The operator of the nuclear complex said that the plutonium is believed to have been discharged from nuclear fuel at the plant, which was damaged by the devastating March 11 earthquake and tsunami.
While noting that the concentration level does not pose a risk to human health, the utility firm said it will strengthen monitoring on the environment in and around the nuclear plant.
Meanwhile, high levels of radiation exceeding 1,000 millisieverts per hour have been detected in water in a trench outside the No. 2 reactor’s building at the nuclear plant, with the contaminated water suspected to have come from the reactor’s core, where fuel rods have partially melted, authorities said Monday.
The government’s Nuclear and Industrial Safety Agency said the electric power company, known as TEPCO, is expected to pump out similarly highly contaminated water that has been building up in the basement of the No. 2 reactor’s turbine building, which is connected to the trench, to eventually remove the water.
The company said the high radiation level in water in the trench connected to the No. 2 complex was detected Sunday, adding that the radiation level in the air in the trench stood at 100 to 300 millisieverts.