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Paula Cable-Dunlap: Assembling the nuclear mosaic

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If a nation tries to hide a clandestine nuclear operation, Paula Cable-Dunlap and her team will give their all to help find it.

Just don鈥檛 call their work 鈥渘uclear CSI鈥� 鈥� not where she can hear, at least.

鈥淚t鈥檚 never as easy as people make it seem,鈥� said Cable-Dunlap, who leads the National Security Sciences Directorate鈥檚 Collection Science and Engineering Group at Oak Ridge National Laboratory. 鈥淔orensics is such a grossly overused term for what we do. 鈥�

Cable-Dunlap and her group in the Nuclear Nonproliferation Division track the signs that can uncover illicit nuclear activity or validate a peaceful program鈥檚 compliance with international obligations.

鈥淒o I think the world is safer because of Paula? Absolutely,鈥� said Jeff Johnson, a senior ORNL program manager for nuclear nonproliferation research and development. 鈥淪he鈥檚 advanced the science of national security. She鈥檚 moved the ball forward in terms of nuclear forensics. Because of her, we can detect these kinds of threats at a much lower level than before. But much of the details of what she鈥檚 done will never see the light of day, and the world will probably never know the full scale of what she鈥檚 accomplished.鈥�

The clues to those threats, mostly invisible to the naked eye, can be found in what Cable-Dunlap and her fellow scientists call nuclear signatures.

鈥淚t鈥檚 like piecing together a mosaic,鈥� said Kate Buckley, a nonproliferation researcher who鈥檚 worked on projects with Cable-Dunlap for the past five years. 鈥淭he more signatures you can tie together, the more likely you are to get a good answer forensically.鈥�

Effluents 鈥� discharges that include tiny, microscopic particles of solids and gases 颅鈥� can point to nuclear processes. Emanations 鈥� invisible, intangible signals such as sound and radio frequency waves, electromagnetic pulses, and seismic vibrations 鈥� can offer the first clues to a nuclear operation underway. Seismic and acoustic measurements, for example, have been used in tests to pinpoint when ORNL鈥檚 switches on and off, even to estimate the reactor鈥檚 power levels. Artificial-intelligence systems keep a round-the-clock watch over a neverending stream of such measurements.

鈥淚t鈥檚 a whole different kind of data,鈥� Cable-Dunlap said. 鈥淲e have to determine if these signals are actually meaningful. Using artificial intelligence, you start to pick up patterns, about as well as or better than humans sifting through the data. We can measure a particular signal, compare it to the operational logs and use that data to train the AI on what to look for. I know that whole term 鈥榓rtificial intelligence鈥� tends to be overused, but I鈥檝e seen the power and it鈥檚 pretty amazing 鈥� and those technologies have been developed here at ORNL by people in my group.

鈥淭he signal doesn鈥檛 mean anything until you can correlate it to something we know is happening. You have to be able to prove it 鈥� and because we have the facilities here, boy, can we prove it.鈥�

Cable-Dunlap has made finding that proof a career for more than 25 years. She joined ORNL in March 2010 after 18 years at in Aiken, S.C., where she led the Nuclear Effluent Analysis Group and served as point-of-contact for various government agencies. Her work for the U.S. government and the , which seeks to prevent the spread of nuclear weapons, often calls her to destinations far and wide to perform or report on her research.

鈥淚 wouldn鈥檛 trade it for anything,鈥� Cable-Dunlap said. 鈥淚 found my life鈥檚 work when I figured out that I could combine being a scientist with protecting this nation.鈥�

None of that career lay in sight the day she walked out of a college biology class in tears. She鈥檇 grown up the daughter of a nurse, determined to pursue a career in medicine from childhood, and was two semesters away from a double degree in biology and chemistry, with med school waiting just beyond.

Then came time to knock out and cut up a living, breathing 鈥� and squirming 鈥� rat. All the scientific curiosity in the world wasn鈥檛 enough.

鈥淚 could not do it,鈥� Cable-Dunlap recalled. 鈥淚t bothered me to cut something living. I knew then if I couldn鈥檛 do it to a rat, I couldn鈥檛 do it to a human, even to help the person. My advisor came to see me and asked me what I was going to do. I said, 鈥楴ot that.鈥�

鈥淭hat changed my whole life 鈥� all because of a rat.鈥�

Her advisor found her a co-op student position at DuPont Imaging Systems, where work as a raw materials analyst and quality-assurance specialist brought out a lifelong obsession with instrumentation that鈥檚 stayed with her ever since.

鈥淚 fell in love with the ability to take a piece of equipment and characterize something so that you could fully understand it,鈥� she said. 鈥淚 became fascinated with material properties to figure out why something wasn鈥檛 working in the X-ray film or why one thing worked better than another. If you have a flaw in the film, the doctor could crack open a child鈥檚 chest unnecessarily, just because of a speck in the film.鈥�

She followed that fascination to graduate study in chemistry at Clemson University. While there, she and her advisor received funding from the to develop a method to analyze radioactive waste that had been vitrified into glass. She developed a method to study that waste by using the glass as an anode in an electrochemical reaction to produce a plasma for sampling 鈥� safer and more stable than trying to dissolve the glass in toxic acids to form a liquid that could be analyzed using conventional methods.

