United States considered the gun-type design of the Hiroshima bomb so reliable that it did not require testing before the weapon was used.)

Implosion weapons can use either plutonium or HEU to create nuclear explosions with yields in excess of 10 kt.  Also, they typically require much less fissile material than gun-type weapons, because they use the fissile material available in the core more efficiently. A ccording to the International Atomic Energy Agency (IAEA), a first-generation implosion-type weapon would require about 25 kg (55 lbs) of HEU or 8 kg (18 lbs) of plutonium, but more sophisticated, advanced designs could require less fissile material. Other sources estimate lower thresholds of 12-15 kg of HEU and 4 kg of plutonium.  Even the first-generation Nagasaki implosion bomb used only 6 kg (13.6 lbs) of plutonium.  This means that implosion weapons can be relatively small and light in weight.  Such smaller weapons would be highly attractive targets for terrorists seeking nuclear weapons.

Could Terrorists Build Implosion-Type Weapons?

Some experts question whether a terrorist organization, even if it obtained the necessary fissile material, could construct an implosion device because of its inherent complexity.  At the very least, the task would be considerably more difficult than building a gun-type device.  For this reason, it is far more likely that a terrorist organization could succeed in constructing a nuclear explosive having a 10 kt yield from weapons-grade uranium than from plutonium.  As HEU is likely to be far more attractive to terrorists seeking fissile material than plutonium, it should be the focus of the most immediate protection efforts.

Could Terrorists Build Other Types of Nuclear Weapons?

Advanced types of nuclear weapons include boosted fission and thermonuclear weapons. Because boosted fission and thermonuclear weapons are much more difficult to design and manufacture than fission weapons, it is extremely unlikely that terrorists would be able to build them without active assistance from a nuclear-weapon state.

Effects of Nuclear Weapons

There are several ways in which the energy released by nuclear explosions cause mass destruction, including the physical destruction of buildings and infrastructure and immense numbers of human casualties.  The destructive effects of nuclear weapons include blast, heat, radiation, fallout, and electromagnetic pulse (EMP).  The scale and/or nature of these effects are unique to nuclear weapons.  Conventional explosives can cause damage through blast and heat, but at levels thousands or millions of times less severe than those caused by nuclear weapons.  Conventional explosives also do not release radiation or cause electromagnetic pulse.


Photo credit: Atomic Archive, used by permission; A wood frame house exposed to a nuclear blast at the Nevada Test Site. The thermal radiation exposure was about one-quarter of that experienced at ground zero in Hiroshima.

The major proportion (about 50 percent) of energy from a nuclear weapon exploded on or near the earth's surface or within the atmosphere is released in the form of blast and shock waves.  The pressure from a nuclear blast can cause structures to crumble and create hurricane-force winds of hundreds of miles per hour.  The blast from a nuclear bomb equivalent in yield to the weapon dropped on Hiroshima (about 13 kt) would flatten all wooden or unreinforced masonry structures within one mile (1.6 km) from the point of explosion ("ground zero"). Shock waves from a nuclear explosion occurring on or under the ground can damage or destroy buildings in a similar manner as an earthquake.

Although a nuclear weapon has never been used in an urban environment such as New York or other cities with numerous skyscrapers and densely packed modern buildings, some experts believe that a Hiroshima-sized weapon detonated at ground or near ground level in this type of environment might show modified blast effects.  That is, while a tremendous amount of damage would be expected, the blast damage in this scenario could be significantly less than what would occur from an equivalent yield weapon detonated high above a city.  (The Hiroshima bomb detonation height was set for about 2,000 feet to maximize the blast damage.)


About 35 percent of the energy of a nuclear explosion is released as heat. Immediately after a thermonuclear explosion, the temperature at the point of explosion ("ground zero") may exceed 100 million degrees Centigrade (C).  This is about 10 times the temperature of the surface of the sun.  At these temperatures, matter cannot exist in its normal solid, liquid, or gaseous state.  Instead, atoms are stripped of all their electrons and converted to ionized plasma.

Even from considerable distances, the heat from a nuclear explosion can vaporize objects and living things, ignite combustible material, and cause painful or fatal burns on people and animals.  Depending on environmental factors, such as building materials and weather conditions, at the explosion site, the heat can also create a "firestorm" of flames and air heated to over 1000C, hot enough to melt glass and many metals.  In a Hiroshima-sized explosion, this firestorm could incinerate everything within about 1.2 miles (1.9 km) from ground zero.

Prompt Radiation

About 5 percent of the energy from a nuclear explosion is released as radiation.   The radiation released immediately after the explosion in the form of neutrons, gamma rays, x-rays, and alpha and beta particles is called prompt radiation.   The prompt radiation from a Hiroshima-sized explosion would expose people within about 1.3 miles (2 km) of ground zero to a 500 rem dose of radiation, creating a 50 percent chance of death from radiation sickness, radiation burns, and other health effects within a few days or weeks.  The actual radiation exposure a person receives depends on the amount of time exposed, the distance from the radiation source, and the amount of shielding.  For instance, within a city such as New York the numerous, dense buildings might significantly reduce the amount of prompt radiation exposure.


