Quantum sensors reduce X-ray uncertainty by up to 8 times at US nuclear sites

Researchers in the US have accurately measured X-ray emissions from a total of three radioactive elements, including uranium, plutonium and neptunium, with ultrasensitive quantum sensors. The sensors were designed at the National Institute of Standards and Technology (NIST) in Maryland. According to the researchers, they could greatly improve how nuclear material is monitored at power plants and weapon facilities. Radioactive elements are typically identified through their distinctive gamma-ray emissions. Nevertheless, certain elements produce X-rays within the same energy range. This overlap can make it harder to determine exactly what nuclear material is present and in what quantities. For the project, the researchers measured X-rays emitted by the three radioactive elements. Their findings reduced uncertainty in X-ray energies by between one-third and one-eighth compared with earlier results. “Our measurements support international nuclear safeguards by enabling more precise accounting of material in nuclear facilities,” Jonathan Dean, PhD, a NIST physicist, said. Tiny energy changes The team used devices called transition edge sensors (TESs), originally developed at NIST. The sensors work like extremely sensitive miniature thermometers. Each of them features a superconducting film that’s cooled to a fraction of a degree above absolute zero. At this temperature, as per the researchers, the film sits at the boundary between behaving as a superconductor with no electrical resistance, and an ordinary metal with measurable resistance. When an individual particle of light, such as an X-ray photon, strikes the sensor, it imparts a minuscule amount of heat. This causes the film’s electrical resistance to rapidly increase. A transition-edge sensor can detect the number of photons hitting it. Credit: S. Kelley / NIST The change’s size corresponded to the photon’s energy, which allowed the team to make highly precise measurements. Using the sensors, the team measured X-rays from uranium, plutonium and neptunium in energy ranges that overlap with gamma-ray emissions. Meanwhile, removing this so-called X-ray background noise could make it easier to determine the ratios of different isotopes within nuclear material. Isotope ratios can indicate how radioactive material is intended to be used. As an example, uranium-235 makes up about 0.7 percent of all naturally occurring uranium. Nuclear reactor fuel requires it to be enriched to several percent, while weapons-grade uranium can contain around 90 percent. More accurate isotope measurements could strengthen nuclear material accounting and international safeguards. Faster nuclear fuel checks NIST said the technology could make operations at nuclear power plants much more efficient. Producing electricity via uranium fission involves several stages. The composition of nuclear fuel may need to be assessed before operations can move to the next step. But faster measurements could shorten these waiting periods, potentially increase efficiency and reduce costs. That said, the technology does have a limitation. TES detectors require refrigeration systems capable of keeping them extremely close to absolute zero, making handheld versions impractical. However, the detectors can operate anywhere with enough electricity to run their cooling equipment. Samples can also be transported to laboratories equipped with the sensors. “Our instruments are compatible with both approaches,” Dean concluded in a press release. NIST and Los Alamos National Laboratory have already installed TES detectors at three US Department of Energy laboratories for nuclear material monitoring. The technology is also being used at major research facilities, including CERN, SLAC National Accelerator Laboratory, Argonne National Laboratory and Brookhaven National Laboratory. The scientists are now working to improve the detectors’ accuracy and make their refrigeration systems smaller, simpler and less expensive. NIST has also began exploring their use in fundamental particle research and space science. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Based in Skopje, North Macedonia. Her work has appeared in Daily Mail, Mirror, Daily Star, Yahoo, NationalWorld, Newsweek, Press Gazette and others. She covers stories on batteries, wind energy, sustainable shipping and new discoveries. When she's not chasing the next big science story, she's traveling, exploring new cultures, or enjoying good food with even better wine.