Strong Radiation Levels Exceeding Expectations Detected at Fukushima Nuclear Plant

[Image source=AP Yonhap News]

[Asia Economy Reporter Kwon Jae-hee] Stronger radiation than initially estimated by authorities was measured in the containment vessel of Japan's Fukushima Daiichi Nuclear Power Plant, where the Great East Japan Earthquake occurred in March 2011.

According to the Asahi Shimbun on the 15th, the Nuclear Regulation Authority of Japan announced that the radiation level near the surface of the lid at the top of the containment vessel of Reactor No. 2 at Fukushima Daiichi Nuclear Power Plant was confirmed to be 1.2 sieverts per hour, exceeding the initially assumed level.

The lid is circular with a diameter of about 12 meters and a thickness of about 60 cm, made of reinforced concrete, and is installed in three overlapping layers to block radiation coming from the reactor core.

The Nuclear Regulation Authority used a remote-controlled robot to drill a hole about 7 cm deep into the surface of the first lid to measure the radiation level, recording 1.2 sieverts per hour at a depth of about 4 cm near the center.

The Nuclear Regulation Authority believes that a large amount of radioactive cesium released during the accident is attached between the first and second lids, and initially estimated that the radiation dose from the contamination source inside the lid would be about 10 sieverts per hour.

This dose is lethal to a person if exposed for about one hour at close proximity.

However, in light of the recent measurement results, the actual dose from the contamination source is analyzed to be tens of sieverts per hour, much higher than initially estimated.

The lid weighs about 150 tons per sheet and the radiation level is stronger than initially thought, so dismantling work is expected to be complicated.

Tokyo Electric Power Company explained, "We will review construction methods assuming severe contamination areas," and Asahi predicted that changes to the decommissioning plan may be necessary.