Tokyo Electric Power Co. reported a delay in the underground ice wall project at its Fukushima No. 1 nuclear power plant, citing the stalled assessment of the structure due to heavy rains from a recent typhoon.
The utility reported the delay at a review meeting with the Nuclear Regulation Authority, the government’s nuclear watchdog, on Sept. 28. TEPCO initially planned to assess the effectiveness of the ice wall by the end of this month.
According to TEPCO, the volume of groundwater pumped up in areas on the sea side of the facility was supposed to have dropped by now if the ice wall functioned properly.
But the company acknowledged this had not happened.
TEPCO had sought NRA approval to freeze a section of the ice wall facing the mountainside to enhance the effect of blocking groundwater, but it did not get the go-ahead.
“It does not make sense that the company sought approval to freeze the area facing the mountainside, just because the ice wall on the sea side did not go well,” said Toyoshi Fuketa, a commissioner of the NRA, told the meeting.
The groundwater level in the sea side portion outside the ice wall reached the surface on and off between Sept. 20 and Sept. 23 when the plant was struck by torrential rain as a result of Typhoon No. 16.
TEPCO said rainwater flowed into the sea, rather than seeping into the ground, because of the higher groundwater level.
Radioactive cesium in samples taken from the sea nearby measured a record high 95 becquerels per 1 liter.
According to the company, 0.8 percent of 5,800 or so observation spots set up on the sea side section of the ice wall showed that the soil has not been entirely frozen.
TEPCO officials believe that groundwater penetrated gaps in the ice wall before pushing up the groundwater level in the area downstream near the sea.
The frozen soil wall was built around the No. 1 through No. 4 reactor buildings. The government poured 35 billion yen ($350 million) into the project.
The objective was to block groundwater from mixing with contaminated water in the basements of the reactor and other buildings.
TEPCO started freezing soil in late March, but not all of the soil turned into ice, allowing a huge volume of groundwater to accumulate.