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Tuesday, 2 August 2011

Highest radiation to date at Fukushima plant another hurdle for TEPCO

BY HIDENORI TSUhttp://www.asahi.com/english/TKY201108020249.htmlBOYA STAFF WRITER
The Asahi Shimbun
Tokyo Electric Power Co. was struggling to determine the cause of the highest radiation levels detected at the Fukushima No. 1 nuclear power plant since the disaster started March 11.
photoTEPCO said Aug. 1 that radiation levels of at least 10 sieverts per hour, or 10,000 millisieverts per hour, were found at piping connected to the main exhaust tower between the No. 1 and No. 2 reactors at the Fukushima plant.
That level of radiation would mean death if absorbed all at once. TEPCO officials have not yet determined its source.
Monitoring posts around the plant have not detected higher levels of radiation, officials say. But that is no cause for reassurance.
The fact that such high levels of radiation were detected near piping connected to the outer atmosphere is further evidence that radioactive materials have spewed from the crippled reactors at much higher levels than previously believed.
It is possible similar high levels of radiation may be found on the plant grounds. TEPCO workers will have to carefully test for radiation levels, meaning further delays before the plant is brought under control.
Explosions at the No. 1, No. 3 and No. 4 reactors left rubble scattered around the reactors, creating hurdles for plant workers. Unmanned heavy equipment had been used to remove that rubble to reduce the possibility of workers becoming overexposed.
The extremely high level of radiation was detected when workers were testing for radiation near the piping after rubble had been cleared away.
On July 31, a gamma ray camera was used to determine which areas had unusually high levels of radiation. A further test on Aug. 1 found radiation levels of 10 sieverts per hour on the outside of piping that connects to the main exhaust tower.
The three workers tested for radiation, using measuring equipment with a maximum measure of 10 sieverts, which means the actual level of radiation was likely higher.
Because that level of radiation was detected on the outside of the piping, the level inside the piping could be even higher.
The workers were exposed to a maximum level of 4 millisieverts of radiation. The area where the high level of radiation was detected was subsequently made off-limits to workers.
The highest level of radiation detected at the Fukushima plant until now was 4 sieverts per hour, detected in June inside the No. 1 reactor building.

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