Radiation levels keep repair workers at bay

TOKYO – A pair of robots sent to explore buildings inside Japan’s crippled nuclear reactor came back Monday with disheartening news: Radiation levels are far too high for repair crews to go inside.

Nevertheless, officials remained hopeful they can stick to their freshly minted “roadmap” for cleaning up the radiation leak and stabilizing the Fukushima Dai-ichi plant by year’s end so they can begin returning tens of thousands of evacuees to their homes.

“Even I had expected high radioactivity in those areas. I’m sure (plant operator Tokyo Electric Power Co.) and other experts have factored in those figures when they compiled the roadmap,” Chief Cabinet Secretary Yukio Edano said.

Officials said Monday that radiation had spiked in a water tank in Unit 2 and contaminated water was discovered in other areas of the plant. They also described in more detail the damage to fuel in three troubled reactors, saying pellets had melted.

Workers have not been able to enter the reactor buildings at the stricken plant since the first days after the cooling systems were wrecked by the March 11 earthquake and tsunami that left more than 27,000 people dead or missing. Hydrogen explosions in both buildings in the first few days destroyed their roofs and scattered radioactive debris.

On Sunday, a plant worker opened an outer door to one of the buildings and two Packbots, which resemble drafting lamps on tank-like treads, entered. After the worker closed the door, one robot opened an inner door and both rolled inside to take readings for temperature, pressure and radioactivity. They later entered a second building.

The robots reported radioactivity readings of up to 49 millisieverts per hour inside Unit 1 and up to 57 inside Unit 3, levels too high for workers to safely enter.

“It’s a harsh environment for humans to work inside,” said Hidehiko Nishiyama of Japan’s Nuclear and Industrial Safety Agency.

Workers in the U.S. nuclear industry are allowed an upper limit of 50 millisieverts per year.

The robots, made by Bedford, Mass., company iRobot, which also makes the Roomba vacuum cleaner, explored Unit 2 on Monday, but TEPCO officials had yet to analyze that data.