Peak radiation spots found at Fukushima plant

Operator Tepco finds pockets of radiation at the Fukushima Daiichi plant so high they could kill a person after just several seconds.

Tim Hornyak
Crave freelancer Tim Hornyak is the author of "Loving the Machine: The Art and Science of Japanese Robots." He has been writing about Japanese culture and technology for a decade. E-mail Tim.
Tim Hornyak
2 min read
The red spots in this image from a gamma camera show areas outside the Fukushima plant where radiation exceeds 10 sieverts per hour, which can be almost instantly lethal. Tepco

Japan's struggle to contain a nuclear power plant crippled in the March 11 earthquake and tsunami has had another setback as record-high radiation levels at the site have been detected.

Radiation levels at least 5 sieverts per hour were detected on the second floor of the No. 1 reactor building at the Fukushima Daiichi nuclear plant in Japan, the highest detected indoors at the plant since the quake and tsunami, operator Tokyo Electric Power Company said this week.

The previous highest dose detected indoors there was 4 sieverts per hour in the No. 1 reactor building.

The beleaguered utility also reported pockets of radiation measuring at least 10 sieverts per hour outdoors at the bottom of a ventilation stack between two reactors. Exposure to more than 10 sieverts per hour could kill or seriously sicken a person after just several seconds.

In both the indoor and outdoor readings, the levels were actually beyond the measuring capacity of the separate detection equipment used.

The maximum exposure level allowed for workers at the plant is 250 millisieverts of radiation per year. In 1999, a nuclear worker died of organ failure after being exposed to an estimated 17 sieverts of radiation in the Tokaimura nuclear accident in Japan, which occurred at a uranium reprocessing facility run by JCO.

Tepco said the spots of high radiation at the Fukushima Daiichi plant, now off-limits, do not reflect an overall rise in radiation at the complex. The lethal radiation pockets could be the result of emergency venting conducted at the plant just after the disaster.

"The high dose was discovered in an area that doesn't hamper recovery efforts at the plant," Reuters quoted Tepco spokesman Junichi Matsumoto as saying.

The utility still plans to stabilize Fukushima Daiichi by January. But it could still take decades to fully dismantle the plant.