Nuclear Meltdown

Robot in Japanese reactors detects high radiation

(Agencies)
Updated: 2011-04-18 13:30

remote-controlled robot called "Packbot", which has capabilities including manoeuvring through buildings, taking images, and measuring radiation levels, opens a door at Tokyo Electric Power (TEPCO) Co's crippled Fukushima Daiichi Nuclear Power Plant No.3 reactor building in Fukushima, northern Japan April 17, 2011, in this handout photo released by TEPCO. Japan's Tokyo Electric Power said on Sunday it hoped to achieve a "cold shutdown" of its crippled Fukushima Daiichi nuclear plant in six to nine months, setting a timeframe for bringing the world's worst nuclear crisis in 25 years under control. [Photo/Agencies]

TOKYO - Readings Monday from a robot that entered two crippled buildings at Japan's tsunami-flooded nuclear plant for the first time in more than a month displayed a harsh environment still too radioactive for workers to enter.

Related readings: Radioactivity rises in sea off Japan nuclear plant  Japan detects higher radiation levels in nuke plant

Nuclear officials said the radiation readings for Unit 1 and Unit 3 at the tsunami-flooded Fukushima Dai-ichi plant do not alter plans for stabilizing the complex by year's end under a "road map" released by the plant operator Sunday. Workers have not gone inside the two reactor buildings since the first days after the plant's cooling systems were wrecked by a catastrophic earthquake and tsunami on March 11. Hydrogen explosions in both buildings in the first few days destroyed their roofs and littered them with radioactive debris.

A US-made robot that looks like a drafting lamp on treads haltingly entered the two buildings Sunday and took readings for temperature, pressure and radioactivity. More data must be collected and radioactivity must be further reduced before workers are allowed inside, said Hidehiko Nishiyama of Japan's Nuclear and Industrial Safety Agency.

"It's a harsh environment for humans to work inside," Nishiyama said.

It is still possible, he said, to achieve plant operator Tokyo Electric Power Co's goal of achieving a cold shutdown of the plant within six to nine months as laid out in a timetable the company announced Sunday.

"I do believe we must be creative to come up with ways to achieve our goals," Nishiyama said. "I still think the plan ... is as appropriate as we can get at the moment."

TEPCO official Takeshi Makigami said the robots must pave the way for workers to be able to re-enter the building. "What robots can do is limited, so eventually, people must enter the buildings," Makigami said. The robot was set to investigate Unit 2 later Monday.

As work continues inside the plant to reduce radiation levels and stem leaks into the sea, the Defense Ministry said it would send about 2,500 soldiers to join the hundreds of police, outfitted with protective suits, who are searching for bodies in tsunami debris around the plant.

Around 1,000 bodies are thought to be buried in the muddy piles of broken houses, cars and fishing boats. As of Sunday, searchers had located 66 bodies and recovered 63, police said.

The combined earthquake and tsunami have left more than 27,000 people dead or missing.

The robots being used inside the plant, called Packbots, are made by Bedford, Massachussetts company iRobot. Traveling on miniature tank-like treads, the devices opened closed doors and explored the insides of the reactor buildings, coming back with radioactivity readings of up to 49 millisieverts per hour inside Unit 1 and up to 57 millisieverts per hour inside Unit 3.

The legal limit for nuclear workers was more than doubled since the crisis began to 250 millisieverts.

The US Environmental Protection Agency recommends an evacuation after an incident releases 10 millisieverts of radiation, and workers in the US nuclear industry are allowed an upper limit of 50 millisieverts per year. Doctors say radiation sickness sets in at 1,000 millisieverts and includes nausea and vomiting.