Tokyo, Japan: The US shared detailed map of radiation measurements with Japan in the early days of the 2011 Fukushima Daiichi nuclear disaster that the Japanese government did not make public or use in conducting evacuations, New York Times reported.
The report stated that on March 17, 2011, as residents fled from the areas around the tsunami-stricken Fukushima Daiichi nuclear power plant, the US sent aircraft to measure radiation levels in the vicinity.
The Energy Department then used the data, collected from over 40 hours of flight time over Fukushima, to compile a detailed map that showed an area of high radiation extending northwest from the plant. Measurements “show an area of greater radiation extending northwest from the accident,” materials accompanying the map warned. “This area may be of interest to public safety officials and responders.”
According to Japanese officials, the United States government shared the data with Japan’s Foreign Ministry through its embassy in Tokyo on March 18, a day after helicopters frantically dropped water on a blown-out reactor building to keep spent fuel rods there from overheating.
The Foreign Ministry immediately alerted the nuclear safety agency to the radiation readings, according to Masaru Sato, director of the ministry’s international press division.
But it is unclear what happened next. There is no indication that the nuclear safety agency shared that data with Naoto Kan, the prime minister at the time, or other high-ranking officials, or that it used the maps to guide evacuations.
The Foreign Ministry also shared the data on March 20 with Japan’s Ministry of Education, Culture, Sports, Science and Technology, which is responsible for monitoring radiation levels. But instead of using and publicising the data, the technology ministry asked the Foreign Ministry to confirm that the United States approved of the data being made public, Sato said.
The Foreign Ministry relayed that question to the United States Embassy. Three days later, on March 24, Japan received assurances that the data could be made public.
By that time, some evacuees had already fled northwest, into the path of the radioactivity. And it took the Japanese government another month, and its own testing of radiation levels, to start evacuating contaminated areas outside the 12-mile zone — areas like the town of Namie and the village of Iitate, which had been clearly visible in the Energy Department’s initial maps.