MATERIALS ENGINEERING

Speaking at the 237th National Meeting of the American Chemical Society in Salt Lake City, Utah, Gerard Harbison, Ph.D., and colleagues described using computer simulations to analyze a variety of potential peroxide-based explosives in the same chemical class as triacetone triperoxide (TATP). That powerful, easy-to-make explosive was used by the "shoe bomber," Richard Reid, in his failed attempt to blow up a transatlantic airline flight in 2001. TATP has also been used by suicide bombers in the Palestinian Intifada.

Harbison's team became intrigued by "Internet lore," reports circulating on the Web claiming creation of another explosive — tetracetone tetraperoxide (TeATeP) — which is reputedly a more lethal relative to TATP. Initially working on detection methods of peroxide explosives for the Defense Advanced Research Projects Agency, the group instead began to investigate the structure of TeATeP to evaluate likelihood of its use as a terrorist's weapon.

"Our analysis indicates that potentially new and destructive terrorist materials, which would tax our detection capabilities, may be too unstable for a practical synthesis," said Harbison, a chemist at the University of Nebraska-Lincoln. "We consider it unlikely that any of the previous syntheses were actually successful, and the Internet myths about TeATeP are nothing more than that. So the good news is basically this is something we don't have to worry about."

The group investigated 20 molecular structures of various acetone peroxide compounds and found that all substances larger than TATP are likely too sensitive to be used as weapons. "The energies we're seeing in the analysis are extreme enough," Harbison said, adding that a review of previous TeATeP synthesis reports raised many questions. "If you look at the actual literature on people who claim to have made TeATeP, it's very ambiguous. We think probably what happened when people thought they were making TeATeP was that they were actually making TATP."

This synthesis error is common and often fatal, Harbison said. When trying to make TATP, a less stable relative, diacetone diperoxide, often is created. "The nice thing about doing this on the computer is first it's safe, and our results are so close to what's been experimentally measured that we have a great deal of confidence with what we're doing," Harbison said. "We're really at the stage where we can evaluate threats — potential molecules that might be dangerous — and we can really make some sort of judgment about whether those molecules are going to present a hazard in the future. We can test things with computers at a level of reliability that's comparable to personally doing the synthesis and evaluating material yourself."

There's a lot of research that deals with known threats, Harbison said. But his groups' research focuses on the idea that emerging threats will always exist. "Presumably you'd like to anticipate the threats before they come along. We're now pushing it a little further and discussing potential threats.

"Using computational chemistry, we can narrow down the domain of potential hazards, things that aren't going to be on the horizon. I think we now know so much more about not just what works for improvised-explosive-device detection but also what doesn't work, and we don't have to try it out (experimentally). We did five years ago."

Professor Drell, a professor emeritus at the SLAC National Accelerator Center, a senior fellow at Stanford University's Hoover Institution and an adviser on technical national security and arms-control for the US Government, has recently co-authored a report called Nuclear Weapons in 21st Century US National Security, in collaboration with the American Association for the Advancement of Science, the American Physical Society and the Center for Strategic and International Studies.

In his article for Physics World, he explains how and why there is need now, more than ever, to introduce globally ratified systems to control the spread of nuclear arms.

Professor Drell explains: "The world is teetering on the edge of a new and more perilous nuclear era, facing a growing danger that nuclear weapons – the most devastating instrument of annihilation ever invented – may fall into the hands of 'rogue states' or terrorist organizations that do not shrink from mass murder on an unprecedented scale.

His article makes two recommendations to Obama and his team. The first is to 'revisit Reykjavik' – Reykjavik hosted a summit in 1986 where former US President Ronald Reagan and then Soviet premier Mikhail Gorbachev agreed to begin reducing the size of their respected countries' nuclear arsenals. As the US and Russia still possess more than 90 per cent of the world's nuclear warheads, it is imperative that they take the lead, Drell says.

Drell's second recommendation is that the new Obama administration should adopt a process for bringing the Comprehensive Test Ban Treaty (CTBT) into effect. "The new administration should initiate a timely bipartisan, congressional review of the value of the CTBT for US security," he says.

Drell concludes: "With these two steps outlined above, President Obama has a historic opportunity to start down a practical path towards achieving his stated goal of 'eliminating all nuclear weapons.'"

In the new study, Jon Schwantes and colleagues note increased concern about the possibility of terrorists smuggling radioactive materials to make illegal nuclear weapons. As a result, scientists are stepping up efforts to identify and track the source of these radioactive materials using the advanced tools and techniques of a new field called "nuclear archaeology."

The scientists describe efforts to determine the origin of an unknown sample of plutonium (Pu) found in 2004 in a bottle at a waste burial trench at the Hanford nuclear site in Washington. Hanford is the earliest location for U.S. plutonium production for nuclear weapons and now the focus of a massive environmental cleanup effort due to high levels of radioactive waste that remain at the site.

Using multiple pairs of "parent" Pu and "daughter" uranium (U) isotopes, the researchers were able to correct for chemical fractionation that occurred as a result of repackaging in 2004 and determine the age of the sample. Using this technique, they estimated that the Pu in the sample had been separated from U and fission products in 1944, making it the oldest known sample of bomb-grade plutonium produced in a reactor. The only older known samples of Pu-239 were produced by the late Glenn Seaborg and his associates in the beginning of the 1940's when the existence of the element was first confirmed and characterized.

The study identified the Clinton reactor in Oak Ridge, Tenn., as reactor of origin for this material, by comparing reactor burnup modeling results with measurements of minor Pu isotopes. These results were also supported by a series of historical documents tracking the material's movement from Oak Ridge and the processing at Hanford. "Aside from the historical significance of this find, this work provides the public a rare glimpse at a real-world example of the science behind and power of modern-day nuclear forensics," the scientists note.

Journal reference:

1. Schwantes et al. Nuclear Archeology in a Bottle: Evidence of Pre-Trinity U.S. Weapons Activities from a Waste Burial Site. Analytical Chemistry, 2009; 81 (4): 1297 DOI: 10.1021/ac802286a