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B-83 nuclear weapon
Atomic bombs utilize the energy released by the fission of uranium and plutonium to generate far more destructive power than any conventional bomb not only in the scale of the blast but also in their killing power. Not only do they create explosions, fireballs and shock waves, they also produce dangerous radiation which inflicts severe injuries on the human body.

The effects of nuclear explosions include massive explosive blast (shock wave), intense heat, electromagnetic pulse effects, intense radiation near detonation, death from trauma or significant radiation sickness from directed ionizing radiation and from fallout. At Hiroshima, people within a kilometer of the hypocenter received life-threatening doses of gamma rays, neutron rays and other of radiation. Fifty percent of the energy released by the bomb was in the form of shock waves; 35 percent was in heat rays, 10 percent in residual radiation and 5 percent in initial radiation.

The strength or nuclear bomb is measured in terms if kilotons (1,000 tons of TNT). The power of a 10 kiloton bomb is equal to 10,000 tons of TNT. To carry that much explosives you would need a cargo train with 100 cars. Nuclear weapons are extraordinarily powerful. The most powerful conventional weapon can only deliver about 1 percent fo the of the power of the atomic bombs dropped on Hiroshima and modern hydrogen are thousands of times more powerful than the bomb dropped on Hiroshima.

Book: The Making of the Atomic Bomb by Richard Rhodes (Simon & Schuster). The book won the Pulitzer Prize and the Nation Book Critics Circle Award.

Atomic Bomb Designs

Fission bomb assembly methods
Nuclear bombs are made with either plutonium or highly-enriched uranium. Around four kilograms (nine pounds) of plutonium or 15 kilograms (33 pounds) of highly-enriched uranium is necessary to make a nuclear bomb. Both materials are only available through nuclear weapons programs. Plutonium or highly-enriched uranium contain extraordinary amounts of energy: one gram of enriched uranium contains the energy potential of three tons of coal. Obtaining weapons-grade nuclear materials is one of the biggest obstacles that has to overcome in making a nuclear bomb.

The bomb dropped on Hiroshima was a gun-type uranium bomb in which critical mass was created with two-half-moon-shaped masses of uranium placed separately inside a tube that looks like a cannon barrel, with the two uranium masses combining into a sphere at the time of detonation. Implosion-technology described with plutonium bombs below can also be used to make atomic bombs with uranium.

Uranium 235 is the uranium isotope used to make uranium-type nuclear bombs. Enrichment typically begins with gas that is 0.7 percent uranium 235. If purified to levels of around 5 percent the uranium can be used for nuclear power plants. If it is enriched to 90 percent it capable of creating the chain reaction for nuclear bombs.

Getting explosive material---in the form of weapons-grade, highly enriched uranium or weapons grade plutonium---is generally considered the hardest part of building a nuclear bomb. Uranium enrichment involves feeding UF6 gas---obtained from uranium ore---into centrifuges, machines made with a cylinder of superlight material that enriches materials by spinning them at supersonic speeds or around 70,000 times per minute. When uranium is spun at high speeds a small portion of the heavier uranium 238 drops away, increasing the proportion if Uranium 235. The process is repeating using thousands of centrifuges that are connected with complex and fragile connections. Any slight imperfection can cause the whole system to break down.

Plutonium Atomic Bomb Designs

To make a warhead using plutonium, plutonium metal is shaped into a sphere, as small as a grapefruit, and is surrounded with high explosives. When it detonated the explosives compress the plutonium to cause a nuclear chain reaction and a huge explosion. Plutonium is not suitable for a gun-type bomb because it tends to undergo premature chain reactions in the tube.

A simple implosion-style nuclear devices like the one used at Nagasaki contains nuclear material placed in a special casing in the bomb. Nuclear fission is caused by conventional weapons placed around the sphere that detonate simultaneously at the time of detonation, shrinking the mass into a smaller shape, but a high enough density to set off the chain reaction.

