First Detection of Antineutrino Afterglow from Shutdown Nuclear Reactor

Nuclear reactors may go dark, but their fuel continues to emit a faint antineutrino glow long after shutdown. In a first‑ever observation, scientists detected this residual signal, finding it closely matched predictions of radioactive decay inside the reactor core and in nearby spent‑fuel pools. The measurement confirms that antineutrinos persist as the reactor’s fuel undergoes decay, even when the reactor is offline. This breakthrough suggests that antineutrino detectors could eventually provide a non‑intrusive way to monitor reactors when they are not operating, offering a new tool for nuclear safeguards and safety oversight.