Workers at leaking water tanks at the Fukushima nuclear plant. Japan Pool/ AFP/ Getty Images

Prime Minister Shinzo Abe said Sunday that Japan is open to receiving overseas help to contain widening disaster at the crippled nuclear plant in Fukushima, where radioactive water leaks and other mishaps are now reported almost daily. "We are wide open to receive the most advanced knowledge from overseas to contain the problem," Abe said in his English speech to open the conference on energy and environment at an international science forum in Kyoto in western Japan. "My country needs your knowledge and expertise," he said. Despite Abe's reassurances to the International Olympic Committee last month that the leaks were "under control," many Japanese believe he was glossing over problems at the plant. Abe did not say whether he still thinks the leaks are under control, or give any specifics about foreign participation. His comments come just days after the plant's operator acknowledged that highly contaminated water spilled from a storage tank as workers tried to fill it to the top. The operator of the crippled Fukushima Dai-ichi nuclear plant says at least 110 gallons spilled when workers overfilled a storage tank without a gauge that could have warned them of the danger.

A long list of leaks

The amount is tiny compared to the untold thousands of tons of radioactive water that have leaked, much of it into the Pacific Ocean, since a massive earthquake and tsunami wrecked the plant and sent it into meltdown in 2011. But the error is one of many the operator has committed as it struggles to manage a seemingly endless, tainted flow. Plant operator Tokyo Electric Power Co. (TEPCO) said Thursday workers detected the water spilling from the top of one large tank when they were patrolling the site the night before. The tank is one of about 1,000 erected on the grounds around the plant to hold water used to cool the melted nuclear fuel in the broken reactors. TEPCO said the water then spilled out of a concrete barrier surrounding the tank and believed that most of it reached the sea via a ditch next to the river. The company later said, however, radiation levels in sea water samples taken just off the plant's coast remained below detectable levels. The overspill, the latest of several mishaps in less than a month, prompted the Nuclear Regulation Authority to summon the utility president and reprimand him in public. Katsuhiko Ikeda, administrative head of the agency, ordered TEPCO President Naomi Hirose on Friday to ensure better on-site management and prevent human error, and submit improvement plans in a report. "It is extremely regrettable that contaminated water leaked because of human error," Ikeda said. "We must say on-site management is extremely poor." The new leak is sure to add to public concern and criticism of TEPCO and the government for their handling of the nuclear crisis. In August, the utility reported a 300-metric-ton leak (about 80,000 gallons -- roughly equal to the amount of water used by 200 American families each day) from another storage tank, one of a string of leaks in recent months. That came after the utility and the government acknowledged that contaminated groundwater was seeping into ocean at a rate of 80,000 gallons per day for some time.

'These are not accidents'

TEPCO spokesman Masayuki Ono told an urgent news conference Thursday that the overflow occurred at a 450-ton tank without a water gauge and standing on an unlevel ground, slightly tilting toward the sea. The tank was already nearly full, but workers pumped in more contaminated water into it to maximize capacity as the plant was facing a serious storage crunch. Recent rainstorms that flooded tank yards and the subsequent need to pump up and store contaminated rainwater also added to the shortage, he said. "We could have, and should have, prevented the overflow," he said. TEPCO said the tank and four others in the same area were already filled up to 98 percent of its design capacity, as in many other tanks elsewhere on the plant. Tetsuro Tsutsui, an engineer and expert of industrial tanks, said the latest problem was emblematic of how TEPCO runs the precarious plant. He said it was "unthinkable" to fill tanks up to the top, or build them on tilted ground without building a level foundation. "That's only common sense," Tsutsui, also a member of a citizens group of experts proposing safety measures for the plant. "But that seems to be the routine at the Fukushima Dai-ichi. I must say these are not accidents. There must be a systematic problem in the way things are run over there." Experts have faulted TEPCO for sloppiness in its handling not only of the water management but also in other daily operations. A list of mishaps just over the past few weeks: On Oct. 2, some 4 tons of contaminated rainwater leaked when workers pumped it into a wrong tank that was also nearly full, resulting in most of it seeping into the ground.

On Sept. 27, a water-treatment machine failed hours after resuming a test-run following months-long repairs, clogged up by a piece of rubber lining that got mistakenly left inside the unit. The rubber fragment has since been removed, with the unit back in operation. The unit stalled again Friday after an alarm went off. The cause is still being investigated.

On Sept. 19, a fire-fighting water pipe was damaged during debris removal operations, causing an 80 gallon water leak. Experts have faulted TEPCO for sloppiness in its handling of the water management, including insufficient tank inspection records, lack of water gauges, as well as connecting hoses lying directly on the grass-covered ground. Until recently, only one worker was assigned to 500 tanks in a two-hour patrol.