TOKYO - Tokyo Electric Power Co. said Thursday that one of the reactor cores at its stricken Fukushima Dai-ichi nuclear plant is more seriously damaged than previously thought, setting back the utility's plan to resolve the crisis.
Fuel rods in the core of the No. 1 reactor are fully exposed, with the water level 3.3 feet below the base of the fuel assembly, Junichi Matsumoto, a general manager at the utility known as Tepco, told reporters at a briefing in Tokyo. Melted fuel has dropped to the bottom of the pressure vessel and is still being cooled, Matsumoto said.
Japan is trying to contain the worst nuclear disaster since Chernobyl after a quake and tsunami two months ago knocked out power and cooling systems at the Fukushima station. While authorities have previously suspected a partial meltdown at Unit 1, high radiation levels had prevented workers from entering the building to check the damage until last week.
"What this means is this is probably going to be a much more difficult cleanup than they originally planned for," said Paul Padley, a particle physicist at Rice University in Houston. The government and Tepco "have consistently appeared to be underestimating the severity of the situation."
There's no danger of another explosion like the one that blew the roof off the reactor in March, Matsumoto said at the briefing.