Leaks seen under reactor 1 containment vessel

by Kazuaki Nagata

Staff Writer

Tokyo Electric Power Co. says it has found water leaks around the bottom of the containment vessel in the reactor 1 building at the Fukushima No. 1 nuclear plant, the first time leaks have been detected near or possibly in any of the three containment vessels that experienced a meltdown in March 2011.

Tepco said Wednesday it was using a camera-equipped remote-controlled boat to check conditions when it found the two leaks.

One leak came from a rupture in a sand-cushioned drain pipe installed at the bottom of the containment vessel. The pipe is not directly connected to the containment vessel and is used to drain condensation that forms on the vessel’s surface.

Another leak was confirmed just above the suppression chamber, which is a huge donut-shaped chamber connected to the containment vessel, and one of eight vent pipes.

The suppression chamber contains water and is used to reduce pressure inside the containment vessel through vent pipes.

Akira Ono, chief of the Fukushima No. 1 plant, said of the second leak that there is another pipe above the suppression chamber and the vent pipe, and it appears that the water is leaking from around that pipe.

But Ono said it is still unknown where exactly the leak is located, and that it is conceivable the water is coming from the containment vessel.

Still, “these are significant findings to help” find the precise locations of the leaks, he said.

The remote-controlled boat was in tainted water inside the torus room that contains the suppression chamber. Radiation levels inside the torus room are running between 0.9 to 1.8 sieverts per hour, dangerously high for human exposure.

The fuel cores of reactors 1, 2 and 3 suffered meltdowns at the start of the crisis, and Tepco believes they penetrated the pressure vessels, which are inside the containment vessels, and fell to the bottoms of the containment vessels, which also apparently have cracks or holes.

The melted fuel cores are being cooled by massive injections of water, but since the containment vessels have leaks, the coolant water that has been in contact with the radioactive fuel rods is leaking into the basement of the reactor buildings to increase the amount of tainted water.

As a result, finding and plugging the leaks are crucial to solving the vexing toxic water problem.