The operator of Japan’s stricken Fukushima Dai-ichi nuclear power plant reported new problems yesterday, including a water leak from a reactor vessel and another spill of contaminated water into the ocean.
The update by Tokyo Electric Power Co (TEPCO) came as emergency crews have been battling to bring the tsunami-hit plant into stable “cold shutdown” some time between October and January.
The giant ocean wave triggered by the March 11 magnitude 9.0 earthquake knocked out the plant’s water cooling systems, leading fuel rods inside several of the reactor cores to partially melt down.
Pressure and temperature buildups have triggered a series of explosions and workers have since doused the reactors and fuel rod pools with water to stop them from overheating and releasing greater amounts of radiation.
TEPCO yesterday said new measurements taken this week, after workers in protective suits fixed gauges in the badly hit Reactor 1 building, indicated that water pumped into the pressure vessel had quickly leaked out.
The water level inside had fallen below the bottom of the fuel rods, suggesting they had been exposed to the air, increasing the risk of a dangerous full meltdown.
However, the vessel’s relatively low outside temperature of 100oC to 120oC indicated that the rods had dropped to the bottom of the vessel and were under water there, TEPCO said.
“The temperature of the pressure vessel was 100 to 120 degrees, which is considered to be the level where the fuel rods are being cooled down in a relatively stable manner,” a TEPCO official said.
TEPCO has been injecting about seven tonnes of water per hour into the Reactor 1 pressure vessel and also plans to flood the wider containment vessel around it to cool down the entire system.
The dousing operations — in which tens of thousands of tonnes of water have been injected with fire trucks, concrete boom pumps and other pumping systems — have created massive amounts of highly contaminated runoff water.
TEPCO has struggled to stop spills into the Pacific Ocean, but reported another one yesterday, saying water had leaked into the sea from a concrete pit near Reactor 3, one of the plant’s six units.
Samples of seawater taken near the plant contained cesium-134 at a concentration 18,000 times the permitted level, the utility said, adding that the spill had been stopped by filling the pit with concrete.
“Today, we have continued to investigate the route of the leakage into the sea and why it happened,” TEPCO spokesman Yoshinori Mori said.
Top government spokesman Yukio Edano called the leak “deplorable” and apologized to the fishing industry and to neighboring countries.