Operators at the damaged Fukushima Daiichi nuclear plant in Japan have begun pumping highly radioactive water from unit 2 into a waste storage building 800 meters away.

PackBot in Unit 1 Source: TEPCOOf an estimated 25,000 tons of water accumulated in the unit's basement, tunnels and turbine building, Tokyo Electric Power Co. plans to pump about 10,000 tons to the second-floor basement of the storage building by mid-May, according to the Japan Times. The pumping comes after crews readied the building by examining its earthquake readiness, waterproofing rooms and dumping a large volume of water irradiated at low levels from the structure into the sea.

Water soaking basements has prevented further work on damaged cooling systems at three of the plant’s reactors, with dose rates in the most contaminated water at unit 2 in excess of 1,000 millisieverts per hour. A modified barge and other storage containers are en-route to the site. Also Tuesday, Areva announced it will help TEPCO install a system to remove radioactive contaminants from the water as early as the end of next month.

At unit 2, highly contaminated water could be coming from either a leak in the reactor’s containment or from water pumped into its spent fuel tank to prevent overheating. On Monday night, the Japan Times reported, TEPCO said that a sample of water taken from unit 2’s spent fuel tank Saturday contained 160,000 becquerels per cubic centimeter of cesium-134, 150,000 becquerels of cesium-137 and 4,100 becquerels of iodine-131. Robots inspecting buildings at the site attempted to enter unit 2, TEPCO reported Tuesday, but had to turn around when high humidity fogged a video camera lens. Radiation levels at 4.1 millisieverts per hour were detected at the entrance before the mission was abandoned.

Despite the contamination, the International Atomic Energy Agency on Tuesday expressed optimism that levels of radioactive contaminants escaping the plant will continue to drop under a long-term plan for Fukushima Daiichi released by TEPCO over the weekend.

(Photo: A PackBot works in Unit 1 at Fukushima Daiichi. Source: TEPCO)