Even after a nuclear reactor is switched off, activity continues deep inside its core. Long-lived radioactive fission products keep decaying for months or even years, releasing a weak stream of particles called antineutrinos. (Anti)neutrinos are the lightest and most elusive known particles in the Universe, and they can pass through both the reactor and its surrounding shielding with little interference.
Scientists with the Double Chooz collaboration have now measured this lingering antineutrino emission for the first time. The research, recently published in Physical Review Letters, was led by Anthony Onillon and Thierry Lassere of the Max-Planck-Institut für Kernphysik (MPIK) in Heidelberg, Germany. The findings show that antineutrino detectors can gather information about nuclear reactors even while they are shut down, potentially creating new opportunities for reactor monitoring, nuclear safety, and safeguards.
Detecting Antineutrinos From a Shutdown Reactor
The measurement took place at the Chooz nuclear power plant in northern France. The Double Chooz detector sits underground about 400 meters from the facility's two reactor cores. Inside the detector are more than 30 cubic meters of liquid scintillator, a material that produces tiny flashes of light when an antineutrino interacts within it.
