Japan's crippled nuclear power plant is struggling to find space to store tens of thousands of tons of highly contaminated water used to cool the broken reactors, the manager of the water treatment team said.

About 200,000 tons of radioactive water - enough to fill more than 50 Olympic-sized swimming pools - are being stored in hundreds of gigantic tanks built around the Fukushima Dai-ichi plant. Operator Tokyo Electric Power Co. has already chopped down trees to make room for more tanks and predicts the volume of water will more than triple within three years.

"It's a pressing issue because our land is limited and we would eventually run out of storage space," the water-treatment manager, Yuichi Okamura, told The Associated Press in an exclusive interview this week.

TEPCO is close to running a new treatment system that could make the water safe enough to release into the ocean. But in the meantime its tanks are filling up - mostly because leaks in reactor facilities are allowing ground water pour in.

Outside experts worry that if contaminated water is released, there will be lasting impact on the environment. And they fear that because of the reactor leaks and water flowing from one part of the plant to another, that may already be happening.