While the company has since built a makeshift sealed cooling system, underground water is breaching basement walls at a rate of about 400 tons a day and becoming contaminated, according to Tepco’s estimate. With Japan’s rainy season approaching, contaminated water levels are likely to increase at the plant 220 kilometers (137 miles) northeast of Tokyo.
Reducing radiation levels in the water and pouring it into the sea is one of two options the utility has, said Kazuhiko Kudo, a research professor of nuclear engineering at Kyushu University. The other option is “to keep building above-ground storage tanks,” said Kudo. That’s a fight Tepco can’t win without stopping the underground water pouring into the basements, Kudo said.
On March 30, Tepco started test runs of equipment that the operator says can remove 62 kinds of radioactive substances. Still, the purification system called ALPS can’t remove tritium, a hydrogen isotope. The water processing system has also had problems and was temporarily halted last week because of incorrect operation.
Leaking PitsCurrently, about 280,000 tons of highly radioactive water is stored at the Fukushima plant, according to Tepco’s latest data. That’s enough to fill about 112 Olympic-sized swimming pools, according to Bloomberg News calculations.
To store the water, Tepco dug underground pits lined with three layers of waterproof sheet to prevent seepage into the surrounding soil, according to the utility.
The same method is used in industrial waste disposal, said Koji Kumagai, a geotechnical engineering professor at the Hachinohe Institute of Technology.
A design flaw is unlikely to have caused the leaks as the method is used around the world, Kumagai said in an phone interview. “The question is whether Tepco properly inspected equipment and carried out tests before pouring radioactive water into the pits.”