Japanese Government Group Says SPEEDI Unreliable

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A government commission evaluating guidelines on nuclear disaster management released a plan Wednesday asking authorities to refrain from using SPEEDI, a computer system that judges whether residents should evacuate based on its predictions of radioactive fallout after a nuclear accident.

Under current guidelines, evacuations will be ordered when exposure to radioactivity is expected to reach at least 50 millisieverts, based on SPEEDI predictions and accident circumstances.  The SPEEDI system has cost more than 13 billion yen in development and maintenance expenses.

The SPEEDI systems key failures were that it was unable to get information related to reactor cores at the site of the accident and made calculations based on the input of provisional data.  This allowed for even less reliability in the accuracy of the information produced.

It was also shown that the SPEEDI system was unable to make any accurate predictions regarding the area of radioactive contamination as the materials dispersed during the accident changed frequently due to changes in wind direction.

The working group of the Cabinet Office‘s Nuclear Safety Commission said, “Predictions made by SPEEDI have a large degree of uncertainty, making it unreliable during times of emergency.”

Toshimitsu Honma, chief of the group and director of the Nuclear Safety Research Center, said if the system has no information on the time when radioactive material is released and the quantity dispersed, SPEEDI “can predict nothing more than wind direction.”

Source: Yomiuri

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