Groundwater frustrates Fukushima cleanup

Groundwater flowing into the Fukushima No. 1 nuclear power plant is straining Tokyo Electric Power Co.'s efforts to control water levels and prevent radiation leaks at the stricken facility.

TEPCO says between 200 and 500 tons of groundwater is seeping into buildings and other structures on the site every day.

The company was supposed to have cut highly radioactive standing water at the No. 1, No. 2, No. 3 and No. 4 reactor buildings and the central waste treatment plant from 121,000 tons in late June to about 60,000 tons.

It has fallen far short of that target, with about 98,000 tons of radioactive water still in the buildings.

TEPCO says groundwater seeping through cracks in buildings and other channels accounts for most of the shortfall. One estimate is that, ignoring extra coolant water pumped in by TEPCO, about 35,000 tons of the difference is due to the flow of groundwater.

TEPCO is trying to manage a delicate balancing act between the groundwater levels outside the plant buildings and the amount of water in the buildings' basements. The groundwater flow increases if the groundwater level is significantly higher than the water inside, but allowing the internal water level to rise to that of the groundwater increases the risk of radioactive water flowing out during heavy rains.

TEPCO said it wants to maintain the radioactive water levels about 1 meter below the groundwater levels, and plans to resume pumping groundwater as part of that effort.

The company said Sept. 21 that equipment for purifying highly radioactive water at the plant only operated at 46.0 percent of its designed capacity in the week to Sept. 20, down 37.3 percentage points from the previous week, partly because a component unit was not operating for about two days.

In late June, TEPCO began operating a cyclic water injection and cooling system at the plant. It purifies and then reuses radioactive water to cool the nuclear reactors, reducing the need to pump in coolant from outside.