About 10 percent of total energy appears in "fallout"—small particles of radioactive "dust" that settle back to earth over a period of minutes to weeks.   Radioactive materials pushed high into the atmosphere by the force of a nuclear explosion can travel hundreds of miles before returning (falling) to earth, causing radioactive contamination across thousands of square miles. The intensity and duration of contamination from fallout vary with the size of the nuclear weapon and how close it exploded to the ground.  Weapons detonated at or close to ground level generate the most fallout.  For two days after a Hiroshima-sized explosion at ground level, anyone within about 1.7 miles (2.75 km) of ground zero could be exposed to a 500 rem radiation dose from fallout (resulting in a 50 percent chance of death).  Without extensive decontamination, radiation within the area would not decay to safe levels for 3 to 5 years.  Although a 12 kt surface burst would not launch significant amounts of fallout into the stratosphere, low-altitude winds could carry fallout particles many miles beyond ground zero.

Electromagnetic Pulse

The radiation from a nuclear explosion also creates a powerful electromagnetic pulse, or EMP.  Radiation from a nuclear explosion ionizes air molecules, giving them an electric charge.  These ionized air molecules interact with the earth's magnetic field to cause a surge of electromagnetic energy.  The effect is very similar to the electrical surge caused by a lightning bolt, but about one hundred times faster and thousands of times stronger.

EMP from some very large nuclear detonations can cause surges of 25,000 to 50,000 volts per meter.  This surge is strong enough to destroy unprotected electronic equipment, shut down power grids and communications networks, and completely erase a computer's memory.  If a nuclear weapon explodes on or close to the ground, EMP is generated over a relatively small area.  However, according to some calculations, the EMP could be conducted by subterranean electrical transmission lines, resulting in loss of electrical power beyond the immediate zone of the most intense destruction.   Moreover, these calculations also indicate that depending on the weapon’s yield, EMP effects could radiate significantly beyond the zone of heaviest blast damage, potentially leading to loss of electrical communications equipment for emergency first responders stationed within miles of ground zero, unless this equipment was properly electrically shielded ahead of time.  A nuclear explosion at high altitudes, unlikely to be achievable by terrorists, can generate EMP over a radius of hundreds of miles.

Strategic and Tactical Nuclear Weapons

Military planners and arms control specialists in Russia, the United States, and a number of other nuclear weapon states historically have divided their arsenals into two broad categories of weapons, “strategic” and “tactical” nuclear weapons, based upon how the weapons were intended to be used.  Strategic weapons were usually more powerful and intended to be used against the homeland of the enemy, to be delivered by long-range missiles or bombers.  Tactical nuclear weapons (TNW) were to be used principally against enemy forces in the field, to be delivered by shorter-range fighter-bombers, short-range missiles, or artillery.

Formal arms control treaties between the United States and the Soviet Union, and later, Russia, controlled deployments of strategic nuclear weapons by limiting the number and type of long-range systems intended to deliver them.  Such deployments could be monitored through inspections and by means of observation satellites.  None of these treaties, however, limited the number of strategic nuclear warheads or bombs the two sides could possess or required an inventory and accounting of such warheads or bombs.  It was generally believed, however, that if such weapons were not deployed in the field, they were held in secure central storage.

The only legally binding document that addressed substrategic nuclear weapons was the 1987 Intermediate Nuclear Forces (INF) Treaty, which provided for elimination of all land-based ballistic and cruise missiles with a range between 500 and 5,500 km, although it did not address sea or air-launched nuclear weapons within that range category.  In the fall of 1991, however, U.S. President George H.W. Bush and Soviet President Mikhail Gorbachev adopted parallel unilateral declarations on tactical nuclear weapons; Gorbachev’s declaration was confirmed by Russian President Boris Yeltsin in 1992 in the name of the Russian Federation.  According to these declarations (known as Presidential Nuclear Initiatives, or PNIs), the vast majority of warheads for short-range delivery vehicles were subject to either dismantlement or storage at central storage facilities.  A limited number of air-launched weapons (gravity bombs and short-range missiles) were kept in the category of “deployed warheads.”  PNIs included also the intermediate-range weapons that were not covered by the INF Treaty.

According to official statements, the United States completed the implementation of PNIs by the end of 2003; in 2003 and 2004, Russia declared it could complete the implementation of PNIs by the end of 2004, but only with international assistance. Although there is little reason to doubt these statements, their implementation cannot be independently verified because PNIs did not provide for any transparency and verification mechanisms; neither the numbers nor the locations of these weapons have been officially released.  Unofficial estimates put the number of U.S. tactical nuclear weapons in deployed status at less than 2,000.  The estimates of the remaining Russian tactical nuclear weapons arsenal vary widely (reaching as high as 18,000), but the number is most likely around 3,000.

It is widely believed that Tactical Nuclear Weapons are a particularly attractive target for terrorists because they are generally smaller and more portable than warheads for strategic delivery vehicles and might be more vulnerable to theft.  These concerns, as well as inadequacies of the informal regime that addresses TNW, have led many nations to call for a strengthening of the existing regime by making it legally binding and verifiable, for enhancing their safety and security, and for further reductions of the number of these weapons.

The Destructive Power of Nuclear Weapons: Hiroshima and Nagasaki

It is difficult to determine exactly how many people were killed and injured by the use of nuclear weapons against Japan in August 1945.  Reliable estimates conclude that the single 13 kt fission weapon dropped on Hiroshima, a city of about 300,000 inhabitants, killed approximately 78,000 people within a few days.  By the end of 1945, it is estimated that 140,000 people had died from immediate injuries, burns, or illness due to exposure to radiation.  By 1950, about 200,000 deaths could be attributed to the atomic bombing of Hiroshima.  The atomic bomb dropped on Nagasaki killed between 40,000 and 75,000 people.

