Japan expects to bring the reactors at the Fukushima Daiichi nuclear plant under control sooner than previously expected, government officials said Tuesday, although new problems have emerged over the large amounts of radioactive water in the basements of the units, complicating longer-term efforts to clean up the site.

Tokyo Electric Power Co. (9501.TO) said in its monthly review of its nine-month plant stabilization plan that emissions of radioactive materials from the plant have been reduced to a maximum of 1/4,000,000th of the peak, due to the recent cooling of the reactors that has reduced the amount of tainted steam escaping into the atmosphere.

"By reducing emissions of radioactive materials, we hope to make it possible for evacuees to return to their homes as early as possible," said Yasuhiro Sonoda, a lower house member responsible for managing the Fukushima crisis.

Trade and industry minister Yukio Edano said that "there is a reasonable chance" of bringing the damaged reactors to a cold shutdown by the year end," which would be one month ahead of the schedule under the master "roadmap." His comments echoed statements on Monday by environment minister Goshi Hosono at an annual general meeting of the International Atomic Energy Agency.

Cold shutdown refers to a reactor being in a stable condition with the core temperature below 100 degrees Celsius.

The more rapid cooling was made possible by repairs to the core spray line that allows sprinkling water directly over the reactor core. The repairs had been made in highly difficult conditions for the workers since high radiation levels are still present at the reactors.

But a new problem emerged in the longer-range project to remove highly radioactive water from the basements of the reactor buildings, which is necessary to seal leaks and thereby permanently deal with radioactive materials.

According to Tepco, despite steady decontamination through filtering, the amount of water has not decreased as much as expected, apparently due to recent heavy rainfall and seepage of groundwater into the basements, which hold pumps and other machinery.

Japan has been hit by an unusually large numbers of storms this summer. Typhoon Roke, the 15th storm in this year's typhoon season, is expected to reach the country's main island of Honshu midday Wednesday, the Japan Meteorological Agency said. The agency forecasts approximately 500 millimeters of rainfall will inundate large swathes of the country over the next 24 hours.

In the past month, the amount of water in the basements decreased by only 15,000 cubic meters, despite the fact that 40,000 cubic meters of contaminated water has been treated.

"The seepage of groundwater won't require us to change the roadmap plan," said Junichi Matsumoto, Tepco spokesman on nuclear issues.

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