This type of bomb works by following six steps. 1) Explosives are fired at precisely the same time creating an inward-directed spherical shock wave. 2) Subcritical masses of uranium-235 are blasted together into a much denser, small ball of supercritcal mass. 3) An igniter pellet made of beryllium/plutonium breaks open releasing a burst of neutrons into the supercritcal mass of uranium-235. 4) The fission reaction starts when a neutron strikes a uranium nucleus, splitting it in two; 5) As the nucleus divides into two smaller nuclei it releases two or three neutrons that continue the process in a chain reaction releasing massive amounts of heat and radiation. 6) Only after all the uranium has been "burned" will the bomb explode. [Source: Newsweek]

Gun-Type Fission Weapon

Because implosion type techniques require less nuclear material to create critical mass than a gun-type bomb it is more suitable for making a smaller and lighter bombs mounted on a warhead. Plutonium is made by bombarding uranium in a nuclear reactor and then separating out the uranium with baths of acid. To make one kilogram of plutonium takes a thousand tons of uranium ore.

To obtain the plutonium for a nuclear devise from the spent fuel rods at a nuclear power plant: 1) an organic solvent is added to separate uranium and plutonium from the waste water by-products; 2) the liquid uranium and plutonium are separated and processed to create uranium oxide, a powder, and plutonium metal; 3) at a foundry the plutonium medal is shaped into a sphere as small as a grapefruit. To make a warhead, high explosives are placed around the sphere. When detonated the explosives compress the plutonium to cause a nuclear reaction and massive explosion equal to many thousands of tons of TNT.

Terrorists Efforts to Acquire Nuclear Weapons

Dafna Linzer wrote in the Washington Post: “Of all the clues that Osama bin Laden is after a nuclear weapon, perhaps the most significant came in intelligence reports indicating that he received fresh approval last year from a Saudi cleric for the use of a doomsday bomb against the United States. For bin Laden, the religious ruling was a milestone in a long quest for an atomic weapon. For U.S. officials and others, it was a frightening reminder of what many consider the ultimate mass-casualty threat posed by modern terrorists. Even a small nuclear weapon detonated in a major American population center would be among history's most lethal acts of war, potentially rivaling the atomic destruction of Hiroshima and Nagasaki. [Source: Dafna Linzer, Washington Post, December 29, 2004]

Implosion nuclear weapon

“While the dangers certainly are real, there is considerable disagreement among security experts about the probabilities for "catastrophic terrorism." In the case of nuclear and biological weapons, the subjects of articles today and tomorrow, there are technical and scientific hurdles that have proved daunting, even for nations with sizable budgets and state-of-the-art facilities. Chemical weapons, which will be explored in an article Friday, would be somewhat easier to devise or obtain, but also far less likely to yield huge numbers of casualties. A radiological device would have similar limitations for terrorists. [Ibid]

Brian Michael Jenkins wrote in the Washington Post: “Shortly after the Sept. 11 attacks, a CIA source called Dragonfire reported that al-Qaeda terrorists had smuggled a nuclear weapon into New York. The source turned out to be wrong, but in the shadow of 9/11, al-Qaeda’s nuclear capabilities became an obsession. Despite North Korea’s demonstrated possession of nuclear weapons and Iran’s suspected nuclear weapons program, in 2008, then-CIA Director Michael Hayden identified al-Qaeda as the agency’s “number one nuclear concern.” Yet, while everyone agrees that al-Qaeda’s leaders have nuclear aspirations, there is zero evidence that the organization has ever had any nuclear capabilities. Fear has made al-Qaeda the world’s top terrorist nuclear power, yet it possesses not a single nuke. This is a lesson in how terrorism works. [Source: Brian Michael Jenkins, Washington Post, September 2, 2011; Jenkins is a senior adviser to the president of the Rand Corporation and is co-editor of “The Long Shadow of 9/11: America’s Response to Terrorism”]

See Al-Qaida

Obstacles to Creating Nuclear Weapons

Dafna Linzer wrote in the Washington Post: “Each type of weapon presents special challenges for the groups seeking to acquire it, but experts warn that the odds for a successful attack could rise significantly in the future as determined foes intersect with advancing technology. Despite the obvious gravity of the threat, however, counterterrorism and nuclear experts in and out of government say they consider the danger more distant than immediate. They point to enormous technical and logistical obstacles confronting would-be nuclear terrorists, and to the fact that neither al Qaeda nor any other group has come close to demonstrating the means to overcome them.So difficult are the challenges that senior officials on President Bush's national security team believe al Qaeda has shifted its attention to other efforts, at least for now.[Source: Dafna Linzer, Washington Post, December 29, 2004]

Fat Man internal components

"I would say that from the perspective of terrorism, the overwhelming bulk of the evidence we have is that their efforts are focused on biological and chemical" weapons, said John R. Bolton, undersecretary of state for arms control and international security. "Not to say there aren't any dealings with radiological materials, but the technology for bio and chem is comparatively so much easier that that's where their efforts are concentrating." [Ibid]