Photo credit: Masami Onuka, Hiroshima Peace Memorial Museum,

This photo was taken on August 7, 1945, one day after the atomic bombing of Hiroshima.  This man, lying on his stomach, was burned over most of his body. He was reportedly within one km of the epicenter of the explosion.

The destructive power of nuclear weapons has increased greatly since Hiroshima and Nagasaki.  The effects of even a small nuclear explosive, such as an improvised nuclear device that terrorists might be able to make from stolen HEU, would be horrific.

How Could Terrorists Acquire Nuclear Explosives?

It would be difficult for terrorists to obtain nuclear explosives, but it is not impossible.  There are two basic paths that terrorists might pursue.  The first route involves the acquisition of an intact nuclear weapon from the arsenal of an existing nuclear weapon state.  The second path entails the acquisition of fissile material and the fabrication of a crude, improvised nuclear explosive device.

Terrorists might seek to acquire nuclear weapons or nuclear materials by a number of means:

Each of these options would involve formidable challenges and serious risks for the terrorist group.  Each would also require a great deal of money and organizational and technical resources, which would be beyond the means of all but a few known terrorist organizations.  Nevertheless, because the consequences of a nuclear detonation by a terrorist group would be so catastrophic, the possibility that terrorists might acquire nuclear weapons must be given the most serious and urgent attention.

Vulnerability of Nuclear Weapons

There are over 20,000 nuclear weapons deployed throughout the world, plus an estimated 10,000 nuclear weapons which are inactive, in reserve status, or awaiting dismantlement.   Despite the enormous number, because they are perceived to have great value, nuclear weapons are relatively easy to account for, and are located at sites maintained by armed military personnel. Thus, nuclear weapons are generally thought to be more secure than fissile material.  Notwithstanding the inherent difficulty of stealing an intact nuclear weapon, concerns remain over the security of nuclear weapons in some countries.   Many experts believe the large stockpile of Russian TNW and the much smaller arsenal of Pakistan nuclear arms are at particular risk, albeit for very different reasons.

The terrorism risks posed by Russian TNW stem from their physical properties as well as the policies for their deployment and employment.  More specifically, these threats include:

Pakistan's small nuclear arsenal, perhaps numbering up to 48 weapons, poses very different security problems.  They pertain not only to political instability, but to the continuing pressure within Pakistan and the surrounding region of Islamic militant terrorist groups and the sympathy for such groups by segments of the Pakistani military, nuclear, and intelligence establishment. These concerns have been accentuated by news of the clandestine sales of Pakistani nuclear technology-including designs for nuclear weapons-by A.Q. Khan and uncertainties about the loyalty of personnel in the Pakistani nuclear command structure.

Image copyright KNS/Reuters Some fear that North Korea could sell nuclear weapons or material to terrorists.

The severe challenges to the security of nuclear weapons seen in Russia and Pakistan have not been observed to the same degree in China, France, Great Britain, or the United States.  There is little public information about the security of India's nuclear arsenal.  Although Israel also confronts major terrorist threats, most observers believe its nuclear arms are well protected. (It is Israeli policy to neither confirm nor deny that it possesses nuclear weapons, although it is widely believed that Israel has been a nuclear state for several decades.)  In the case of North Korea, it is doubtful that non-state sanctioned terrorist organizations could operate within the country.  The United States, however, has expressed concern that due to economic demands, North Korea might attempt to sell nuclear weapons to the highest bidder, much as it has previously sold ballistic missiles, as a matter of official policy.  (In February 2005, North Korea announced for the first time that it has nuclear weapons.   In October 2006, North Korea tested a nuclear device with an estimated low yield of about 500 tons.  It is widely believed that Pyongyang possesses sufficient fissile material for a small number of nuclear warheads, possibly as many as 10.)

One of the most frightening scenarios regarding nuclear weapons security involves a "failed state."  If the government of a country such as North Korea or Pakistan collapsed because of war, a coup d'etat, or other disaster, the resulting chaos might create conditions in which terrorists could more easily obtain a nuclear weapon.

Improvised Nuclear Devices

Many experts believe that the most likely way for terrorists to acquire a nuclear explosive would be to obtain HEU and use this material to make a crude nuclear bomb, known more formally as an improvised nuclear device (IND). According to the 9/11 Commission Report, a trained nuclear engineer with an amount of fissile material about the size of a grapefruit or a large orange, together with commercially available material, could build an IND that would fit in a van or SUV.  Such a bomb would level much of Lower Manhattan.

Although an IND generally is associated with the simplest design for a nuclear explosive, it could be more sophisticated if the terrorist organization had access to individuals with expertise in nuclear engineering, nuclear physics, electronics, metallurgy, chemical processing, and explosives (probably the equivalent of an advanced degree in each of these disciplines but not necessarily actual weapons design or manufacturing experience, though such experience would be helpful).  Assembling such a team would in itself be a significant challenge, and small and poorly-funded terrorist groups are not likely to have access to all these skills.  A large, well-funded organization, however, might be able to recruit individuals with the required capabilities.

A number of terrorist groups, including some affiliated with Al Qaeda, are known to recruit scientists, engineers, and other specialists with the skills needed to improvise nuclear, chemical, or biological weapons.

Image copyright: CNN Al Qaeda nuclear bomb design.

Materials Needed to Construct an IND

By far the most difficult step for terrorists seeking to build an IND would be acquiring a sufficient amount of fissile material.  In general, the lower the enrichment in U-235, the larger amount of HEU is required to make an IND.

