Researchers from MIT and Lawrence Berkeley National Laboratory (LBNL) have developed a new approach to detecting and monitoring radioactive isotopes, drawing inspiration from an unlikely source: the popular computer game “Tetris.” Their findings, published in Nature Communications, could significantly improve nuclear safety and security, as well as everyday operations of nuclear reactors and the disposal of spent nuclear fuel.
The need for effective and reliable ways to detect and monitor radioactive isotopes has been underscored by recent events, such as the spread of radioactive isotopes from the Fukushima Daiichi Nuclear Power Plant in Japan in 2011 and the ongoing threat of a possible radiation release from the Zaporizhzhia nuclear complex in the Ukrainian war zone.
Typically, radiation is detected using semiconductor materials that produce an electrical response when struck by high-energy radiation, such as gamma rays. However, determining the direction of the radiation source is challenging due to the penetrating nature of radiation. Conventional detector arrays for sensing the direction of radiation sources are large, expensive, and include at least 100 pixels in a 10 by 10 array.
The team found that using as few as four pixels arranged in the tetromino shapes of the figures in the “Tetris” game can come close to matching the accuracy of the large, expensive systems. “The merit of using a small detector is in terms of engineering costs,” says Ryotaro Okabe, lead author of the work. “The smaller and simpler the detector is, the better it is in terms of applications,” adds Mingda Li, one of the researchers.
The key to making the system work is placing an insulating material, such as a lead sheet, between the pixels to increase the contrast between radiation readings coming from different directions. The team found that less symmetrical arrangements provide more useful information from a small array.
“Radiation mapping is of utmost importance to the nuclear industry, as it can help rapidly locate sources of radiation and keep everyone safe,” says co-author Benoit Forget, an MIT professor of nuclear engineering and head of the Department of Nuclear Science and Engineering.
In a single-blind field test at the Berkeley Lab with a real cesium radiation source, where the researchers at MIT did not know the ground-truth source location, a test device performed with high accuracy in finding the direction and distance to the source.
The researchers focused on gamma-ray sources in their study, but they believe the computational tools they developed to extract directional information from the limited number of pixels are much more general. “It isn’t restricted to certain wavelengths, it can also be used for neutrons, or even other forms of light, ultraviolet light,” adds Lin-Wen Hu, a senior scientist at MIT Nuclear Reactor Lab.
Nick Mann, a scientist with the Defense Systems branch at the Idaho National Laboratory, emphasizes the importance of this work, stating, “This work is critical to the U.S. response community and the ever-increasing threat of a radiological incident or accident.”
The research team’s innovative approach to radiation detection, inspired by the game “Tetris,” has the potential to revolutionize nuclear safety and security. By developing a more efficient and cost-effective way to detect and monitor radioactive isotopes, this technology could help prevent accidents, protect communities, and ensure the safe operation of nuclear facilities worldwide.
