Extremely high radiation levels were detected in a second area on the grounds of the Fukushima No. 1 nuclear power plant, Tokyo Electric Power Co. said Aug. 2.
The area is close to the spot where radiation levels of 10 sieverts or more per hour were found on Aug. 1, the highest levels recorded since the March 11 Great East Japan Earthquake and tsunami triggered the nuclear crisis.
TEPCO said levels at the second area could possibly exceed 10 sieverts per hour.
The second spot, 10 meters above ground and only a few meters from the first spot, is along piping used to vent gases to lower pressure within the containment vessel in case of emergency.
In addition, TEPCO said radiation levels exceeding 5 sieverts per hour were found inside the air-conditioning room on the second floor of the No. 1 reactor building. The building is connected to the two outdoor spots via the piping system.
Those levels are the highest recorded indoors so far.
TEPCO released photos of the outdoor areas, which were near the bottom of an exhaust stack that stands between the No. 1 and No. 2 reactor buildings.
“It is possible that radioactive substances, derived from fuel rods that melted inside the nuclear reactor, were carried through the piping and adhered to its inner walls when gases were vented during the early phase of the crisis,” said Junichi Matsumoto, acting general manager of TEPCO’s Nuclear Power and Plant Siting Division.
The high radiation levels were discovered when a gamma ray camera, which can locate sources of high radiation, was used on July 31 to survey the area. Precise radiation levels were not available at the second spot because it lay beyond the reach of the dosimeter.