The International Atomic Energy Agency defines the significant quantities of fissile material as 25 kg of weapons-grade (90 percent or more) HEU equivalent and 8 kg of plutonium.  These values constitute the quantity of fissile material needed to form a nuclear weapon.  Technically sophisticated nuclear weapons states are able to build nuclear weapons of this explosive power with less fissile material, employing as little as 3-4 kg of plutonium.  While terrorists would only need small amounts of fissile material for an IND, hundreds of tons of these fissile materials have been produced and are in military and civilian stockpiles around the globe.  Much of these fissile materials are inadequately secured or held in countries at risk of political instability.

Availability of Nuclear Material to Build an IND

Photo credit: IAEA Nearly 3 kilograms of stolen HEU were seized in Prague in December, 1994.

Global stockpiles of fissile material are unofficially estimated to include some 1,830 metric tons of plutonium and 1,900 metric tons of HEU--enough for hundreds of thousands of bombs. (Most of the plutonium is embedded in highly radioactive spent fuel and thus cannot be used in nuclear explosives without use of expensive and specialized methods to separate the plutonium from the spent fuel.  Worldwide, military stockpiles contain about 250 metric tons of separated plutonium, and civilian stockpiles contain more than 230 metric tons of separated plutonium.)  While the HEU and plutonium are  overwhelmingly concentrated in the five nuclear weapon states (China, France, Russia, United Kingdom, and United States) as defined by the Nuclear Non-Proliferation Treaty, more than 50 nations each possess more than five kg of weapons-usable fissile material.  Significant quantities can be found in India, Israel, and Pakistan and possibly in North Korea.   Belgium, Germany, Japan, and Switzerland possess enough plutonium for many nuclear weapons, and some 20 metric tons of HEU exist at over 130 operational and an unknown number of nonoperational nuclear research facilities in over 40 countries as widespread as Chile, Ghana, Iran, and Jamaica.

Once the exclusive property of a handful of states, nuclear materials have spread across the globe.  Starting in the 1950s, many countries bought nuclear materials and technology, often in the form of HEU-fueled research reactors, from the United States, the Soviet Union, China, and France.  Under the Atoms for Peace program, for example, beginning in 1954, the United States shared nuclear materials and technologies with other countries, so long as the recipient states agreed to inspections of the transferred technology to ensure it was not used for military purposes.

Since the 1970s, the United States and other nuclear suppliers have taken incremental steps to reduce the civilian use of HEU, including efforts to convert HEU-fueled reactors worldwide to use low-enriched uranium (LEU) fuel that cannot be used in nuclear weapons.   In addition, the United States and Russia have launched take back programs to retrieve the HEU fuel provided to these countries.  However, due to political and economic constraints, these efforts to reverse the global spread of nuclear materials may not be fast enough and sufficiently comprehensive to secure vulnerable materials from theft, diversion, and sabotage.  In the absence of global, legally-binding standards for the security of nuclear materials, it is up to each country to secure and account for its own stockpiles based on that country's discretion and resources.  Because most countries regard nuclear material security as a state secret, no one--including the International Atomic Energy Agency, the U.S. government, or other governments--has a complete picture of which facilities are most vulnerable, and, therefore, which should be targeted for international assistance that might reduce the risks.  Those seeking fissile material will look for vulnerable facilities or individuals with access to material, making the world's nuclear material security only as strong as its weakest link.

Stocks of fissile material fall into four major categories:

Each of these categories of fissile material is potentially at risk at several types of locations: where it is produced, where it is processed or fabricated into weapons or fuel, where the weapons are deployed or the fuel used, and along a vast network of transportation links connecting those sites. Even if one focuses only on the category of HEU in the civilian nuclear sector, the scope of the physical protection problem is enormous.

The Illicit Nuclear Trafficking Database of the International Atomic Energy Agency, for example, identifies fewer than two dozen incidents of fissile material trafficking since 1991.  All of these involve material likely to have originated from the former Soviet Union.  Fortunately, none of these known cases involved sufficient quantities to permit construction of an IND. However, in December 2004, the U.S. Central Intelligence Agency published the following assessment of security over Russian fissile materials: "We assess that undetected [nuclear] smuggling has occurred, and we are concerned about the total amount of material that could have been diverted or stolen in the last 13 years."  Furthermore, in February 2005 testimony to U.S. Congress, CIA Director Porter Goss indicated that "There is sufficient [Russian nuclear] material unaccounted for so that it would be possible for those with know-how to construct a nuclear weapon."  While Goss's statement does not necessarily mean the missing nuclear material has been sold or stolen, it does indicate that Russia and the world lack an accurate baseline inventory of how much fissile material exists and where it is stored.

Image Source: U.S. Dept. of Energy DOE security forces.

Even in the United States, where security over fissile materials is considered strong, increased security measures may be needed to prevent terrorists from gaining access to nuclear-weapons material.  Although the U.S. DOE has taken measures aimed at increasing security at nuclear facilities nationwide to counter terrorist threats, some weapons-usable material at nuclear weapons laboratories may still not be adequately protected.  According to some studies, a well-organized group of terrorists could breach security at U.S. nuclear labs long enough to assemble and detonate an IND.  To address this vulnerability, DOE has ordered the consolidation of weapons-usable material at a smaller number of more secure sites and has worked to improve the strategy used by security forces to protect special nuclear material.  However, an April 27, 2004, report by the General Accounting Office (GAO, now the Government Accountability Office) found that some U.S. sites with special nuclear material have been slow to implement new security measures.

