OTSU--Shiga Prefecture, despite its proximity to the nation's largest concentration of nuclear reactors, has been denied access by the science ministry to a key computer simulation program that would allow it to prepare better for nuclear disaster.
OTSU--Shiga Prefecture, despite its proximity to the nation's largest concentration of nuclear reactors, has been denied access by the science ministry to a key computer simulation program that would allow it to prepare better for nuclear disaster.
The prefectural government made the request six months ago as part of efforts to craft a contingency plan amid public concern over the nuclear disaster in Fukushima Prefecture following the March 11 Great East Japan Earthquake.
Shiga Prefecture shares its northern border with Fukui Prefecture, which is home to 13 nuclear reactors.
The science ministry denied Shiga Prefecture access to its System for Prediction of Environmental Emergency Dose Information, or SPEEDI, on grounds that its use has been limited to prefectures hosting nuclear plants or related facilities and those within 10 kilometers from such installations.
Its border with Fukui Prefecture is 13 kilometers from the Tsuruga nuclear plant in Tsuruga operated by Japan Atomic Power Co.
Shiga was the first prefecture to attempt to predict the spread of radiation in a nuclear accident on the scale of the disaster at the Fukushima No. 1 nuclear power plant.
The ministry has declined to give an explicit answer to Shiga Prefecture's request.
"We will weigh (it), but we don't know when we can offer access," a ministry official said.
The SPEEDI is capable of mapping the spread of radiation within a 100-km radius in less than 20 minutes if information on radioactive materials, as well as weather conditions and topography data, is inputted.
The system also forecasts radiation levels in the atmosphere and the effects of radiation exposure.
The Shiga prefectural government set out in May to draw up an emergency evacuation scenario in the event of a nuclear accident in Fukui Prefecture.
It did so because residents of Fukushima Prefecture living 50 km from the crippled plant were forced to evacuate as radioactive materials dispersed in a belt-like wave due to wind activity and features in the terrain.
On four occasions since June, Shiga Governor Yukiko Kada and senior prefectural officials have visited the Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Economy, Trade and Industry, which is in charge of the nation's nuclear policy, to request a radiation prediction map.
But an official at the science ministry's Nuclear Safety Division said Fukui authorities would have to be consulted first before a decision is made on whether to allow Shiga Prefecture to use the SPEEDI system.
The ministry is still reluctant about meeting the request although it acknowledged that a proposal was made in October at a working group with the Nuclear Safety Commission of Japan, based in the Cabinet Office, that the radius for areas bracing for a possible nuclear accident be expanded to within 30 km, instead of the current 8-10 km.
In November, with no assistance from the central government, Shiga prefectural authorities mapped out how radioactive iodine would disperse in the event of an accident at the Mihama plant in Mihama, or the Oi plant in Oi, both in Fukui Prefecture and operated by Kansai Electric Power Co.
But the simulation was done by the computer system that is normally used to predict the spread of particles contributing to air pollution, and assumed that the scale of the nuclear accident was as serious as the one at Fukushima.
Once that was established, the simulation carved up the prefecture into three regions based on estimated thyroid gland exposure to radiation through inhalation if an individual spent eight hours outdoors and the rest indoors.
One region would require immediate evacuation due to radiation levels of 500 millisieverts or more. In another, residents would be required to remain inside concrete buildings due to radiation levels of between 100 millisieverts and 499 millisieverts. And finally, residents would be required to stay indoors due to radiation levels measuring between 50 and 99 millisieverts.
In the simulation involving the Mihama plant, 60 weather patterns observed last year were used.
Shiga Prefecture released only the results of its own areas as nearby prefectures did not agree to the disclosure.
But officials in Shiga Prefecture said the simulation map needs to be verified by nuclear experts because it was not based on the
dispersion of radioactive materials.
"We need a predicted radiation dispersion map produced by the SPEEDI to formulate an emergency evacuation plan," said an official at Shiga Prefecture's disaster management bureau.