According to Singapore-based news outlet AsiaOne, the Tokyo Electric Power Co., which owns the multi-nuclear reactor power station at Fukushima, announced April 6 that some 120 tons of water that had been contaminated with radioactive substances had leaked from an underground storage facility at the No. 1 atomic power plant site.
Running out of storage room?TEPCO officials announced the leak late in the day April 5, a Friday, "but said measures to address the problem had not been taken for two days because the cause had not been identified," AsiaOne reported. The company "assumed the water was still leaking."
According to company officials TEPCO estimates that the leaked water contains about 710 billion becquerels of radioactive substances, making it the largest leak of radioactive materials ever at the plant. Discovery of the leak led the company to transfer about 13,000 tons of polluted, radioactive water in the questionable storage area to a neighboring underground storage unit.
That storage unit, TEPCO said, is 60 meters long, 53 meters wide and six meters deep. It is pool-like in structure and has a three-layer waterproof sheet with a concrete cover.
According to the company, water that has leaked from damaged nuclear reactors is run through filters and additional devices in order to remove radioactive elements. The water is then stored in facilities for low-level contaminated water.
TEPCO began using the storage facility Feb. 1. As of April 5, 13,000 tons of radioactive water was being stored there - very close to the 14,000-ton limit.
More leaking contaminationAsiaOne reported that water samples taken by TEPCO from soil surrounding the damaged facility a few days later showed 35 becquerels per cubic centimeter of radioactive substances, which is abnormal. "Safe" levels of becquerels is 300 per kilogram of water, according to New Scientist.
However, TEPCO officials did not publicly announce their findings right away after not finding any other unusual changes in water quality data, such as chloride concentration.
On April 5, the report said, two days after the problem was first noticed, water with 6,000 becquerels per cubic centimeter of radioactive substances was located between the first and second layers of the waterproof sheet, which alerted TEPCO engineers and plant officials that a leak had occurred.
As the sheet's layers were joined when the facility was constructed, TEPCO assumed that the sheet may have been damaged, or that a mistake had been made during construction. An average of about 400 tons a day of groundwater seeped into buildings housing nuclear reactors and turbines, increasing the quantity of polluted water.
The latest problem will create a storage shortage; TEPCO officials said storage of polluted water at the facility will be reduced from 53,000 tons to 40,000 - a significant reduction. That will make it necessary for the power company to go over procedures for handling polluted water, which will include increasing the number of storage units.
The disaster that keeps on givingTEPCO said earlier this month it expected the water transfer would take about five days to complete.
"As the height of the water storage facility is relatively low, we think it's unlikely that the polluted water mixed into underground water and reached the sea 800 meters away," said Masayuki Ono, the acting chief of TEPCO's nuclear facilities department, at a press conference April 6.
The plant was damaged by a huge earthquake-caused tsunami March 11, 2011. At the time of the incident, three of the plant's atomic reactors were shut down: No. 4 had been de-fueled and Nos. 5 and 6 were in cold shut-down for maintenance.
The remaining three automatically shut down at the time of the accident and emergency generators came on to keep coolant systems operating.