The International Atomic Energy Agency, the United States, and other countries have put in place a range of measures to monitor and secure nuclear weapons usable fissile materials in the former Soviet Union and around the world.  Nuclear material for thousands of nuclear weapons has been destroyed; security for dozens of sites housing vulnerable material has been vastly improved; and thousands of nuclear weapon scientists and technicians have been given temporary civilian jobs.

By the end of fiscal year 2004, U.S.-funded security upgrades had been made at only 56 percent of the buildings housing weapons-usable nuclear material in the former Soviet Union.  More than half of the weapons-usable material in the former Soviet Union is housed in other buildings that have yet to receive even the first round of "rapid upgrades."  Beyond the former Soviet Union, security upgrades are only just beginning leaving significant stocks of nuclear material vulnerable.

Photo credit: NNSA

Security upgrades at a nuclear facility in Central Asia.

Why Would Terrorists Use Nuclear Weapons?

Photo credit: AP Al Qaeda leader Osama bin Laden.

Acquiring weapons for the defense of Muslims is a religious duty.  If I have indeed acquired these weapons, then I thank God for enabling me to do so. And if I seek to acquire these weapons, I am carrying out a duty.  It would be a sin for Muslims not to try to possess the weapons that would prevent the infidels from inflicting harm on Muslims.
Osama bin Laden

The devastating attacks of September 11, 2001 increased global concerns about mass casualty terrorism.  In a single day, terrorists demonstrated their willingness to kill thousands of innocent people, cause billions of dollars of physical and economic damage, and wreak untold psychological harm.  Similarly, the September 2004 Beslan school siege in Russia demonstrated terrorists’ willingness to target vulnerable populations, including children.

Terrorists may attempt to use chemical, biological, or radiological weapons to cause mass casualties.  The greatest danger to the public, however, emerges from the increased potential for terrorists to pursue terrorism with nuclear explosives.

Would Terrorists Use Nuclear Weapons If They Could?

Photo credit: Alabama Dept. of Homeland Security Al Qaeda fighters.

Al Qaeda's belief system seeks to justify resorting to any level of violence to attack the West, and specifically the United States, as a means toward its ultimate goal of establishing Islamic law throughout the Muslim world under al Qaeda’s guidance. This terror network has demonstrated that it is not worried about crossing the nuclear threshold and causing unprecedented levels of destruction and is unconcerned with retaliation or its followers' reactions.  If Al Qaeda can develop the capabilities required to acquire and use nuclear weapons, there is little doubt that it will resort to nuclear terrorism.

Photo Aum Shinrikyo cult leader Shoko Asahara.

Terrorists with even a moderate level of rationality recognize that using nuclear weapons would involve crossing major political and psychological thresholds and would entail enormous risks.  Nevertheless, the growing lethality of terrorist attacks in recent years also suggests a desire on the part of some groups to create a very deadly spectacle.  An attack with a nuclear weapon or IND represents the ultimate in highly visible attacks.  The grandiosity of the event could appeal to a group's leadership, and possibly to its political sympathizers as well, because it would demonstrate enormous destructive capability and heighten their own sense of power.  In addition to the sheer destructive impact of a nuclear explosion, the aura of fear surrounding nuclear weapons could give a terrorist organization significant political capital.  The mere threat of a terrorist attack would have a powerful psychological impact on the public and could force a government into negotiations with the terrorist group.

A personal preoccupation with nuclear weapons by terrorist leaders might also drive a group to pursue the nuclear option. Such was the case with Aum Shinrikyo in the late 1980s.  Although the group also experimented with chemical and biological weapons, the cult's leader, Shoko Asahara, predicted a violent end to humanity, sparked by a nuclear cataclysm.  Asahara hoped to start a nuclear war between the United States and Japan (in spite of the fact that Japan has no nuclear weapons), claiming that Aum members would survive such a catastrophe.

Technical Capabilities and Materials

Another factor influencing the decision to pursue nuclear weapons involves the group's technical capabilities.  Any group that decides to undertake a nuclear attack will need technical capabilities that go beyond experience in making and using conventional bombs.  Such a group could try to recruit necessary experts or, possibly, take some hostage and force them to work on the group's deadly project.  But if a group already had access to sympathetic nuclear scientists and technicians, it might be much more willing to consider nuclear terrorism.  The assistance that Pakistani nuclear scientists reportedly offered to Al Qaeda is an important case in point, as such assistance could provide the terrorists with the technical skills needed to construct a nuclear weapon or IND with stolen or illegally purchased nuclear materials.

Finally, ease of access to the necessary nuclear materials is likely to be a crucial factor in the decision for nuclear terrorism.  The ability of terrorist organizations to get their hands on fissile materials or even nuclear weapons could encourage them to explore how best to use these items in the pursuit of their strategic goals.  Even when terrorists intend to create a mass-casualty disaster, without access to the nuclear materials, most terrorists would likely seek non-nuclear options such as large conventional explosives.  Preventing access to nuclear materials or weapons, therefore, makes nuclear terrorism much less likely.

How Can the World Combat the Threat of Nuclear Terrorism?

lbc_cabinet.jpg (5301 bytes)   Scene from docudrama Last Best Chance. President meeting with cabinet to discuss a nuclear terrorism threat.

