The operator of the crippled Fukushima Daiichi nuclear power plant said Monday that highly radioactive water found on the floor of the No. 3 reactor building could be a sign that water is leaking from the reactor's primary containment vessel.
Tokyo Electric Power Co. said the water could be leaking from an area where pipes are connected to the primary containment vessel.
TEPCO confirmed on Saturday that water was pouring into a drain on the first floor of the building housing the No. 3 reactor, which suffered a meltdown in the early stage of the 2011 nuclear crisis.
In a water sample taken by a remote-controlled robot, 700,000 becquerels per liter of cesium-134 and 1.7 million becquerels per liter of cesium-137 were detected.
The high radiation levels indicate it is water that has been used to cool the melted fuel inside the No. 3 reactor, according to TEPCO.
The utility is injecting water into the Nos. 1 to 3 reactors to keep the fuel inside cool, but radioactive water is accumulating at the bottom of the reactors' primary containment vessels and the basement of the reactor buildings.
To remove the melted fuel as part of the planned decommissioning process, TEPCO wants to first plug the leaks of the containment vessels and fill them with water. But TEPCO has not been able to nail down the exact locations where leaks are occurring.