New tools for a new world order / Nuclear forensics touted as method to trace bomb materials, deterrent for rogue nations
Amid all the frightening uncertainties of the decades-long Cold War, one thing was reassuringly clear: If a nuclear bomb ever fell on America, everybody would know where it originated, and retribution would be swift and sure.
That guarantee was called "mutually assured destruction." The promise that a nuclear attack, however devastating, would trigger an equally devastating response was a critical component of Cold War deterrence.
And it worked.
"Deterrence ... as a matter of practice, was successful," said Allen Weiner, a professor at Stanford's Institute for International Studies and a State Department attorney from 1990 to 2001. "It was even successful more ambitiously -- not only was the development of nuclear arsenals on both sides sufficient to deter a nuclear attack by the adversary, but (it) was essentially successful in deterring conventional attacks."
At a time when nuclear devices are increasingly the weapons of choice for weaker nations rather than superpowers, can deterrence still work? Can it restrain emerging nuclear powers such as North Korea and Iran, or even smugglers and thieves and rogue scientists who sell plutonium to the highest bidder?
A growing number of respected nuclear scientists want more attention focused on the esoteric field of nuclear forensics as a means of keeping track of fissionable material and -- they hope -- enhance deterrence in an era of international terrorism and defiant nationalism.
"We need our government to develop an effective policy around that ... technical tool," said Charles Ferguson, a science and technology fellow at the Council on Foreign Relations. "I think people maybe could sleep more rested at night knowing we have a better capability to deal with this extreme act of terrorism."
The science of nuclear forensics is capable of revealing a great deal about the fissile material at the heart of a nuclear device, even if scientists arrive only after the explosion, said Michael May, the former director of the Lawrence Livermore National Laboratory, which was a pioneer in the science in the 1980s.
"The atoms all survive. They get transmuted, but they don't suddenly disappear," May said. "You only need micrograms, milligrams. You need very small amounts, and there's going to be kilograms of it spread around."
From those tiny samples, May said, nuclear detectives can extract a wealth of data in a few days or weeks.
Ratios of certain isotopes of plutonium can show how long the material was in a reactor, and how long since it was removed. Ratios of isotopes in uranium can suggest where the element was mined. Other clues, such as the presence of impurities like gadolinium, a rare-earth metal used in some reactors, can tell what kind of reactor was used to produce the fissile material or give hints of how the bomb was constructed.
The science has already had successes. Early nuclear forensic analysis of airborne debris collected near China in 1949 confirmed the Soviet Union's first nuclear test, just as air samples taken over North Korea this month confirmed its entry into the nuclear club.
In 1999, Bulgarian customs officials detained a man in possession of a lead container and documents suggesting the container was filled with uranium-235. Livermore scientists were able to identify the material -- sealed inside a glass tube and cushioned with wax -- as highly enriched uranium oxide originating in Eastern Europe.
But even modern forensics only takes you so far, May said.
"If you want to identify (material) uniquely, then you need some samples to compare it with," he said. "Otherwise, you're like someone with a DNA sample and no DNA bank."
That limitation has led scientists to call for an international database of nuclear material from around the world, a resource that could help them quickly and accurately identify -- to the limits of the science -- where the fissile material in a smuggler's pouch or a terrorist nuclear device originated.
"There is an important linkage between our technical capabilities and what is ultimately some sort of deterrence or, more precisely, a dissuasion policy," said Page Stoutland, radiological and nuclear countermeasures division leader for the Livermore lab's Nonproliferation, Homeland and International Security Directorate.
Some contend that the Cold War model of mutually assured destruction still has validity.
"If Iran is bound and determined to have nuclear weapons, let it," journalist Ted Koppel wrote in a recent New York Times op-ed. "But this should also be made clear to Tehran: If a dirty bomb explodes in Milwaukee ... the return address will be predetermined, and it will be somewhere in Iran."
The problem, he and other experts say, is that a future nuclear attack on America may not come in the form of easily traceable intercontinental ballistic missiles, but more likely as a jury-rigged bomb smuggled into port inside a cargo container or across the border in a backpack.
"People too easily jump to the conclusion that if a terrorist organization used a dirty bomb and/or a nuclear weapon, that we would know where it came from," he said. "The question is: Would we be able to identify that material and say, 'This came from X'?"
The answer to that is: Maybe.
Forensic identification has its limits -- the science is much better at ruling out a possible origin than in positively identifying that point of origin with 100 percent certainty, May said.
What's more, Ferguson noted, the presence of a specific country's fissile material in the hands of a terrorist group doesn't guarantee that the material was handed over intentionally -- or even knowingly.
"What if," he said, "terrorists got highly enriched uranium from reactors that were supplied by the United States?" -- perhaps reactors in the United States, or reactors sold for peaceful energy production to nations that are U.S. allies, but not so good at security.
