New figures on background radiation levels recorded 60km northwest of the Daiichi power plant have also been released this week by Japanese physicist Tsuneo Konayashi from Fukushima Medical University.

BBC: Fukushima fallout fears over Japan farms

Dr. Yamashita, of Fukushima Medical University, said that, though radiation exposure for the general population has likely been low, evacuations and fear of radiation could lead to problems such as increased consumption of alcohol and stress-related illnesses.

WSJ: In Japan, Relief at Radiation's Low Toll

They were much more optimistic about the outlook for new reactor designs than a panel held at the University of Chicago in the wake of the Fukushima accident.

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Biologists led by radio-ecologist Timothy Mousseau at the University of South Carolina studied 300 locations around Fukushima last July and found that local bird populations had dropped by about a third.

WSJ: In Japan, Relief at Radiation's Low Toll

Such technical difficulties shouldn't prevent Tepco from taking measures to make sure the equipment at Fukushima Daiichi is working, said Tadashi Narabayashi, a nuclear-engineering professor at Hokkaido University.

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