While it would not be easy for terrorists to gain access to nuclear weapons or the materials needed to make them, the threat is real and the potential consequences of a nuclear terror attack are devastating.  With this threat in mind, governments and international organizations are making efforts to develop a global infrastructure for preventing nuclear terrorism.  While progress has been made toward this goal, most experts agree that accelerated action is needed in a number of areas.

A comprehensive response to nuclear terror threats requires a multi-track approach that both pursues the terrorist organizations that might seek to use nuclear weapons and blocks the pathways they might use to acquire and detonate them.

Acquiring intact nuclear weapons or acquiring fissile material and constructing an improvised nuclear device (IND) are very difficult undertakings.  Moreover, only the most radical politico-religious or apocalyptic groups would be motivated to use nuclear explosives to cause mass casualties and destruction.  Maintaining global counterterrorism efforts focused on weakening and neutralizing those few terrorist organizations that might be both motivated and capable of employing nuclear weapons or INDs is thus a crucial component of any strategy for combating nuclear terrorism.

At the same time, political instruments, diplomatic incentives, and economic sanctions can also be used to persuade groups not to resort to terrorism or to discourage states from supporting terrorists.  The successful use of all these instruments requires cooperation among nations and international organizations, coordination among government agencies, and education to engage communities and individuals in a global effort to combat terrorism.

The success of such efforts, however, will always be uncertain because terrorist organizations are extremely secretive and thus difficult to target and uproot. This reinforces the importance of pursing a parallel strategy of blocking access to nuclear capabilities.

The key elements of this strategy are to protect, consolidate, reduce, and, where possible, eliminate nuclear weapons and fissile materials so as to keep them out of the hands of terrorists. This means:

enhancing the protection of nuclear weapons and fissile material wherever they exist: where they are produced, manufactured or processed, transported, and deployed or used;
• consolidating nuclear weapons and fissile materials into as few locations as possible to simplify the task of protecting them;
• reducing existing stocks of nuclear weapons and fissile materials, while halting new production; and
• eliminating existing stocks of nuclear weapons and fissile materials, wherever possible.

lbc_ovaloffice2.jpg (5378 bytes)   Scene from docudrama Last Best Chance. President and an advisor deliberating about an impending act of nuclear terrorism.

Making this program work requires a wide range of approaches, from financial and technical assistance programs, to implementing international treaties. It also requires adapting these efforts to the conditions in particular countries.

Followng is the current status and future directions of programs and initiatives designed to accomplish these objectives. Specifically:

As former Senator Sam Nunn and Senator Richard Lugar (R-IN) have observed [Ferguson and Potter, The Four Faces of Nuclear Terrorism (Center for Nonproliferation Studies, 2004)], the priority should be to secure, consolidate, and eliminate HEU, while maintaining rigorous security around plutonium.  This point was reiterated by a U.S. government official from DOE’s Global Threat Reduction Initiative who said that HEU fuel at research reactors is the “most attractive material” for theft by terrorists and is often at “the most vulnerable facilities.” HEU is “much easier for terrorists to use” than plutonium, according to the official.  While one can't entirely discount the possibility that a sophisticated and well-financed non-state actor could produce a plutonium-fueled device, the technical obstacles are substantial.

Protecting, Consolidating, Reducing, and, Where Possible, Eliminating Excess Stocks of Nuclear Weapons

Preventing terrorists from gaining access to nuclear weapons is absolutely critical in combating nuclear terrorism.  Countries that possess nuclear weapons attempt to protect them as best they can.  Nonetheless, many experts believe that more must be done to enhance the security of nuclear weapons globally by protecting, consolidating, reducing, and, where possible, eliminating excess stocks of nuclear weapons.  The goal of nuclear weapons elimination, in fact, is an integral component of the NPT. Under Article VI of the NPT, all of the nuclear-weapons states parties—China, France, Great Britain, Russia, and the United States—are obliged to "pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament."

Russian Nuclear Weapons

The process of returning Soviet nuclear weapons previously deployed outside of Russia to Russian territory began near the end of the Soviet regime, and by May 1992, all tactical nuclear weapons had been returned.  Although this process of nuclear weapons consolidation was positive from a nonproliferation perspective, some U.S. experts and policymakers were concerned that economic and political turmoil in the new Russian state might compromise the security of its nuclear weapons arsenal.

Photo credit: DTRA Submarine dismantlement under the CTR Program.

In response to those concerns, in 1991 the United States launched a major initiative—the Nunn-Lugar Cooperative Threat Reduction (CTR) Program.  Named after its legislative sponsors (Senators Sam Nunn and Richard Lugar), this innovative program provided U.S. funding and expertise to help the former Soviet Union safeguard and dismantle its enormous stockpile of nuclear, chemical, and biological weapons, related materials, and delivery systems.  As of January 2005, the program had succeeded in deactivating or destroying over 6,500 nuclear warheads.  Work also is under way to improve security at Russian storage sites, nuclear weapon assembly and disassembly facilities, and on nuclear warheads in transit.  Nevertheless, security gaps still remain, especially with respect to those more portable nuclear weapons that are forward deployed.  Also of concern are those older TNW that may lack PALs to prevent their unauthorized use.

Photo credit: DTRA U.S.-funded warhead security fencing. Photo credit: DTRA

A useful step in addressing these security concerns would be for Russia to implement fully its pledges under the 1991-92 Presidential Nuclear Initiatives regarding tactical nuclear weapons.  Ideally, all TNW that are not dismantled should be stored at exceptionally secure facilities far from populated regions.  In parallel, the United States should declare its intention to return to U.S. territory the small number of air-launched TNW currently deployed in Europe.  Although probably less at risk to terrorist seizure than tactical nuclear weapons forward deployed in Russia, there no longer is a military justification for their presence in Europe.  The U.S. action, while valuable in its own right, might be linked to Russia's agreement to move its tactical nuclear arms to more secure locations.

