Fukushima Daiichi Nuclear Plant Weekly Review

Regulators in Japan continue to refine their approach to a massive cleanup project following the March accident at the Fukushima Daiichi nuclear power plant. Meanwhile, the government reported it does not suspect radiation detected in Tokyo came from the plant.

Developments at Fukushima over the last week include:

Unit 1 Dose Levels Down

Fukushima Unit 1 reactor building. Source: TEPCOOn Tuesday, TEPCO said air samples from inside the reactor building of unit 1 indicated contaminant levels there have fallen to roughly 10 percent of the legal exposure limit for workers.

Concentrations of cesium 134 and cesium 137 were measured recently at between 0.001 and 0.0001 becquerels per cubic centimeter, the Mainichi Daily News quoted the Japanese utility as saying. Concentrations of iodine 131 had fallen below measurable levels.

Radiation Scare in Tokyo Likely Unrelated to Fukushima

Radiation detected on a fence left many Tokyo residents fearful in recent days that contamination from the plant had reached the city. But further analysis by scientists indicated the substance is likely radium-226, an isotope that is not present in power reactors.

The city's Setagaya Ward measured a dose of 2.707 microsieverts per hour at the fence Oct. 6, the Japan Times reported. The ward is also investigating elevated radiation readings from bottles containing an unknown substance in a basement near the fence. The radiation appears to be limited to one specific site, though, and its location is not consistent with contamination carried by wind and rain, as would be the case with contamination from Fukushima. The radiation levels detected did not call for an evacuation, and officials will study the sites further before decontaminating them.

Government Sets March 2014 Cleanup Target for Evacuation Zone

A draft cleanup plan by the Environment Ministry aims to remove contaminated soil from evacuation zones around the Fukushima plant in 2 ½ years.

The Daily Yomiuri reported Wednesday that the government will also take responsibility for the disposal of material containing more than 8,000 becquerels per kilogram of cesium removed from areas both inside and outside evacuation zones.

Photo: Workers inspect a reactor pressure vessel spray system component inside unit 1 on Sunday. Source: TEPCO

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