23 Septembre 2014
More than three years since it was crippled by a megaquake, tsunami and triple core meltdown, the Fukushima No. 1 power plant is still bleeding tons of toxic radioactive water into the Pacific Ocean.
Since the crisis in 2011, the water solution that saved eastern Japan from nuclear calamity has developed into a wider problem that is stoking public concern about seafood safety and what the utility will do when the plant runs out of space for its seemingly endless lines of water tanks.
To improve the situation, Tepco has been taking steps to reduce the daily buildup of tainted water and to empty the filled trenches running beneath it.
One of those steps, the so-called groundwater bypass, finally began showing progress this week. The bypass is designed to reduce the amount of groundwater merging with tainted water from the plant by pumping it up beforehand and discharging it into the sea.
Other steps have proved unsuccessful, including a recent effort to build ice walls between two of the flooded turbine buildings and their trenches.
The mingling of the waters is a huge headache for Tepco: 400 tons of groundwater seep into the cracked reactor and turbine buildings every day. It then mixes with highly radioactive water in the flooded basements of reactors 1, 2 and 3, which were hit by the meltdowns, and increases the overall volume.
To stop the buildup, Tepco started using wells to pump up the groundwater before it seeps into the buildings. It is then dumped into the sea after radiation checks.
The bypass project, launched in late May, was something Tepco had wanted to try for a long time because it looked like a promising solution.
But it took a while to convince local fishermen to let them dump the untainted water into the sea.
The utility estimated the bypass project would cut the amount of groundwater seepage by about 50 tons daily after three to four months. On Thursday, however, it said the reduction was 50 to 80 tons.
“We all believe this result is better than our previous analysis,” Tepco spokesman Shinichi Kawamura told a news conference.
Tepco is pumping up 300 to 350 tons of groundwater each day, and as of Friday had released 35,979 tons.
“If the groundwater bypass is really cutting the amount by that much, it’s good progress,” said Atsunao Marui, a groundwater expert who is a member of a government panel dealing with the tainted water issue.
But the bypass is only part of the solution, Marui said.
“The project is designed to work effectively with other measures, such as paving the ground surface of the site” and the ice walls, said Marui, who is also a researcher at the National Institute of Advanced Industrial Science and Technology, a semi-public research body.
The plan is for the underground ice walls to encircle the reactor and turbine buildings to prevent the groundwater from entering. It also plans to pave the site to halt rainwater seepage.
Once all these measures are in place, they will work together to stop the tainted water from increasing, he said.
Storage tanks at the plant are already holding close to 400,000 tons of contaminated water, so the utility is eager to slow the rate of increase.
But the groundwater bypass is important for another reason, he said, which is to determine whether groundwater from the west side of the plant is contaminated.
That is where hundreds of full storage tanks stand and where there have been several leaks. Contaminated water may have seeped into the ground and polluted the groundwater.
“It’s important to continuously monitor so groundwater can be discharged safely. . . . If some wells pump up contaminated water that can’t be dumped into the sea, the effect of the project would be smaller,” he said.
Tepco set up 12 wells to pump groundwater, and water from one well was found with a high level of tritium.
Tepco also wants to pump up water from wells dug around the reactor buildings to divert more groundwater, but the beleaguered utility will have to get consent from local fishermen because it wants to dump it into the sea. Tepco does not know when it will be able to start this project.
Although the bypass project has started showing signs of life, the utility is still trying to find a way to deal with the plant’s utility trenches, which are filled with highly contaminated water.
The trenches, which run beneath the plant, were built to house cables and pipes needed to transport electricity and water to the reactor and turbine buildings. The pipes were installed to bring in seawater for cooling purposes.
The trenches are connected to the basements and run underneath the flooded turbine buildings. The toxic water is entering the trenches via small spaces in the pipes and cables.
Leaving the tainted water in the trenches is risky.
For instance, if another major quake hits and damages the trenches, the toxic water will escape and contaminate the groundwater.
Tepco said the trenches connected to the No. 2 and No. 3 turbine buildings are filled with radioactive water but can’t be drained until the leaks from the buildings are plugged first.
To do that, Tepco started building ice walls. It has installed freezing pipes and thrown in tons of ice and dry ice over the past few months, but the utility has been unable to seal the leaks completely.
While about 90 percent of the wall is up and running, the rest of it hasn’t been able to freeze because the water is flowing too fast.
Tepco is trying to figure out how it can seal up the leaky parts by other means, such as by using fillers, but it is still unclear when it will be able to plug the leaks.
Marui said Tepco has been spending too much time trying to make the ice walls work, and should give up and explore other alternatives.