It’s hard to forget the shocking TV footage of hydrogen explosions at three reactor buildings days after the massive earthquake and tsunami struck the Fukushima No. 1 nuclear plant in March 2011, resulting in a triple core meltdown and the world’s worst nuclear crisis since Chernobyl.
That was the beginning of Tokyo Electric Power Co.’s long struggle to contain radioactive material spilling outside its damaged reactors, whose dangerous decommissioning will take decades to complete.
Five years on, Tepco has cleaned up some of the debris and decontaminated the site somewhat in an effort to improve the working conditions of the thousands of workers there.
But the reactor decommissioning is still in an early stage, delayed due in part to Tepco’s struggle to contain the tons of groundwater tainted with radioactive material on a daily basis.
It’s difficult to say how far we have come with the decommissioning. But if the mountain (peak) is 100 percent, I think we have climbed about 10 percent, Akira Ono, chief of the Fukushima No. 1 plant, said last month.
Progress has been made, albeit at a snail’s pace. About 1,500 spent and unused fuel assemblies were removed from a pool in the building housing the crippled reactor 4 in 2014 a milestone in the decommissioning process. The next big step will be for Tepco to remove spent-fuel rods from the reactor 3 building in about two years.
Improving the workplace environment will also help speed up the process.
To cater to some 7,000 people who work at Fukushima No. 1 each day, Tepco has constructed a facility where they can rest and have hot meals.
The decontamination efforts at the plant has allowed workers to switch to half-face masks from full-faced ones that are uncomfortable and harder to speak through. Now, full-faced masks are only required when working at sites, such as near reactor buildings, where radiation levels are still high.
Securing enough workers is also a challenge for Tepco. But Ono played down the concern.
The decommissioning task is a new business. There are many new things to develop for the work, so I think this is a business that has a future, said Ono.
For now, the pressing task for Tepco is to reduce the increasing amount of radioactive water groundwater flowing from the mountains into the damaged basements of the reactor buildings, resulting in contaminated water.
The basement floors of the buildings housing reactors 1, 2, 3 and 4 are flooded with radioactive water generated in the process of cooling the damaged reactors. The buildings apparently have cracks where groundwater finds its way in and mixes with the tainted water.
The issue has forced the utility to build an unprecedented underground ice wall to block groundwater going into the basements of the reactor buildings. The government-backed project, which cost ¥35 billion, involves encircling the buildings with the frozen wall by freezing the soil.
If it works, Tepco may be able to achieve its goal in stopping the leakage by 2020. The ice wall technology has been used in other construction projects, but the 1.5-km wall planned for the Fukushima plant is unprecedented.
The increase of the contaminated water has been a major issue. Even though Tepco is now pumping groundwater from the wells . . . quite a lot . . . is still going into the reactor buildings. In that sense, the ice wall could be effective, said Kiyoshi Takasaka, an adviser on nuclear issues to the Fukushima Prefectural Government.
At first, an estimated 400 tons of groundwater was being contaminated daily, but the amount has decreased to about 150 tons after Tepco started pumping out groundwater and discharged it into the sea after checking radiation levels. Because rainwater seeps into the ground and increases groundwater levels in and around the plant, Tepco has also paved many areas within the site to limit this.
But if the containment fails to go as planned, radioactive water may seep into the soil around the reactor buildings, further contaminating the environment.
To date, the tainted water has remained largely inside the reactor buildings because the water level has been lower than the groundwater level outside. Since the ice wall will block the groundwater flow into the buildings, the groundwater level within the ice wall is expected to go down. However, if it becomes lower than the tainted water level, the radioactive water will escape and mix with the underground environment.
We understand that the biggest concern is that the contaminated water might escape from the buildings. We must not let that happen, Naohiro Masuda, who heads Tepco’s decommissioning division, said during a news conference on Feb. 25.
Masuda stressed that Tepco will be closely monitoring both water levels and if the groundwater level drops, it will add water from the wells, vowing the tainted water won’t leak by any chance.
And even if it leaks, he said Tepco completed the underground sea wall right by the Pacific Ocean, so the tainted groundwater will be blocked there.
We can promise that it won’t leak to the sea, he said.
THE JAPAN TIMES, LTD.