The difficult task of pumping highly radioactive water out of the basement of a turbine building at a damaged Japanese nuclear power plant began Tuesday, but officials cautioned that the work would be slow and difficult.
The Japanese government, meanwhile, said it was considering a plan to further restrict access to the evacuated area within 12 miles of the plant, the Fukushima Daiichi Nuclear Power Station. Some families have been re-entering the area to remove belongings, and dozens of people have never left.
At the plant itself, the Tokyo Electric Power Company said that it planned to pump 10,000 metric tons of water into a storage building at a rate of 480 tons a day, which would take nearly three weeks. The company is still working on ways to remove an additional 57,500 tons of heavily contaminated water at the same building, next to Reactor No. 2, and at other nearby buildings.
The cautious pace of the pumping and the volume of water to be moved are further signs of the complexity of the undertaking that faces Tokyo Electric. Removing the water is one of the 63 tasks that the company outlined Sunday in its plan to fully shut down the stricken reactors, halt all releases of radioactive material and restore reliable cooling and electricity roughly by the end of the year.
Michael Friedlander, a former senior nuclear power plant operator in the United States, said that while the pumping might be proceeding slowly, a faster pace could prove dangerous.
“If a pipe breaks and you’re pumping hundreds of gallons a minute, you’re going to make a huge mess,” he said.
Hidehiko Nishiyama, the deputy director general of Japan’s Nuclear and Industrial Safety Agency, said that the heavily contaminated water that had accumulated in basements and trenches at the site is two million times as radioactive as the less contaminated water that workers pumped into the ocean from April 4 to April 10. Workers pumped 10,393 tons of the less contaminated water into the ocean in order to make room in storage areas for the far more highly radioactive water from inside the reactor buildings.
Pumping contaminated water into the ocean has provoked considerable dismay from Japanese fishermen and from nearby countries, particularly South Korea and China. Mr. Nishiyama said Tuesday that Japan had no plans and no need to do so anymore.
Plans are being made for the installation of water-purification equipment and heat exchangers so that the same water can be pumped repeatedly through the reactors.
Anne Lauvergeon, the chief executive of Areva, France’s nuclear-power equipment provider, said at a news conference in Tokyo on Tuesday evening that it would probably take until the end of May to set up a water treatment station at the plant. Once running, she said, it should be able to handle 50 metric tons of water an hour and should almost entirely remove the radiation.
The technology, called “co-precipitation,” uses chemical agents to remove radioactive elements from water. The treatment station itself will be provided by Veolia Water, a British water and waste management service. Areva and Tokyo Electric have not discussed the cost of the services, Ms. Lauvergeon said.
Areva, together with Veolia Water, will also provide three lines of desalination equipment to enable Tokyo Electric to convert seawater into fresh water for cooling the reactors. Fresh water provides better cooling; the spaces between the fuel rods have started to become congested with salt from seawater.
She also said that Areva was not preparing an overall plan to decommission the troubled plant, though she said the company was prepared to cooperate with any long-term process to eventually dismantle Fukushima Daiichi. Toshiba and Hitachi have submitted competing plans to dismantle the plant; the work could take decades.
In a further effort to improve cooling, Mr. Nishiyama said Tuesday that a decision had been made to flood the primary containment vessels of the No. 1 and No. 3 reactors with enough water to cover up the sides of the reactor pressure vessels up to the level of the uranium fuel rods.
This was not done sooner because only now have workers been able to determine that the primary containment vessels are sufficiently watertight. The vessel at the No. 2 reactor is damaged and leaking gases, and the leak or leaks need to be plugged before it can be flooded, Mr. Nishiyama said.
The No. 2 reactor has posed some of the greatest challenges in recent days, including another leak that spewed radioactive water until plugged two weeks ago.
Robots entered Reactors Nos. 1 and 3 on Sunday and measured the radiation inside. But when two robots entered Reactor No. 2 on Monday, the steam inside was so dense that a robot mounted with a camera was unable to get a clear image of a radiation sensor carried by the other robot, Japanese officials said.
Ken Ijichi, Moshe Komata and Kantaro Suzuki contributed reporting.
This article "Water Pumping Begins at Japan Nuclear Reactor" originally appeared at The New York Times.