“It is also unclear how a terrorist group would know if its weapons development effort was on the right track. Nations with nuclear bombs conduct tests, including explosions that can be detected by scientists and governments. Bunn, who has published two studies on nuclear terrorism, said terrorists would not necessarily need to conduct such tests, but doing without them would increase chances that human error would foil plans or delay progress. [Ibid]

Reasons for Concern About Terrorists Creating Nuclear Weapons

Dafna Linzer wrote in the Washington Post: Still, the sheer magnitude of the danger posed by a nuclear weapon in terrorist hands -- and classified intelligence assessments that deem such a scenario plausible -- has spurred intelligence and military operations to combat a threat once dismissed as all but nonexistent. The effort includes billions of dollars spent on attempts to secure borders, retrain weapons scientists in other countries and lock up dangerous materials and stockpiles. [Source: Dafna Linzer, Washington Post, December 29, 2004]

"The thing to keep in mind is that while it is extremely difficult, we have highly motivated and intelligent people who would like to do it," said Daniel Benjamin, a former National Security Council staff member and senior fellow at the Center for Strategic and International Studies. Each type of weapon of mass destruction -- nuclear, biological and chemical -- presents special challenges for the groups seeking to acquire them, but also opportunities that can be exploited by people determined to unleash their awesome destructive powers. This is the first of three articles aimed at exploring those risks and challenges. [Ibid]

Little Boy internal components

“The most elaborate known effort by a terrorist group to develop a nuclear program was undertaken by the Japanese cult Aum Shinrikyo, which instead of stealing enriched uranium planned to mine and enrich the material itself. Members of Aum Shinrikyo, intent on world destruction when it began its 1993 quest for a nuclear weapon, had all the means to pull it off, on paper at least: money, expertise, a remote haven in which to work, and most important, a private uranium mine.But the group made dozens of mistakes in judgment, planning and execution. It shifted course, launching its chemical attack on the Tokyo subway in 1995. [Ibid]

"There are valuable lessons in Aum's experience, and there are false lessons," said Benjamin, co-author of "The Age of Sacred Terror." "The valuable lesson is that WMD terrorism is hard to do," he said. "But given that they didn't try what would be the most efficient way to put together a nuclear bomb, we shouldn't overrate their example as a reason why it's not going to happen." Al Qaeda has been on the run since the United States deprived it of a haven in Afghanistan, making it more difficult for the group to operate on such an ambitious scale. "At this moment, they are less capable of carrying out an operation like this because it would require so many different experts and operatives," Benjamin said. "But even a depleted group could do it if they got the right breaks." [Ibid]

Plausibility of Terrorists Stealing a Nuclear Bomb or the Materials to Build One

Dafna Linzer wrote in the Washington Post: Without sophisticated laboratories, expensive technology and years of scientific experience, al Qaeda has two primary options for getting a bomb, experts say, both of which rely on theft -- either of an existing weapon or one of its key ingredients, plutonium or highly enriched uranium.Nuclear scientists tend to believe the most plausible route for terrorists would be to build a crude device using stolen uranium from the former Soviet Union. Counterterrorism officials think bin Laden would prefer to buy a ready-made weapon stolen in Russia or Pakistan, and to obtain inside help in detonating it. [Source: Dafna Linzer, Washington Post, December 29, 2004]

In November 2004, Michael Scheuer, who ran the CIA's bin Laden unit, first disclosed in an interview on CBS's "60 Minutes" that bin Laden's nuclear efforts had been blessed by the Saudi cleric in May 2003, a statement other sources later corroborated. As early as 1998, bin Laden had publicly labeled acquisition of nuclear or chemical weapons a "religious duty," and U.S. officials had reports around that time that al Qaeda leaders were discussing attacks they likened to the one on Hiroshima.A week after his CBS appearance, Scheuer said at breakfast with reporters in Washington that he believed al Qaeda would probably seek to buy a nuclear device from Russian gangsters, rather than build its own. [Ibid]

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B-61 nuclear bomb

“There were as many as a dozen types of nuclear weapons in the hands of the Soviet Union at the end of the Cold War, but Russian officials have said that several kinds have since been destroyed and that the country has secured the remainder of its arsenal. The nature and scope of nuclear caches are among the most tightly held national security secrets in Russia and Pakistan. It is unclear how quickly either country could detect a theft, but experts said it would be very difficult for terrorists to figure out on their own how to work a Russian or Pakistani bomb. [Ibid]

