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April 28, 2011

Radioactive release inevitable, Pitt nuclear expert says

The release of nuclear materials — by accident or intentionally — is inevitable, engineering faculty member Larry Foulke said in a recent lecture on campus.

His April 14 talk, hosted by Pitt’s Center for National Preparedness, focused on the dangers associated with the nuclear resurgence — a topic made all the more timely by the recent accident at the Fukushima Daiichi nuclear power plant in Japan, noted center director Ken Sochats.

Foulke came to direct Pitt’s nuclear engineering program after retiring from a career with Westinghouse Energy Systems and the Bettis Atomic Power Laboratory.

“People sometimes ask me, ‘Is there going to be another nuclear accident?’ And I say, yes there is. Anything that humans make, anything that humans operate, will cause accidents,” Foulke said. What’s more, “I believe that, perhaps even before my lifetime is over, some terrorist will acquire nuclear materials and make a very crude nuclear weapon and detonate that weapon,” he said.

“I don’t know how to stop it. Perhaps a center like this can be influential in trying to influence the attitudes toward protection … of the nuclear material in the world.”

Foulke said that some 60 nations had sought the International Atomic Energy Agency’s help in building their civilian nuclear power industries before the Fukushima incident slowed the resurgence of interest. “There may not be 60 today but there are still perhaps 20 or 30 nations out there who are very interested in building a civilian nuclear power industry,” he said.

“As more countries use nuclear energy, there becomes more risk for proliferation of nuclear materials,” Foulke said.

His presentation was based on materials developed for the international science collaboration organization CRDF Global’s nuclear education consortium, which offers assistance to nations seeking to develop nuclear power.

“Their motivation is nuclear security and safeguards because the concern is that, as more people understand the technology associated with nuclear science and engineering, there’s more opportunity for people to do bad things with the technology,” Foulke said. “So we want to educate the rest of the world with a focus on nuclear security and safeguards.”

As the world’s population increases, the need for energy will grow, Foulke said, adding that he believes that energy will be the No. 1 problem in the world in the next 50 years.

Although he’s in favor of solar and wind power, nuclear power also must play a role in meeting the world’s energy needs, Foulke maintained. “I’m for solar, I’m for wind but I think it’s very naive to believe that solar and wind can do the job.”

Developing nuclear energy, however, allows more nuclear material to be put into circulation, he said. “As more and more countries develop the knowledge and the technology, there is a greater chance that the materials required to make nuclear weapons will be in existence,” he said.


“Proliferation is the business of the acquisition of either nuclear weapons, nuclear weapons capability or the materials that can be used to make nuclear weapons,” Foulke said, adding that the two major players in proliferation are nations and sub-national groups, more loosely labeled as terrorists. In his opinion, the latter represent a greater potential threat than does a rogue state.

Many factors serve to prevent proliferation. “If I have some fissile material, the intrinsic barrier, of course, is to get enough of it to do something bad with it,” Foulke said, adding that in addition to the radiation nuclear materials emit, they often have a heat load that makes them difficult to work with, or emit enough neutrons to make them difficult to use as a weapon.

“But intrinsic barriers aren’t enough to prevent proliferation of this nuclear material,” he said, adding that extrinsic barriers also play a role. Those include physical security — barriers such as “guards, gates and guns” at nuclear facilities — along with institutional barriers — material accountability and detection standards and international safeguards in the form of treaties and agreements.

Still, there are plenty of potential sources for those seeking to acquire nuclear materials: thousands of nuclear weapons; tons of highly enriched uranium and plutonium, and hundreds of research reactors, fuel site facilities and nuclear power plants, he noted.


Nuclear terrorists could acquire an intact nuclear weapon, improvise a nuclear device using stolen nuclear material, sabotage a nuclear power plant or other facility or make a radiological dispersal device, or dirty bomb, Foulke said.

While sabotage is a risk, “Nuclear power plants are among the most highly protected pieces of infrastructure,” making them a hard target, Foulke said.

Dirty bombs are more weapons of mass disruption than weapons of mass destruction, Foulke said. “If you took a dirty bomb and exploded it at the entrance to the Liberty Tubes, you shut down Pittsburgh,” he said. In such an event, “People are not going to stick around. They’re going to leave,” rather than stay and be exposed. “If anybody would die from the explosion of a dirty bomb, they’d die from the blast, not the radioactivity.”

