TOKYO — Three hundred tons of highly contaminated water have leaked from a storage tank at the ravaged Fukushima Daiichi nuclear power plant on Japan’s Pacific Coast, its operator said Tuesday, raising further concerns over the site’s safety and prompting regulators to declare a radiological release incident for the first time since disaster struck there in 2011.
Workers raced to place sandbags around the leak at the site to stem the spread of the water, a task made more urgent by a forecast of heavy rain for the Fukushima region later in the day. A spokesman at Tokyo Electric Power Co., the plant’s operator, acknowledged that much of the contaminated water had seeped into the soil and could eventually reach the ocean, adding to the tons of radioactive fluids that have already leaked into the sea from the troubled plant.
The leaked water contains levels of radioactive cesium and strontium many hundreds of times higher than legal safety limits, Tokyo Electric said. Exposure to either element is known to increase the risk of cancer.
The company said it had not determined the source of the leak.
“We must prevent the contaminated water from dispersing further due to rain and are piling up more sandbags,” said Masayuki Ono, a spokesman for the operator, also known as TEPCO. But he said much of the water had already been absorbed into the soil, and workers would try to remove some of the soil using shovel cars and other heavy machinery.
TEPCO has acknowledged in recent weeks that leaks of radioactive runoff at the site, about 150 miles north of Tokyo, are at crisis levels. The runoff comes from cooling water that workers are pumping into the damaged cores of the site’s three most damaged reactors, as well as from ground water pouring into the breached basements of those reactors.
“It is going to be very difficult and dangerous for TEPCO to keep on storing all this water,” said Hiroshi Miyano, an expert in nuclear systems design at Hosei University in Tokyo.