“Newer Russian weapons, for example, are equipped with heat- and time-sensitive locking systems, known as permissive action links, that experts say would be extremely difficult to defeat without help from insiders. "You'd have to run it through a specific sequence of events, including changes in temperature, pressure and environmental conditions before the weapon would allow itself to be armed, for the fuses to fall into place and then for it to allow itself to be fired," said Charles D. Ferguson, science and technology fellow at the Council on Foreign Relations. "You don't get it off the shelf, enter a code and have it go off."The strategy would require help from facility guards, employees with knowledge of the security and arming features of the weapons, not to mention access to a launching system. [Ibid]

“Older Russian nuclear weapons have simpler protection mechanisms and could be easier to obtain on the black market. But nuclear experts said even the simplest device has some security features that would have to be defeated before it could be used. "There is a whole generation of weapons designed for artillery shells, manufactured in the 1950s, that aren't going to have sophisticated locking devices," said Laura Holgate, who ran nonproliferation programs at the Pentagon and the Energy Department from 1995 to 2001. "But it is a tougher task to take a weapon created by a country, even the 1950s version, a tougher job for a group of even highly qualified Chechen terrorists to make it go boom." [Ibid]

“Transporting a weapon out of Russia would provide another formidable obstacle for terrorists. Most of the ready-made bombs that could be stolen would be those made with plutonium, which emits far higher levels of radiation and is therefore more easily detected by passive sensors at ports than is highly enriched uranium, or HEU."I wouldn't rule out plutonium altogether, but if one were a terrorist bent upon demonstrating a nuclear explosion, the HEU route is technically much easier," said William C. Potter, director of the Center for Nonproliferation Studies at the Monterey Institute of International Studies in California. [Ibid]

Plausibility of Terrorists Building a Nuclear Bomb and Buying Nuclear Material

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Dafna Linzer wrote in the Washington Post: Such difficulties have led some nuclear experts to believe bin Laden would be more likely to try to build an improvised nuclear weapon using a combination of uranium and conventional explosives. That design, known as a gun-type device, was used in the atomic bomb over Hiroshima. While the technology is relatively simple and has been described in dozens of published scientific studies and policy journals, the path to development is filled with technological and logistical challenges -- the most significant of which is obtaining at least 50 kilograms of bomb-grade uranium. That amount would yield a slightly smaller device than "Little Boy," the code name for the Hiroshima bomb, but would be enough to obliterate any life or structure within a half-mile radius of the blast zone. "If they got less material than that, it would be really dicey that they could build such a bomb," said Ferguson, at the Council on Foreign Relations. [Source: Dafna Linzer, Washington Post, December 29, 2004]

“According to a database maintained by the United Nations' International Atomic Energy Agency, there have been 10 known incidents of HEU theft in the past 10 years, each involving a few grams or less. Added up, the stolen goods total less than eight kilograms and could not be easily combined because of varying levels of enrichment. Most important, the thieves -- none of whom was connected to al Qaeda -- had no buyers lined up, and nearly all were caught while trying to peddle their acquisitions. [Ibid]

"Making the connection between buyer and seller has proved to be one of the most substantial hurdles for terrorists," said Matthew Bunn, a senior researcher at Harvard University's Project on Managing the Atom. Of the few known attempts by al Qaeda to obtain HEU, each allegedly stumbled because there was either no seller or the material on offer was fake. "Each time they tried, they got scammed," said Bruce Hoffman, a counterterrorism expert at the Rand Corporation who has tracked al Qaeda for years.A September 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." 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." [Ibid]

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highly enriched uranium
The largest stocks outside the United States are in Russia and around the former Soviet Union, some in facilities with notoriously weak security and safety procedures."Once you have the fissile material, it's a matter of basic chemistry, basic machinery and a truck," said Holgate, now a vice president at the nonprofit Nuclear Threat Initiative. "You have to have some technical capability, but once you have those skills, it's certainly within the grasp of the kind of sophisticated, planning-capable terror organizations out there." [Ibid]

The uranium would have to be smuggled out of the facility and then transferred, possibly across several borders, seaports and airports, to a location where the device could be assembled. As described in unclassified literature, the gun-type bomb works when one mass of uranium is shot into another inside a tube. Such a device would be small enough to hide in a corner of a shipping container, but that would mean getting it to a port, onto a container and probably bribing a shipper or cargo crew to transport it.