鈥淭hat way we avoided having to do extensive cleanup,鈥� she said. 鈥淎nd so I fell into the nuclear world.鈥�

In the early 1990s, Cable-Dunlap helped test material from Iraq for the IAEA following the Gulf War. Most of those samples were collected using methods less than ideal for the analysis of particles.

 鈥淢y goal was to get rid of the background materials, including filters, that were used for some collections,鈥� she said. 鈥淥ften the filters contained the very material you were trying to analyze. I realized then the way to capture samples is to capture what鈥檚 airborne at the time on a very pure collection media, to get a snapshot of a place in time.鈥�

So Cable-Dunlap did what came naturally: She found a better way. She developed a method built around ionization to break down gases in the air stream and collect cleaner, more reliable samples of particles. She and two colleagues patented a collection device using the method. That device, still considered a standard-setter, was later tested in the Atacama Desert, one of the world鈥檚 driest environments, in consideration for use aboard the Mars Rover.

When Cable-Dunlap arrived at ORNL in 2010, she and others helped obtain funding for a new testing complex, the Ultra-Trace Forensic Science Center, in ORNL鈥檚 former . The building, previously home to pioneering genetic experiments with mice, had sat vacant since the DOE discontinued its genetic research program in the early 2000s 鈥� until 颅Cable-Dunlap and her colleagues recognized its potential to become a world-class trace forensics center.

Inside the center鈥檚 pristine cleanrooms, free of outside particles 鈥� even human skin cells 鈥� that could skew testing, analysts today separate samples from across the globe into individual particles and search for their stories.

鈥淭hey have some of the best detection limits of any operation in the world,鈥� Cable-Dunlap said. 鈥淭hey鈥檙e able to achieve results that are unrivaled. We can work with researchers at the Center for Nanophase Materials Sciences and the and analyze samples down to single atoms.鈥�

Collecting those samples brings some of her greatest delight. She鈥檚 led or participated as a collector in more than 50 field tests over the years, gathering samples and piecing them into the mosaic.

鈥淧aula is not just the collection-science guru but the queen of collection in the field,鈥� said Jennifer Ladd-Lively, head of ORNL鈥檚 Proliferation Detection and Deterrence Section. 鈥淚t鈥檚 like watching a conductor in front of an orchestra. It might wear the rest of us out, but she鈥檒l be out there servicing the equipment, harvesting the samples, getting her hands dirty with the rest of us, and loving every minute.鈥�

Cable-Dunlap still loves the fieldwork, but as group leader she spends more time now on strategy 鈥� coordinating efforts, encouraging colleagues and looking for new ways to improve the science she鈥檚 devoted her life to pursuing as ORNL and the Nuclear Nonproliferation Division continue to expand.

鈥淏eing a woman in science, you can find challenges you wouldn鈥檛 expect,鈥� Buckley said. 鈥淧aula鈥檚 willing to share her experience as she鈥檚 gone through it. As a new person with new ideas, she鈥檚 always going to listen to you and support you if it鈥檚 at all possible, because she leads by uplifting those around her.鈥�

Ladd-Lively, the section head, looks up to Cable-Dunlap as one of her mentors 鈥� and now acts as her boss.

鈥淪ome of her best mentoring is in little stuff: the encouragement, the support, the push to go after something I didn鈥檛 necessarily think I could go for,鈥� Ladd-Lively said. 鈥淪ometimes you just need somebody to say, 鈥榊es, I鈥檝e been there and done that, too.鈥� She sees past the obstacles to the goal and finds a way.鈥�

Those brainstorming and mentoring sessions come with a cost. Cable-Dunlap routinely logs marathon days, toiling behind closed doors to keep safe a world that will never know to thank her.

鈥淲hat people don鈥檛 realize is Paula鈥檚 often here until late at night, long after everyone else has gone home,鈥� Buckley said. 鈥淪he鈥檚 known quite often to be the last person to leave. She does much of what she needs to do after-hours so she can spend normal business hours helping others, collaborating, and getting groups together. That鈥檚 part of what she enjoys, so she makes that choice: To put in the extra time to help others and to give that time whenever she can to whoever needs it.鈥�

For Cable-Dunlap, the mission鈥檚 worth every sacrifice.

鈥淥nce I figured out what I was inspired by, the rest was easy,鈥� she said. 鈥淚f I have this ability, I have to help protect this country in any way I can. And if I think of something that I or other people at this laboratory can do to help national security, I can鈥檛 turn a blind eye to it. I have to do my part.鈥�

ORNL is managed by UT-Battelle for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. DOE鈥檚 Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit . ~ Matt Lakin