U.S. researchers have found a new method that aids faster and more accurate radioactive material detection from the air.According to the University of Michigan Engineering and Paul Scherrer Institute study, the system is capable of accurately locating a radioactive source within 6.6 feet (two meters) and measuring its activity within two percentage points of its true value.The study demonstrated that, using a specialized physics-based math framework (Bayesian inference), the system could recognize both single and mixed radioactive sources during a six-second helicopter flyover equipped with airborne detectors.Microsecond detections from nearly 100 feetThe research team recently conducted the first field test of the method in Switzerland. They placed known radiological sources on the ground, including mixed sources, and later flew a military helicopter nearly 98.43 feet (30 meters) over it. The aircraft, installed with a radiation detector in the cargo bay area, detected the identity, activity, and location of the radioactive source using the Bayesian method. The detection happened despite a weak and heavily distorted signal during a single-pass flyover, the study reported.Researchers noted that these detections were achieved within seconds, unlike the conventional techniques, which take hours or days to evaluate radiological emergencies.The stark reduction in response time, from hours or days to microseconds, was made possible by recognizing the physics happening in the backdrop of events rather than enhancing the computing power of the system, highlighted the lead author of the study.”I was surprised how much efficiency we could gain by reorganizing the physics rather than simply using more computing power,” said David Breitenmoser, a postdoctoral research fellow of nuclear engineering and radiological sciences at the University of Michigan.Splitting gamma ray journeyConventionally, a radioactive material is identified by recognizing the gamma ray pattern emitted by each material, which acts as a unique fingerprint. However, the method poses problems for air detection. These rays, while making their way up to the airborne detectors, shift energy levels due to collisions with air and aircraft and generate distorted or blurry signals.The problem is worsened because, during the single flyover, the aerial detectors only pick up a small fraction of these emitted gamma rays. As a result, interpretation using these minimal signals requires a full spectrum analysis that takes longer to match the blurry signals to the simulated energy spectra for specific radioactive sources under given flight conditions.Using the new method, Breitenmoser tried to reduce the time taken by existing methods. He cut down simulation time by splitting the gamma rays’ journey into two parts: scattering in the air and scattering within the aircraft.He factored in air temperature and humidity for atmospheric scattering calculations, while using precomputed mathematical functions specific to the helicopter model used during testing to calculate the aircraft scattering part. By integrating these values, he reduced computation time, thereby improving the response time.“Once we separated transport through the atmosphere from the helicopter response, simulations that had taken hours or days could be evaluated in microseconds,” said Breitenmoser.The study further reported that to locate the radioactive source below, the Bayesian framework constantly updates its statistical confidence by quickly comparing thousands of pre-existing spectral templates with blurred aerial data.Beyond radiological emergenciesAided by the new methods, aerial detection of radioactivity could help first responders respond faster and make more informed decisions during a radiological emergency, such as a reactor meltdown or the detonation of a nuclear weapon.This vital airborne data helps emergency teams decide who needs to be evacuated, where people should take shelter, and who should receive potassium iodide pills to protect their thyroids.“What excites me most is the combination of speed and quantitative detail that could make airborne measurements substantially more useful in both emergency response and routine monitoring,” said Breitenmoser in a statement.He added the technique could be applied to routine radiological monitoring around nuclear plants, environmental assessment and cleanup, and mineral exploration.The findings were published in the journal Nature Communications.