An oil shipment would be optimal for a ready-made device, according to the congressional report, because the "size of the supertanker and thickness of the steel, especially with the use of double hulls," renders some detection equipment unusable. But HEU emits low levels of radioactivity anyway, and that could be masked with lead shielding. A primitive device could be assembled in a small garage using machine tools readily available at an auto shop and concealed in a lead-plated delivery truck about the size of a delivery van, experts said.

Dirty Bombs

Moscow dirty bomb
made with cessium
A radiological or “dirty bomb” is a bomb that uses conventional explosives to disperse radioactive material---such as plutonium, Uranium-238 from spent fuel rods from a nuclear power plant, cesium-137 or strontium-90---over a wide area. The aim of such a device is to kill and injure through exposing people to high levels of radioactivity.

As far as anyone knows a dirty bomb has never been detonated. If one was set off in a city it would have an explosive powerful enough to spread the radioactive material over several city block, with the radiation spreading out much farther than that. A sophisticated device could spread radioactivity even further. Most damaging would be a dirty bomb made with stolen plutonium or highly enriched uranium delivered with a truck bombs

A “dirty” bomb can be made with radioactive material obtained from industrial or medical sources. Relatively easy materials to obtain that could be used in a dirty bomb include Americium 241 (used in oil drilling), Cesium 137 (used in food radiation and industrial radiography), Iridium 192 (industrial uses and medical therapy) and strontium 90 (industrial heating devices).

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Jose Padilla, a Brooklyn-born U.S. citizen of Puerto Rican origin, was arrested on suspicion of plotting a "dirty bomb" attack inside the US. He was arrested at Chicago's O'Hare airport in May 2002 after stepping off a flight from Pakistan. He Padilla was held as an "enemy combatant" for three years and was convicted of plotting to kill people overseas and of supporting terrorism in 2007. [Source: BBC, August 2007]

Prosecutors told the court Padilla had traveled to Afghanistan in 1998 to train with the al-Qaeda terror network and that his fingerprints had been found on what they called an al-Qaeda application form. In 2001, officials said, he made contact with Abu Zubaydah, a senior al-Qaeda commander who is in American custody and apparently co-operating with the FBI. The US authorities alleged that al-Qaeda asked Padilla to go to Lahore in Pakistan, where he learnt how to make a dirty bomb and allegedly met several other al-Qaeda members. Coded language helped the FBI crack the case against Padilla. According to prosecutors, Padilla and two co-defendants were bugged for years by the FBI, which eventually concluded that their frequent mentions of "eggplant" and "zucchini" were really references to weaponry and ammunition.

Damage from a Dirty Bomb

The most serious casualties from a dirty bomb would be to those killed or injured by the initial blast. The radiation would be more of nuisance than a killer. It would cause panic and require months and billions of dollars to clean up. A device with between 1,000 and 10,000 curies (a radioactivity measurement) could contaminate an area the size of the Mall in Washington and take years to clean up. Buildings, even skyscrapers, might have to be torn down.

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Plutonium ring
One analyst described a dirty bomb as primarily an “economic weapon.” A computer simulation of the explosion of a devise made with two ounces of cesium-137, with 3,500 curries, in Manhattan projected that particles would spread over an area of 60 square blocks. Clean up and relocation would take years and cost tens of billions of dollars. Death and injuries would be caused mostly from he blast itself.

A Pentagon study released in January 2004, said a well-executed “dirty bomb” attack could be more dangerous than perviously thought---possibly exposing hundreds of people to lethal amounts of radiation. By some estimates the costs of the clean up from such a devise set off in the middle of New York or Washington could be higher than September 11th. People who inhaled or ingest radioactive particles could suffer from serious internal bleeding and injuries. The severity depends on the amount taken in, the type of radiation and the treatment. Some say so many people could become sick that the health care system could be seriously taxed.

Prussian blue, an artist’s pigment used for centuries, can be taken to protect people from a dirty bomb that releases elements such as cesium-137. The pigment binds with radioactive particles and expels them from the body. The U.S. government has urged drug companies to make drugs with the pigment as a precaution against a dirty bomb attack.

Image Sources: Wikimedia Commons

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.

Last updated July 2012

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