Photo/Illutration One of the scenarios for the spewing of radioactive materials from the Tokai No. 2 plant made by Japan Atomic Power Co. (Provided by Ibaraki prefectural government)

MITO--As many as 170,000 residents would be forced to evacuate if a serious accident occurred at Japan Atomic Power Co.’s Tokai No. 2 plant, the only commercial reactor in the greater Tokyo metropolitan area.

The Ibaraki prefectural government on Nov. 28 released the estimate, which Japan Atomic Power calculated for the spewing of radioactive materials in the event of a major crisis at the Tokai plant.

Prefectural officials said this was the first case in the nation of a local government asking a utility operating a nuclear reactor to make such an estimate to assess the effectiveness of evacuation plans.

Among the various estimates, the high evacuation figure is not even the worst-case scenario in the event of a nuclear disaster. 

Evacuation plans are required for an area within a 30-kilometer radius of a nuclear reactor. A total of about 920,000 people reside within such a radius of the Tokai No. 2 plant.

The results of 22 scenarios calculated by Japan Atomic Power under various conditions were released. The major assumption was that a core meltdown had occurred at an online reactor.

One of the two broad conditions then laid out was that emergency equipment, such as alternative power sources, pumper trucks and venting equipment with filters to reduce the spewing of radioactive materials into the air, were all usable.

The other broad scenario was that only the pumper trucks were available.

Various weather conditions and wind directions were added to determine the different scenarios.

All the simulations had the 64,000 or so residents who live within a 5-km radius of the Tokai reactor evacuating immediately as a preventive measure.

Residents living between 5 and 30 km of the reactor would, in principle, be asked to remain indoors. Decisions on whether to evacuate immediately or within a week would be made based on the actual radiation levels that were recorded.

Under the scenario that all emergency equipment were in working order, the scenario concluded that no resident living within 5 and 30 kilometers would have to evacuate.

But if only pumper trucks were available, the wind was blowing in a southwesterly direction and rain fell for an extended period, about 105,000 residents living within 5 to 30 km would have to temporarily evacuate.

Adding the 64,000 residents living within 5 km who would have to evacuate immediately, the number of evacuees totals about 170,000.

But this was not the worst-case scenario because as one prefectural official noted, “If even pumper trucks could not be used, there is the possibility that more people who live beyond a 30-km radius would have to evacuate.”

Prefectural officials said a precondition of the simulation was to only use situations that would limit the need for evacuation to within the 30-km radius.

(This article was written by Ryo Sasaki and Morio Choh.)

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