The main threats of nuclear terrorism would be either the acquisition of a nuclear explosive device, or of the materials needed to make one, he said.

“The theft of a device in Pakistan, I think, is a real concern,” he said.

Foulke said it would be difficult, although not impossible, for terrorists to gain control of a usable nuclear weapon. “Even if you steal a nuclear weapon, though, you just can’t go off and light a match and set it off,” he said, noting that they contain safeguards that prevent unauthorized use.

Terrorists could steal fissile materials from production reactors or divert them from facilities such as power plants. But Foulke said, “The plutonium you get out of a nuclear power plant that is designed to make electricity is not very good nuclear material.” High costs and technical difficulty also are deterrents. “If you get some plutonium and try to put a weapon together in your garage — I just don’t think you could do it,” he said.

However, risks remain. “Even a crude nuclear weapon made out of reactor-grade plutonium could destroy the heart of a city. Many could die. Most would die from the blast,” he said, adding that such an attack also would have devastating effects on the world economy.

“I believe terrorists could build an improvised nuclear device if they get hold of fissile materials,” Foulke said. Although it would be technically challenging, he said, “They could put together a device that could level a U.S. city.”

The biggest challenge, he reiterated, would be in obtaining the fissile material.

What might terrorists do?

Terrorists won’t make weapons from reactor-grade plutonium, Foulke said. Instead, they would mine the raw materials then enrich them with clandestine technology.

Foulke explained that uranium 235, an isotope of natural uranium, is the only fissile material that occurs naturally. Others, such as uranium 233, plutonium 239 and plutonium 241, are human-made.

However, other materials such as thorium 232 or uranium 238 — both of which are found in the Earth’s crust — can be transmuted into fissile materials.

Foulke said that 99.3 percent of natural uranium, as it’s mined from the ground, is U238, a material not useful in a weapon, while 0.7 percent is U235, a fissile material that could be used in a nuclear reactor or a weapon.

Separating the U235 out of the natural uranium enriches it. The material is low-enriched if it contains less than 20 percent U235, but it’s known as highly enriched if it contains more than 20 percent U235.

He estimated that it would take 50 kilograms of highly enriched uranium to design a nuclear weapon, but that just 10 kilograms of weapons-grade plutonium — a mass about the size of a softball — would suffice.

In a nuclear power plant, some of the uranium that is used as fuel is converted to plutonium in the process, but the spent fuel wouldn’t make a very good weapon, he said, because plutonium 239 is transmuted from U238 early in the process, then turns into other types of plutonium that can’t be used for weapons.

“To make weapons-grade plutonium, you’ve got to stop the reactor quite frequently and take the plutonium out to process it. That’s no good for making electricity. If you’re an electricity-producing reactor, you don’t make weapons-grade plutonium, you make what we call reactor-grade plutonium with all these other isotopes. That’s what makes it hard to make a weapon from reactor-grade plutonium,” Foulke explained.

Enrichment technologies

In the early days of the nuclear era, Manhattan Project scientists quickly recognized the importance of learning to separate the U235 isotope from the U238 isotope, Foulke said. Their method of gaseous diffusion — a process in which the uranium was mixed with fluorine gas and then separated through a membrane — required huge amounts of energy and a facility that took up acres of land.

“This is not something you could do clandestinely,” he said. “But times are changing and this is what worries me.”

Today, centrifuges — each about 6 feet high and about a foot in diameter — can be used to separate out the isotope by spinning the gas. “This does not require acres and acres of land. It does not require megawatts and megawatts of energy for the process,” Foulke said, adding, “You know that Iran has been able to hide their work on this for a long time.”

Of even more concern, Foulke said, is laser enrichment, a newer process that doesn’t involve gas, but uranium ore. The ore is heated to a vapor then a laser is used to draw off the isotopes.

“Once this technology is available to the rest of the world, it’s going to be very easy to do this,” he warned. “The easy path if any nation wants to make a weapon: You mine your own uranium. You create your own enrichment facility that you can hide,” he said.

“I think the spread of enrichment technologies represents the greatest threat to the possibility of an improvised nuclear device by some terrorist or by some rogue nation who wants to use good stuff for bad purposes.”

—Kimberly K. Barlow

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