About 5 years in the past, Areg Danagoulian, affiliate professor within the MIT Department of Nuclear Science and Engineering (NSE), turned intrigued by a technique developed by researchers at Los Alamos National Laboratory that makes use of a neutron beam to determine unknown supplies.
“They could look into a black box containing uranium and say what kind and how much,” says Danagoulian, who directs MIT’s Laboratory of Applied Nuclear Physics (LANPh). “I was thinking about the problem of verifying nuclear material in warheads, and it just dawned on me, this amazing technology could be applied to what we’re working on.”
But there was an issue: This technique, known as neutron resonance transmission evaluation (NRTA), requires an unlimited, costly equipment, limiting its utility for the sort of on-site nuclear materials functions Danagoulian and his analysis colleagues deal with. To leapfrog this impediment, they decided to make NRTA technology moveable.
A paper describing the outcomes of this effort — a first-of-kind, cell NRTA equipment with the power to detect the fundamental composition of particular supplies — seems within the May 13 version of Physical Review Applied.
“Our fundamental goal was to enable on-site technology that could be used to identify any type of nuclear material,” says Ethan A. Klein ’15, a third-year NSE doctoral pupil, and first creator of the paper. “We were able to demonstrate that even without the large, experimental setups of the national labs, our low-cost, portable system could accurately identify a range of materials.”
Co-authors of this paper embody Danagoulian; Farheen Naqvi, a analysis scientist at LANPh; Jacob E. Bickus, a army fellow at Lincoln Laboratory; Hin Y. Lee PhD ’20; and Robert J. Goldston, professor of astrophysical sciences at Princeton University and former director of the Princeton Plasma Physics Laboratory. The National Nuclear Security Administration of the U.S. Department of Energy funded their analysis.
Follow the neutrons
NRTA rests on long-established science: When bombarded with neutrons at particular vitality ranges, the nuclei of some supplies will endure a resonant interplay with these neutrons, and obtain a transition to an excited state. “The nucleus becomes a filter, essentially absorbing neutrons of a particular energy, and letting most other neutrons pass through,” explains Danagoulian.
Scientists have developed a library of distinctive neutron resonance “fingerprints” for the isotopes of many parts, together with metallic chemical parts discovered on the greater finish of the periodic desk similar to uranium and plutonium, which determine in nuclear energy methods and nuclear weapons, and parts from the center, like silver and tungsten, which serve in industrial contexts. With information of those distinctive fingerprints, it’s doable to determine an unknown, nuclear-reactive materials.
This is a method the nationwide laboratories have mastered: With high-intensity, pulsed neutron beams and delicate detectors, researchers can set up the vitality ranges of neutrons absorbed by a cloth and those who cross via, after which map these measurements towards the library of isotopic fingerprints.
Researchers from a spread of fields have begun experimenting with this technology, together with archaeologists in search of to find out the composition of historical objects. But NRTA’s most profound influence might lie within the nuclear area. “If you want to find out how much fuel is left in your reactors, you could use NRTA to sample the enrichment level of fuel pellets,” says Naqvi, mentioning one potential utility. “Or in arms control to find out whether a warhead set for dismantling is a fake or contains real nuclear materials.”
Bringing samples of such supplies to the nationwide labs is usually not sensible, with stiff safeguards for nuclear gas and materials utilized in nuclear arms. Danagoulian’s crew got down to design and construct an equipment that might rise to the challenges of on-site NRTA.
Design and construct
Klein, who’s devoting his doctoral analysis to this venture, spent months simulating the envisioned technology: a deuterium-tritium generator beaming neutrons via a tube on the goal materials, with a detector positioned simply behind. In distinction to the apparatuses at nationwide labs, which might attain lots of of meters in size, the crew’s total setup occupied simply 3 meters, and might be moved round by one individual. There have been challenges, although.
“These neutrons are produced at high energy and we had to find a way to slow them down to produce as many neutrons as possible at the energies of interest,” he says. “Shielding was also a major issue,” provides Naqvi. The “cocktail of neutrons at different energies” dancing off partitions and tools, and the gamma rays produced by nuclear reactions, she says, creates a sort of noise that obscures detection of neutrons transmitted via and people absorbed by the goal.
The researchers jury-rigged a model of their equipment utilizing mail-order elements and “a neutron source we’ve had at MIT since 1997 that had been collecting dust on a shelf,” says Klein.
They weren’t so fortunate with timing. Just as they have been prepared to start their experiments, the pandemic shut down laboratory services at MIT. Klein needed to monitor from afar when the opposite researchers carried out preliminary checks at Princeton’s Plasma Physics Laboratory, underneath the route of Robert J. Goldston. They used tungsten because the goal materials due to its robust resonances. “We had a suboptimal setup, but I saw very faint signals, and I said, ‘There is hope,’” says Danagoulian.
After a return to MIT’s safe vault testing location and several other months of iterations to cut back background neutron noise, “we had proof of concept,” says Naqvi. “We could actually identify elements like indium, silver, and uranium, and we didn’t need big devices.”
“Our setup went from something that wasn’t very sensitive to strong signals, to something sensitive to very faint signals,” says Danagoulian. He believes the pandemic might need helped in a wierd manner, with the crew doing their homework and getting ready for months whereas itching to start experiments, after which working very intensively after they secured uncommon home windows of alternative within the lab. “Counterintuitively, it contributed to rapid progress,” he says.
The crew’s technique doesn’t but seize information on the excessive decision of the nationwide labs, which have a precision to see even smaller and fainter alerts of neutron energies. But in a number of experiments, their equipment efficiently measured neutron absorption and transmission via 4 totally different targets, matching isotopic fingerprints to deduce the composition of goal materials.
“This is powerful technology, encumbered and inhibited in the past by enormous cost and inaccessibility,” says Danagoulian. “And now we have taken away that cost and size barrier.” He estimates a price ticket of lower than $100,000 for moveable NRTA, versus lots of of tens of millions for the nationwide labs’ equal.
Glen Warren, chief of the Safeguards and Arms Control Team on the Pacific Northwest National Laboratory, finds the crew’s work “quite innovative.” On the premise of this analysis, he’s collaborating with Danagoulian on a National Nuclear Security Administration/Department of Energy-funded venture exploring the applying of NRTA in arms control. Warren says MIT’s compact equipment “may enable in-field measurements … to confirm that an object presented as a warhead contains nuclear material, which improves our confidence that the object is a warhead.”
Danagoulian’s crew is presently getting ready a paper summarizing experiments that present their technology may also detect the quantity of a component in a goal materials. This might show very important in nuclear safeguards program, the place figuring out exact portions of uranium and plutonium, assist distinguish between the actual factor and a pretend. And they proceed to refine the equipment to enhance the decision of measurements.
Real progress in nuclear arms verification and different areas of nuclear safety requires not simply technological breakthroughs, however a willingness to embrace these new approaches. To that finish, Danagoulian is working with companions within the nationwide labs, students, and coverage decision-makers. “We are communicating our results to the scientific, technical, and policy communities,” says Danagoulian. “There might be downsides and there might be opportunities. We will identify both, fix the downsides, and pursue the opportunities.”