Domestic researchers have begun searching for dark matter at nuclear power plants.
A domestic joint research team led by the Institute for Basic Science (IBS) underground experimental research group announced on 6th that it will conduct the NEON experiment to directly search for light dark matter using the world's first commercial reactor.
Dark matter is known to make up about 27% of the universe's mass and energy composition. Because direct observation is impossible, existing dark matter search studies have focused on weakly interacting massive particles called WIMPs. However, due to a lack of experimental evidence for WIMPs, researchers are seeking other alternatives to find dark matter.
The NEON experiment is an innovative experiment designed to explore dark matter in the ultralight range. Existing accelerator-based experiments primarily focus on searching for heavy particles like WIMPs, and astronomical observations indirectly study the gravitational effects of dark matter, which presents limitations for directly searching for light dark matter.
The research team conducted the NEON experiment at the Hanbit Nuclear Power Plant Unit 3 in Yeonggwang, South Jeolla Province. They installed a thallium-doped sodium iodide scintillator detector approximately 23.7 meters away from a reactor with a thermal output of 2.8 gigawatts (GW). The detector has a multilayer shielding structure made of liquid scintillator, lead, and polyethylene to minimize background radiation.
The researchers collected dark matter signal data from this detector for 1 year and 4 months. They compared and analyzed operational and downtime data from the reactor. As a result, the team successfully analyzed subtle signals in the energy range of 1-10 keV (kiloelectronvolts).
High-energy photons emitted during the nuclear fission process can interact with electrons to create dark photons. There has been a theoretical proposal that these dark photons can decay into light dark matter, and this experiment has realized that process. While a similar experiment was conducted in Taiwan, this experiment achieved a sensitivity approximately 1,000 times greater, reaching a world-class level.
Lee Hyun-soo, the deputy research team leader who led the experiment, noted, "This innovative method, utilizing the reactor as a source of dark matter, has opened a new path to search for very light dark matter," adding, "This research will overcome the limitations of existing dark matter studies and serve as a groundbreaking turning point in unraveling the secrets of cosmic formation."
The research team plans to more than double the amount of signal data collected in future experiments and apply more precise analytical techniques. The deputy research team leader added, "I express infinite gratitude for the support of Hanbit Nuclear Power Plant."
References
Physical Review Letters (2025), DOI: https://doi.org/10.1103/PhysRevLett.134.021802