Highest radiation found at Fukushima No.1 reactor
NHK World English, 27 June 2012
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The highest level of radiation to date has been detected inside the No.1 reactor vessel at the Fukushima Daiichi nuclear power plant.
Tokyo Electric Power Company said it used endoscopes and dosimeters to examine the interior of the reactor on Tuesday. Internal measurements were made for the first time since the accident in March last year.
The utility detected a record level of 10,300 millisieverts per hour
. The measurement was taken 20 centimeters above the surface of a contaminated water puddle in the reactor's suppression chamber. This high level of radiation would be fatal for humans within 50 minutes. No broken parts were identified in the containment vessel during the survey.
1,000 millisieverts per hour was detected about 4 meters above the water surface. The figure is 10 times higher than measured in the No.2 and No.3 reactors.
Workers are expected to engage in clean-up and other tasks mostly at the 4-meter level, which is raising health concerns.
TEPCO official Junichi Matsumoto said he suspects that a higher radiation level in the No. 1 reactor is caused by more fuel rods melting down than in other reactors.
He said robots will be used for damage assessment because it is unsafe for humans to work on site.