Unconventional Nuclear Weapons

This is part of IEEE Spectrum's special report: Nuclear Power Gets a Second Look

Of the countless scenarios of terrorist mayhem, none quickens the pulse quite like the menace of a nuclear bomb, and for good reason. A nuclear weapon embodies essentially everything a terrorist could hope for: the ability to kill at least tens of thousands of people at once, a fiery explosion that reverberates globally in images of death and destruction, and a lingering, lethal legacy, in the form of radioactive fallout.

Fortunately, most terrorist groups are transient, geographically dispersed, and limited in their technical resources, all factors that hardly conduce to building a nuclear bomb. Admittedly, there are shortcuts, such as buying the bomb-grade materials or even an entire weapon on the black market. But those options are somewhat less accessible than they were in the immediate aftermath of the Soviet Union's collapse, before the United States and other countries spent hundreds of millions of dollars shoring up Russia's loose and antiquated system of nuclear safeguards.

In fact, in light of last September's low-tech but catastrophic attacks, building a nuclear bomb suddenly seems an unnecessarily difficult and risky proposition. Why build a bomb when there are far cheaper and simpler ways of waging nuclear terror? Analysts have accordingly turned their attention to two other possibilities that, for all their comparative simplicity, would deliver much of the bang of a bomb. Flying a fully fueled jumbo jet into a nuclear reactor is one. The other is using radioactive nuclear materials to kill or sicken people or render tracts of land uninhabitable by, for example, scattering the materials with a conventional explosion.

Nuclear reactors are surrounded by a massive containment structure with concrete-and-steel walls more than a meter thick. These containments were designed to withstand earthquakes and extremely violent impacts, but not the sort a plunging jumbo jet would cause if fully loaded with fuel, according to the International Atomic Energy Agency (IAEA), in Vienna, Austria. In a 26 September release, the agency suggested that such an impact would not trigger a runaway nuclear reaction, because automatic safety systems would flood the reactor with water. A direct hit by a large, fueled aircraft might nevertheless breach the containment and damage the reactor, possibly causing a leak of radioactive steam and fallout.

Tens of thousands of deaths?

"An attack that would succeed in releasing a plume of radioactive materials, particularly over a nearby city, would dwarf the consequences of the World Trade Center and the Pentagon attacks," said Paul Leventhal, director of the Nuclear Control Institute, the self-described "international atomic safety watchdog" based in Washington, D.C. At a press conference there on 25 September, the institute presented the results of its analysis of such a release of radioactivity: tens of thousands of cancer deaths downwind of the plant.

The IAEA's assessment is much less grisly. It predicts that the worst damage would be confined within 10 km of the plant, and that a Chernobyl-scale disaster is extremely unlikely, given the advantages of modern reactor design and safety systems, which are designed to prevent reactions from spiraling out of control. Even so, dangerous levels of radioactivity would likely persist for 10 to 15 years.

Sharp disagreement with the Nuclear Control Institute's assessment came from Steve Kerekes, director of media relations for the Nuclear Energy Institute, the Washington, D.C.-based trade organization. "We would challenge the wild speculation about tens of thousands of deaths even if the containment were to be penetrated," he said in an interview. "The U.N. Scientific Committee on the Effect of Atomic Radiation assessed the public health effects of Chernobyl, finding 30 immediate deaths and 1800 cases of thyroid cancer. While that is tragic and inexcusable, thyroid cancer is one of the most treatable. Even that incident did not cause thousands of deaths."

Meanwhile, the Nuclear Control Institute and the Committee to Bridge the Gap, another watchdog group, have provided the U.S. Nuclear Regulatory Commission, the governmental agency that oversees nuclear licensing and safety in the United States, with a list of proposals to protect nuclear plants from terrorist attacks. These include employing troops to deter attacks from land and water, deployment of advanced anti-aircraft weapons that could deflect or destroy a full-size jetliner, and new background checks of all employees and contractors.

In a brief response to the proposals, commission chairman Richard A. Meserve stated it was "evaluating current requirements and statutory authority relating to acts or threats of terrorism, including but not limited to those that you presented in your letter."

The poor man's nuke

Radiological dispersion devices--"the poor man's nuclear weapon"--are another possibility likely to attract increasing interest from terrorists. Scattering radiation without a nuclear explosion, they are "a near-term terrorist threat," according to Michael Vatis, the founding director of the National Infrastructure Protection Center at the U.S. Federal Bureau of Investigation.

So far, terrorists and criminals have used nuclear materials on at least two occasions. In 1995, Russian-organized crime figures hid radioactive material in the office of a businessman, who eventually died from radiation sickness. In November of that same year, Chechen guerillas buried a 15-kg container of cesium, used in equipment for cancer radiation therapy, near the entrance of Izmailovo Park, a huge and popular recreation area in eastern Moscow. The container emitted a level of radiation about 200 000 times higher than the background level, but apparently did not harm any passers-by.

Osama bin Laden, the terrorist mastermind believed to be behind the attacks on the World Trade Center and the Pentagon last 11 September, reportedly made repeated and wide-ranging attempts to buy nuclear materials and even entire weapons in the 1990s. And several nations--including a few believed to be sponsors of terrorism--have dabbled in dispersion devices. In the 1980s, Iraq produced and tested conventional bombs filled with radioactive materials--apparently, spent fuel from its research reactors, according to a 1991 report by the U.S. Central Intelligence Agency. Iraq did not use the bombs against its foe at the time, Iran, possibly because of technical shortcomings in the devices.

Spent fuel is the obvious choice for the radioactive material in a terrorist device. Many tens of thousands of tons of it lie scattered around the world, including small accumulations in Iraq, Iran, Algeria, Libya, Syria, Pakistan and North Korea. A single, half-ton spent-fuel assembly from a reactor contains more than enough radioactivity to put a transportation terminal or some other strategic location out of action for months, or years, if the radioactivity is well dispersed.

Even so, terrorists would find it difficult to steal and utilize such an assembly. Ordinarily, it would be cooled and shielded in a special pool. Outside of that pool, it would instantly deliver a lethal dose of radiation to anyone who got near it.

Thus, in a more likely terrorist scenario, a state sponsor of terrorism would simply give the antagonists the spent fuel or perhaps even an entire dispersion device. Alternatively, terrorists might attack a truck or train carrying a cask loaded with as many as 32 spent-fuel assemblies. These casks are the emerging standard technology for storing and transporting nuclear waste [see "Canned Heat"]. In Germany and some other countries, loaded casks are brought to central storage facilities. In the United States and elsewhere, such transportation could begin some time in the next decade, if repositories for the waste are built as planned.

The casks are strong but not utterly impervious. They could be blown open with an antitank or similar weapon or with other shaped explosive charges, according to various analyses, such as one commissioned by the state of Nevada. The state opposes the construction of a proposed repository within its boundaries.

The job of licensing the casks falls to the Nuclear Regulatory Commission. Over the last 20 years, according to M. Wayne Hodges, deputy director of the commission's spent fuel project office, some casks were tested and analyzed at Sandia National Laboratory and at other sites for their ability to withstand damage from sabotage and other causes. He declined to provide any details, though, citing security restrictions. He did say that the commission plans new analyses in the wake of the 11 September attacks.

Some experts say more intensive studies are long overdue. "My opinion is that the NRC wasn't sufficiently conservative when they looked at these issues," said Edwin S. Lyman, the Nuclear Control Institute's scientific director. In Lyman's view, the commission concentrated optimistically on circumstantial factors that might limit the damage, "instead of thinking from the terrorist's perspective of maximizing the destruction."