Fresh Fukushima leak may contaminate ocean

The danger from Japan's Fukushima nuclear power plant, shattered by the earthquake and tsunami in March, is far from over. Large quantities of highly radioactive water have leaked through a crack in the wall of a treatment facility and some may have drained into the ocean, the plant's operator Tokyo Electric Power (Tepco) said today.

The leak indicates the difficulties facing Tepco as it tries bring the damaged Dai-ichi-owned nuclear power plant to a cold shutdown by year's end.

The company said as much as 45 tonnes of radioactive water had leaked through the wall. It has piled up sandbags to prevent further leaks but fears some water may have already found its way into a gutter that connects to the Pacific Ocean about 600m away.

A pool of radioactive water was discovered midday Sunday around a decontamination device, Tepco said in a statement on its website. After the equipment was turned off, the leak appeared to stop. Later, workers found a crack in a concrete barrier leaking the contaminated water into the ocean gutter.

The pooled water around the purification device was measured on Sunday at 16,000 bequerels per liter of cesium-134, and 29,000 bequerels per liter of cesium-137, Tecpo said. That's 270 times and 322 times higher, respectively, than government safety limits, according to the Citizens' Nuclear Information Center in Tokyo.

Cesium-137 is dangerous because it can last for decades in the environment, releasing cancer-causing radiation. The half-life of cesium-134 is about two years, while the half-life of cesium-137 is about 30 years.