Fresh radioactive leak at Fukushima raises global concerns

About 3,175 gallons of highly radioactive water has overflowed into the ground from a storage tank at Japan's crippled Fukushima nuclear power plant, though the spill did not reach the Pacific Ocean.

This is one of the worst incidents since last August, when a series of radioactive leaks sparked international alarm.

The Tokyo Electric Power Company (TEPCO), which operates the plant, said a worker found water overflowing from a tank during a routine patrol of the site devastated by a 2011 earthquake and tsunami.

A valve had remained open by mistake and sent too much contaminated water into a separate holding area at the plant some 130 miles north of Tokyo, TEPCO added.

Radioactive substances measuring 230 million becquerels per litre, including the radioactive isotope strontium 90, were discovered in the ground nearby. The legal limit for releasing strontium 90 into the ocean is 30 becquerels per litre.

TEPCO said the leak involved partially treated water from early in the disaster at the plant, meaning it was more toxic than previous leaks.

"We apologize for worrying the public with such a leak," TEPCO spokesman Masayuki Ono told in Tokyo, adding that it was unlikely that the water had spilled into the nearby sea because there were no waterways leading into the sea.

The valves have since been shut and TEPCO is currently extracting the contaminated soil from the plant that suffered three nuclear meltdowns after the quake and tsunami, the company said.

The utility has been harshly criticized for its response to the three nuclear meltdowns following the quake and tsunami. Last week, a nuclear regulatory official said Tepco delayed release of record-high measurements of strontium-90 in groundwater despite repeated requests by the regulator.

The cores of three reactors melted at the Fukushima Dai-ichi plant in 2011 following a massive earthquake and tsunami, and radioactive water has since then been stored in more than 1,000 tanks.

The incident once again throws into stark doubt India's increasing push for mega-nuclear plants,  even as the developed world moves away from nuclear to safer energy sources.