The operator of Japan’s crippled nuclear plant said on Saturday that it is moving tons of highly radioactive water from a temporary storage tank to another after detecting signs of leakage - a blow to the plant struggling with the tight storage space. Tokyo Electric Power Company said an estimated 120 tons of the water are believed to have breached the tank’s inner linings, although little is thought to have leaked into the soil. Tepco is moving the water to a nearby tank - a process that could take several days. Tepco detected the leak earlier this week, when radiation levels spiked in water samples collected in between the inner linings of the tank. Radiation levels in water samples taken outside the tank also have increased, an indication of the water leak, Tepco spokesman Masayuki Ono said. The leak is not only an immediate environmental concern, but threatens Tepco’s tightrope water management situation, he said. The tank contains 13,000 tons of the water, which is part of the water that was used to cool melted fuel at the Fukushima Dai-ichi reactors damaged in the March 2011 disaster. So much water has been used that Tepco is struggling to find storage space. More than 270,000 tons of highly radioactive water is already stored in hundreds of gigantic tanks and another underground tank. They are visible even at the plant’s entrance and built around the compound, taking up more than 80 per cent of its storage capacity. Tepco expects the amount to double over three years and plans to build hundreds more tanks by mid-2015 to meet the demand. Because of that, Tepco is anxious to launch a new water treatment system that can purify the contaminated water. The machine, called ALPS, recently started a final test run after six months of delays due to safety requirements by government regulators. Tepco officials have indicated hopes to release the water into the ocean. Ono said Tepco has no immediate plans to do so without public acceptance. The plant is being decommissioned but continues to experience glitches. A fuel storage pool temporarily its lost cooling system Friday, a month after a similar 30-hour outage. The underground tank, several times the size of an Olympic-size swimming pool and similar to an industrial waste dump, is dug directly into the ground and protected by two layers of polyethylene linings inside the outermost clay-based lining, with a felt padding in between each layer. The meltdowns have caused the plant to release radiation into the surroundings and displaced about 160,000 people from around the plant. They do not know when or if they will be able to return home.