SPEEDI, a computer simulation system used to determine or predict dispersions of radioactive substances, is supposed to be utilized during a nuclear disaster to help people evacuate to safe areas.
But in the early stage of the crisis at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant, the government did not make public the predictions made by SPEEDI. In the absence of relevant information, some people fled to places where radiation levels were actually higher.
On July 27, the education and science ministry, which is in charge of SPEEDI, issued a report based on a probe of its handling of SPEEDI data. The report attempted to justify the ministry's decision to withhold SPEEDI-based predictions of the dispersion of radioactive fallout from Fukushima No. 1.