Following this weeks’ contaminated water leak from a damaged tank, information occurred that water seeping from a massive underground reservoir might soon enter the ocean.
The enormous underground reservoir beneath the reactor and turbine building area was damaged during the 2011 earthquake and has been spilling highly contaminated water ever since.
According to experts familiar with the technical situation at the site, the contaminated water might soon reach the ocean. If the information is true, the recent 300-tonne water leak from a faulty over-ground tank might become rather insignificant compared with the vast quantities of water seeping from the underground reservoir on a daily basis.
The turbine buildings at the Fukushima Dai-ichi plant are about 150 metres from the ocean. According to a Japan Atomic Energy Agency document, the contaminated underground water is spreading toward the sea at a rate of about four metres a month.
At that rate, "the water from that area is just about to reach the coast", if it has not already done so, said Atsunao Marui, an underground water expert at the National Institute of Advanced Industrial Science and Technology and member of a government committee studying the contaminated water problem. "We must contain the problem as quickly as possible."
Until last month, Tepco has been reluctant to accept any contaminated water might have been leaking into the ocean, despite claims of the scientific community that caesium levels in bottom-dwelling fish have been suspiciously high ever since the accident.
Later, Tepco gave an explanation that the radioactive water might be seeping from the network of maintenance tunnels near the coast rather than from below the reactor area.
After the plant’s reactors have been damaged during the 2011 earthquake, Tepco has built an improvised system of pipes and hoses to channel water into the broken reactors.
About 1,000 tons of underground water flows into the area of the complex daily, of which 400 tons seep into the reactor and turbine basements and get contaminated. The rest is believed to come into contact with tainted water in the coastal trenches before reaching the ocean. Some of the radioactive water is treated and stored in the aboveground tanks that have been reported to leak.
On Friday, Japan’s nuclear regulator said Tepco hasn't’t put enough effort into monitoring the radioactive water storing tanks.
Speaking after a visit to the crippled facility, Toyoshi Fuketa, the Nuclear Regulation Authority Commissioner, said Tepco didn’t keep proper records about the tanks' inspections.
"Fundamentally, for a facility holding that kind of radioactive water, they did not take action that foresaw the risks of possible leaks," Fuketa said. "On top of that, and this is an impression I had before my visit, I can't help but say that the inspections were careless."
Tepco has proposed several preventive mechanism to keep the water away from the ocean - apart from chemical barriers in the ground, Tepco is in the process of building an offshore steel wall to seal off the groundwater.
The company is also considering constructing frozen walls resembling downward facing comb-shaped sticks that would enable refrigerating soil around the reactor buildings. However, the technology is unproven and will take at least until 2015 to build.