In a development that should improve working conditions and the stability of the unit, TEPCO announced Tuesday that a new cooling system for the spent-fuel tank of Fukushima Daiichi unit 2 is now fully functional.
As with other units at the blacked-out plant following Japan's massive March 11 earthquake, unit 2's spent fuel tank has threatened to overheat in the absence of normal cooling systems. TEPCO had resulted to pouring water into the tanks from the outside, which likely contributed to the large volume of radioactive water accumulating in the plant's lower levels. Conditions in unit 2 were made worse by steam from the tank and humidity levels that at one point were high enough to fog up the camera lenses of robots inspecting its buildings.
The new system is now circulating water in the tank to draw off decay heat from the spent fuel. Kyodo news quoted a TEPCO spokesman as saying that water temperatures should fall from between 70 and 80 C to about 40 C over the next month. Plans call for circulation systems to be complete for units 1 and 3 later this month, and for unit 4 in July.
Also Tuesday, TEPCO reported an oil leak in the artificial bay adjacent to the plant. Government officials said a small amount of oil extended 200 to 300 meters inside the bay and has been contained by a barrier. The leak is believed to originate near the water intakes for units 5 and 6 from pipes connected to oil tanks that were being filled by a tanker when the earthquake hit.