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.
What is deplorable is that there is no evidence that ministry officials ever seriously considered utilizing SPEEDI to help residents safely escape the radiation danger. The ministry’s organizational culture of irresponsibility is highlighted by the fact that the probe could not even determine whether ministry officials held discussions on the question of whether SPEEDI-based predictions should be disclosed for evacuation purposes. If someone feels that a cover-up is going on in the ministry, he or she cannot be blamed.
SPEEDI — short for System for Prediction of Environmental Emergency Dose Information — is the same system that the Nuclear Safety Commission uses to make risk calculations. It divides the nation into a fine geographic grid of 250-by-250-meter squares to predict how radioactive materials will spread in the event of a disaster at a nuclear power plant.
The ministry could have used SPEEDI to keep the public informed of the geographical distribution of nuclear substances released by Fukushima No. 1, along with the radiation levels, and what the distribution of radioactive substances and radiation levels might be if the situation at the plant worsened.
The ministry report stated that because information on real conditions at the reactors was lacking, the accuracy of SPEEDI predictions on the distribution of radioactive substances could not be known. But attention should be paid to the fact that the government commission to investigate the Fukushima nuclear crisis stated that even though the amount of radiation released per unit area was not known, SPEEDI-based predictions could have been used to enhance the safety of those residents forced to evacuate.
If hypothetical amounts of radioactive substances released from the reactors had been fed into SPEEDI in the absence of real data, SPEEDI could have predicted the directions in which radioactive materials would disperse.
It has been known that the education and science ministry utilized SPEEDI-based predictions in choosing the points in Fukushima Prefecture for measuring radiation levels and provided SPEEDI-based predictions to the U.S armed forces.
Given these facts, it is not far-fetched to say that from the very beginning, the ministry had no intention of using SPEEDI for the sake of protecting local residents from radiation hazards.
