The Tokyo Electric Power Co. (TEPCO) said that although the volume of Sunday's leak was small, it may have contaminated some soil and water outside the plant.
"We have determined that a minimal amount of water was feared to have leaked from the tank, although there was no decline in the level of water inside the tank," TEPCO said in a press release. The company also said that it had detected radioactivity in water outside the plant.
The admission comes a day after 120 tons of contaminated water breached the inner lining of a different underground storage tank, also possibly leaking into the ground. TEPCO has been transferring the contaminated water to another storage tank, a process which could take several days.
But Fukushima is already running low on space to store the contaminated water, which is used to cool spent nuclear fuel.
"The impact (from the leak) is not small, as space is already tight," Masayuki Ono, a TEPCO spokesman, told the Associated Press on Saturday. "We need to review our water management plans."
According to the Associated Press, the Fukushima plant has already stored more than 270,000 tons of highly radioactive water, consuming more than 80 percent of the plant's storage capacity. TEPCO anticipates that the amount of contaminated water will double in the next three years. The utility company has plans to meet the storage demand by building hundreds of additional water tanks by mid-2015.
TEPCO also plans to reduce storage need by introducing a purification system, called ALPS, to decontaminate the water. Although company officials have indicated they want to release the purified water in to the ocean, Ono said there were no immediate plans to do so, particularly if there's not public acceptance for such a measure.
On Friday, one of the systems keeping nuclear fuel cool temporarily failed for three hours, the second such failure in three weeks.
On March 11, 2011, a 9.0 earthquake triggered a 15-meter-high tsunami in northeastern Japan, killing over 15,000 people and causing a nuclear meltdown at the Fukushima plant. The nuclear meltdown has displaced about 160,000 people in the area surrounding the plant.
The plant is being decommissioned, a process which could take decades to fully complete.
slk/mz (AP, AFP, Reuters)