September 11, 2014
FUKUSHIMA — Three and a half years after the outbreak of the crisis at the Fukushima No. 1 nuclear power plant, efforts to contain water contaminated with radioactive substances at the plant are at a crossroads.
Resolving the radioactive water issue is the first hurdle toward decommissioning the plant. However, despite the time that has passed since the beginning of the nuclear disaster, Tokyo Electric Power Co. has been unable to curb the growing volume of contaminated water.
The following is an on-site report about how work to address the contaminated water problem is being carried out at the power plant, where workers are struggling with this difficult task.
Stemming underground flow
As Yomiuri Shimbun reporters entered the Fukushima No. 1 plant on Monday morning, a series of vertical pipes could be seen inserted in the ground at intervals of about one meter, on the inland side of the No. 4 reactor building.
This was the construction site of an “ice wall” intended to freeze soil around reactor buildings Nos. 1 to 4 using coolant, circulating within 30-meter-long pipes, to block the flow of groundwater into the reactor buildings. The ice wall is planned to stretch for about 1.5 kilometers.
Out of 1,545 pipes scheduled for installation to create the ice wall, drilling work has only been completed for about 400 pipes. The government and TEPCO plan to start freezing the soil toward the end of this fiscal year, and to maintain the ice wall for seven years.
“It’s necessary to dig straight and deep into the ground without misalignment to freeze the soil for a long period of time with certainty. We’re gathering veteran drilling experts from across the nation,” said Tadafumi Asamura of Kajima Corp., a major construction company in charge of ice wall works.
Goal remains distant
On a hill overlooking the reactor buildings, about 200 meters toward the mountains from the construction site, wells that resemble metal barrels protrude from the ground. They are a part of the “groundwater bypass system” in which untainted groundwater is pumped up from 12 wells and released to the sea.
The ice wall will be completed next spring or later, but to pump up as much untainted underground water as possible before it flows into the reactor buildings, TEPCO started operating the bypass system in May.
About 300 to 400 tons of groundwater flows into the reactor buildings each day, and becomes contaminated with radioactive substances. Over the past 3½ years, TEPCO has been keeping the contaminated water in tanks, but these tanks can now be seen everywhere across the plant premises, thick like a forest, and they are steadily approaching the limits of their capacity.
Ocean still remains vulnerable
Leakage of highly contaminated water into the sea is another problem that must be dealt with immediately.
In areas around sea walls near the turbine buildings of the Nos. 1 to 4 reactors, structures destroyed by the massive tsunami remain as they were 3½ years ago. The removal of debris containing radioactive substances has been inadequate, with radiation levels still relatively high.
In coastal areas, another array of steel pipes, this time one meter in diameter, has been driven into the ground. This is the “ocean-side wall” intended to prevent contaminated water from leaking from the buildings into the port. Construction is still underway.
In addition, the government and TEPCO announced a plan in August to construct 42 “subdrain” wells near the turbine buildings and five wells near sea walls to pump up contaminated groundwater, and discharge it into the harbor of the plant after purification.
TEPCO expects leakage of radioactive strontium to be reduced to one-fourtieth of the current 4.8 becquerels a day if contaminated water is pumped out from the subdrain wells and pits after construction of the walls is completed.
However, such new measures are seen by a local fisheries cooperative association as additional burdens. Trial fishing began two years ago, with initial catches of three kinds of marine life, including octopus. This month it widened to 51 species.
“We’re getting back to a life where we can fish,” a fisheries cooperative association official said. Amid such circumstances, the new measures are a source of growing concern among local residents.
Source: Yomiuri Shimbun