While the efforts of the United States and Russia to reduce and/or eliminate nuclear weapons have been met with some, albeit very limited, success, Moscow and Washington, and indeed, the world should address the threat posed by the arsenals’ hair-trigger status. Years after the end of the Cold War, Russia and the United States have been unable to overcome mutual suspicion and continue to maintain their nuclear-tipped missiles fueled, targeted, and ready for launch, raising the possibility that terrorists might seize and gain control of launch mechanisms.  Terrorists could also hack into early warning systems and/or spoof a launch, prompting a counterattack from the other side.   Moscow’s aging early warning network could be especially vulnerable to such attacks, and the U.S. system, too, is not foolproof, as evidenced by an investigation several years ago that revealed an electronic backdoor that could theoretically allow hackers to order the launch of Trident missiles.

Pakistani Nuclear Weapons

Although little definitive information is available about the operational security of Pakistan's relatively small nuclear arsenal, many analysts worry that political instability, the presence within the country of Islamic militant groups, and the uncertain loyalties of senior officials in the nuclear chain of command increase the risk that Pakistan's nuclear arms could fall into the hands of terrorists.  Political reforms that strengthen civilian institutions and reduce the opportunities for extremist elements to prosper in Pakistan would significantly reduce the potential for terrorists to gain access to nuclear weapons.  It is widely believed that Pakistan's nuclear weapons do not possess advanced security features such as PALs, and some experts have recommended that the United States provide assistance to Pakistan for the purpose of improving security over its nuclear arms.

Such assistance, however, is constrained by U.S. law and the provisions of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).  Under the NPT, no state can provide information that would facilitate the development or manufacture of nuclear weapons; thus Washington cannot provide details concerning internal PALs, which would necessarily require revelation of the inner workings of nuclear weapons.  Moreover, U.S. rules concerning restricted data would also bar the transfer of such information.   However, the United States is permitted to provide information regarding general "best practices" in securing nuclear weapons.  Although Pakistan has declared publicly that its nuclear arsenal is secure, it is apparently ready to accept U.S. support for enhancing security over its nuclear armory.  To the extent that Pakistan keeps the nuclear and non-nuclear components of its nuclear weapons separate, this would greatly complicate terrorist efforts to seize an intact nuclear weapon.

Nuclear Weapons in Other Countries

The special challenges to the security of nuclear weapons seen in Russia and Pakistan have not been observed to the same degree in China, France, Great Britain, or the United States.  For those nuclear weapon states—as well as others possessing nuclear arms—the most effective strategy for keeping the weapons out of the hands of terrorists is to enhance their security, consolidate their locations, reduce their numbers, and move toward their elimination.

There is little public information about the security of Indian or Israeli nuclear weapons.  India periodically confronts civil violence among the country’s opposing religious groups, and Israel faces constant terrorist challenges.  Assembled Indian nuclear weapons, like their counterparts in Pakistan, are not known to be equipped with advanced security features, and their nuclear and non-nuclear components are believed to be stored separately.  Although there have been no reports of the United States directly sharing information with India on nuclear weapons security, it is likely that Washington has offered to do so or will make such an overture given the July 2005 U.S.-India Cooperation Agreement.  However, the same constraints on U.S. nuclear weapons assistance to Islamabad should apply to New Delhi.  In the case of Israel, most observers believe that its nuclear arms are well-protected given the general state of Israeli security precautions.

There is no reliable information about the number of North Korean nuclear weapons or the manner in which they are secured. Although there are many things to be worried about regarding North Korean nuclear brinkmanship, the nature of the police state probably guarantees the security of the weapons as long as the state does not collapse.  The main fear is that the government might attempt to sell some component of its nuclear stockpile to another state or terrorist organization.  The Proliferation Security Initiative (PSI) is a new tool that could be used to counter such an effort, although its effectiveness in interdicting and seizing nuclear exports is open to question.  In addition, through discussions known as the Six-Party Talks, China, Japan, Russia, South Korea, and the United States hope to negotiate an agreement with North Korea to dismantle its nuclear weapons programs in return for economic assistance and security guarantees.

Protecting, Consolidating, Reducing, and, Where Possible, Eliminating Fissile Materials

The amount of fissile material around the world is enormous, and large quantities of HEU and plutonium are not adequately protected.  As long as this material exists in a form that can be readily used in nuclear weapons, the potential exists for terrorists to employ it for destructive purposes.

Significant efforts are under way to try to alleviate this global danger, and the United States and other countries have pledged billions of dollars toward this goal. These efforts include:

While much has been done to protect, consolidate, reduce, and, where possible, eliminate fissile materials, less than half of the work has been done after more than a decade.  In some cases, it will still be a decade or more before the work is completed.

Internationally Funded Programs to Secure Fissile Material in Russia

Russia possesses more than 600 tons of fissile material outside of nuclear weapons, material requiring the highest level of security.  Although all of the programs aimed at addressing the potential threats posed by these materials were initiated by the United States, many other countries are now also working with Russia on these efforts.  In 1999, the Council of Europe announced a Joint Action to provide Russia with nonproliferation assistance.  In June 2002, Canada, France, Germany, Great Britain, Italy, Japan, Russia, and the United States (the G-8 nations) announced the G-8 Global Partnership Against the Spread of Weapons and Materials of Mass Destruction.  The participants have pledged to provide $20 billion over 10 years to fund projects, initially in Russia, to prevent terrorists, or those that harbor them, from acquiring or developing nuclear, chemical, radiological or biological weapons, missiles, or related equipment and technology.  However, only a small fraction of this assistance was earmarked for nuclear material security.