"You can imagine a terrorist group conceivably could go around to several of these research reactors, getting bits and pieces of highly enriched uranium, and finally get enough to make a gun-type bomb," Ferguson said. "The bomb goes off, and who do we blame? ... Do we retaliate against ourselves?"
Nevertheless, Ferguson and other experts believe that even if a nuclear forensic database can't form the backbone of a modern form of mutually assured destruction, it still helps close enough nuclear proliferation gaps to make it worthwhile.
At a minimum, such a system could help in cases of nuclear smuggling, said Sagan, who served as a consultant to the office of the secretary of defense and at the Los Alamos National Laboratory. Increasing the ability to trace material to its source could encourage nuclear nations to be a little more careful about security, May said.
"The clearer it is that there is an attribution capability that is accepted internationally, the stronger the incentive for people in Pakistan, for instance -- which is a major place of worry -- or for some of the republics in Central Asia to make sure that nothing happens there that can be traced back to them," he said.
"That's one of the principal positive effects. Compared to biological and chemical agents, these (nuclear) things exist in comparatively few places -- too many, but probably a hundred or fewer instead of hundreds of thousands. The bulk of them should be under pretty thorough security -- lock and key. I mean, we have not seen any theft of gold from Fort Knox, and it should be that kind of security."
Even if the forensics can't prove that a country intentionally sold or gave fissile material to smugglers or terrorists, it still gives the United States or United Nations a powerful weapon to discourage rogue states from letting fissile material fall into the wrong hands, Weiner said.
"The most important thing is to enable us to go in and say, 'We know it's you. You no longer have plausible deniability. We're not going to nuke you, but this is now a very, very serious foreign policy issue between us,' " Weiner said. "This fundamentally changes the calculation, where we can say, 'There is proof. So stop it. Now.' "
Policymakers see the value of nuclear forensics. Both the U.S. Department of Defense and the International Atomic Energy Agency, the United Nations' nuclear watchdog, have written plans to collect forensic evidence after a nuclear event, and the Department of Homeland Security has created a domestic nuclear detection office, whose budget in fiscal year 2007 includes $17.7 million for nuclear attribution and forensics at Livermore and other research labs.
Significant obstacles remain to assembling the kind of database that experts say would be most useful. Perhaps the greatest is convincing the nuclear powers to give up information about their programs -- which most nations hold among their highest secrets.
"The question is: Does the threat of global nuclear terrorism pose such a high threat to these countries that they'd be willing to open up some of their nuclear facilities in order to reduce that threat? Because if it's just a matter of reducing the threat to the United States, that might not be enough of an incentive," Sagan said.
It might be preferable for the United Nations, not the United States, to take the lead in creating a response team and forensic database, experts said.
One possibility would be for the Security Council to follow up on its 2004 resolution calling on member states to prevent nonstate actors from obtaining weapons of mass destruction with a new or expanded resolution.
"As part of some kind of nonproliferation protocol, one could ultimately say that if you intend to possess highly enriched uranium, the international community believes that a sample should be placed in such-and-such a database to aid in forensics and attribution, should there be a loss of control of the material," Stoutland said. "Doing that kind of thing could lead to people better controlling the material; it could lead to people not having (highly enriched uranium)."
The permanent five members of the U.N. Security Council, all nuclear powers, could take the lead in providing material for the database as a form of mutual self-defense, suggested Harold Smith, professor at the Goldman School of Public Policy at UC Berkeley, who oversaw nuclear, chemical and biological defense programs during the Clinton administration.
"This is to our mutual benefit -- to at least have samples of the P-5 material if for no other reason than to show it did not come from a Russian arsenal, a U.S. arsenal, etc. At least there's the process of elimination," Smith said. "Let's at least take the small step."
Atoms of interest
In the event of a nuclear explosion, radiochemists would try to obtain tiny quantities of debris from the nuclear device on the ground near the point of impact and/or in the atmosphere. They would first separate the atoms into groups of chemically similar elements and then measure the radioactivity of each group. Three types of atoms are of particular interest in a forensic analysis:
-- Atoms of fissile material that did not undergo fission. Examining them allows scientists to identify the material used to make the device and, when compared to the number of fission fragments, to measure the efficiency or sophistication of the weapon.
-- New atoms created by fission and by other nuclear reactions within the fissile material. When scientists compare these, they can obtain considerable insight into the nuclear processes that were involved during the explosion.
-- Atoms of material near the fissioning core that were subjected to an intense bombardment of neutrons during the explosion and became radioactive as a consequence. These atoms provide insight into the components of the weapon and the energy of the neutrons that activated the components.
Source: Arms Control Today, October 2006: Who Did It? Using International Forensics to Detect and Deter Nuclear Terrorism (William Dunlop and Harold Smith)