The operator of Japan’s crippled Fukushima nuclear plant says rods inside one of the reactors have most likely melted after being fully exposed.
The Tokyo Electric Power Company (TEPCO) has reported a leak from the reactor vessel and another spill of contaminated water into the ocean.
The company says the water level inside reactor No. 1 was much lower than it thought, exposing about 1.5 metres of the fuel rods.
It says the rods have likely melted and workers are still trying to cool them in water at the bottom of the pressure vessel.
The company believes that about half the reactor core in reactor No. 1 has been damaged and has been pumping in up to eight tonnes of water an hour into the pressure vessel to try to keep the rods cool.
The update comes as emergency crews battle to bring the tsunami-hit and radiation-leaking plant into stable “cold shutdown” sometime between October and January.
The giant ocean wave triggered by the magnitude-9.0 quake on March 11 knocked out the plant’s water cooling systems, leading fuel rods inside several of the reactor cores to partially melt down.
TEPCO says new measurements taken this week, after workers in protective suits fixed gauges in the badly hit reactor No. 1 building, indicate that water pumped into the pressure vessel had quickly leaked out.
The water level inside had fallen below the bottom of the four-metre-long 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 100-120 degrees Celsius indicated that the rods had dropped to the bottom of the vessel and were under water there, TEPCO said.
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 run-off water.
TEPCO has struggled to stop spills into the Pacific Ocean and has now reported another, saying water had leaked into the sea from a concrete pit near reactor No. 3, one of the plant’s six units.
Samples of seawater taken near the plant contained caesium-134 at a concentration 18,000 times the permitted level, the company said, adding that the spill had been stopped by filling the pit with concrete.
“We have continued to investigate the route of the leakage into sea and why it happened,” TEPCO spokesman Yoshinori Mori said.
Top government spokesman Yukio Edano called the leak “deplorable” and apologised to the fishing industry and to neighbouring countries.
