This is not a new problem in nuclear reactors, sometimes occurring if a fuel rod has a crack. It is typically handled by removing the fuel rods from the reactor and letting the xenon isotope gradually dissipate over a couple of days through radioactive decay. The other option is to keep running the reactor and vent traces of the xenon gas from the reactor into the atmosphere. “The global best practice is to shut down and change out the leaking fuel rods as soon as practical,” he said. “This normally would occur way, way, way before you approach a regulatory limit.”It appeared that the reactor had released gas in the past.

Source: International New York Times June 14, 2021 13:30 UTC