The Global Partnership has not yet reached its goal of $20 billion in pledges, and of the approximately $17.5 billion in pledges received, only a portion has been allocated to projects, as of December 2006.  In addition to the G-8 countries, thirteen additional nations have joined the Global Partnership as donors, and Ukraine has joined Russia as a recipient.

Ending Civilian Commerce in HEU

gtri.jpg (21848 bytes) IAEA Director-General Mohamed ElBaradei, then-U.S. Secretary of Energy Spencer Abraham, and U.S. Ambassador Kenneth Brill at a press conference announcing GTRI in Vienna in May 2004.

The United States has led efforts to reduce the civilian use of HEU.  In 1978, it launched the Reduced Enrichment for Research and Test Reactors (RERTR) program, which seeks to develop new LEU fuel and targets to replace HEU.  In 1992, in order to encourage foreign users of U.S.-origin HEU to convert their reactors and production processes to LEU, the U.S. Congress adopted the Schumer Amendment, which restricts U.S. exports of HEU to facilities that meet a set of stringent conditions.  In mid-1995, the United States also initiated the first of a series of operations to remove Soviet-origin HEU from vulnerable sites outside of Russia.  The latest step in this campaign to reduce the civilian use of HEU was the unveiling of the Global Threat Reduction Initiative (GTRI) in May 2004.  Among its goals, the GTRI seeks to "minimize and eventually eliminate any reliance on HEU in the civilian fuel cycle, including conversion of research and test reactors worldwide from the use of HEU to the use of LEU fuel and targets."  Through GTRI, Russia, the United States, and other countries plan to accelerate their work with the International Atomic Energy Agency (IAEA) to return all eligible Soviet-origin fresh HEU to safer storage in Russia by the end of 2006, to return all eligible Soviet-origin spent fuel to Russia by the end of 2010, and to return eligible U.S.-origin research reactor spent fuel to the United States within 15 years. GTRI partners also intend to convert all eligible research reactors using HEU to operate on LEU fuel, focusing first on the most vulnerable facilities, and to identify and secure nuclear materials not covered by other cooperative programs.

Many countries that possess HEU lack the resources or the political will to provide adequate security for this nuclear material. In these cases, moving the HEU elsewhere for safekeeping or downblending it to LEU is essential to reduce the risks of nuclear terrorism.

As of the end of 2006, DOE reported 45 of 106 reactors, or 42 percent of the target group, as having been fully or partially converted to use LEU fuel.  It hopes to complete conversions on the remaining reactors that can be converted using available LEU fuels by 2014.  However, 55 research reactors, for various reasons, are not included in the DOE’s reduced enrichment program.

DOE’s Global Threat Reduction Initiative has compiled data indicating there are more than 120 research reactors or associated facilities worldwide where 20 kg or more of HEU is located.  Since U.S.-funded threat reduction efforts began in the 1990s, HEU from more than a dozen U.S.-supplied sites have been removed, as well as HEU from four locations in former Soviet republics (Georgia, Kazakhstan, Latvia, and Uzbekistan) and seven Soviet-supplied sites (Serbia, Romania, Bulgaria, Libya, the Czech Republic, Poland, and the former East Germany).  From may 2004 to December 2006, GTRI has repatriated about 496 kilograms of fresh and spent HEU fuel to Russia.

Each of the removal operations required extensive planning and several of them involved substantial bureaucratic battles among different U.S. agencies and between national governments.  Through GTRI and other programs, the United States, the IAEA, and other partners are studying ways to accelerate the process and reduce the costs of HEU removal, with the goal of returning all Soviet- and Russian-origin HEU (both fresh and spent fuel) to Russia by the end of 2010.

While the removal of Soviet-origin HEU is significant, a large amount of U.S.-origin HEU also has been repatriated to the United States.  As of September 2006, about 3,300 kg of HEU in fresh and spent fuel had been transported to the United States for final disposition. But this represents roughly half of all the HEU fuel provided to other nations by the United States.

Vulnerable HEU, wherever it is housed, is a threat to all countries.  Each nation, therefore, has a stake in seeing that nuclear weapons and materials are stored securely and properly accounted for.  In spite of this pressing need, the few binding international standards for weapons and materials security are weak, leaving security issues to the discretion of the possessor states.  In addition, there is no central information repository that tracks the security of nuclear materials worldwide and thus no means for the international community to know where security assistance is most needed.

With the April 2004 passage of UN Security Councel Resolution 1540, states are required to pass laws establishing “appropriate, effective” physical protection and accounting of nuclear and other WMD-related materials.  But the resolution, which has the potential of providing a basis for international security standards, as yet does not include specific language that defines what is meant by “appropriate, effective” and few steps have been taken to help countries improve security systems to meet their obligations.  A modest step forward in enhancing the physical protection of nuclear material was taken in July 2005 when the Convention on the Physical Protection of Nuclear Materials was amended, extending a legally-binding obligation to protect civilian nuclear materials.  However, the amendment has yet to be ratified and the language of the amendment provides only general security principles as opposed to specific security standards.