NRA to advise wider nuclear safety zones

Nuclear regulatory authorities on Wednesday released their first projections for the spread of radiation from nuclear reactors in the event

of severe accidents like the meltdowns at the Fukushima No. 1 power plant last year, and the results show that bigger evacuation zones may be

needed.

The amount of radiation released a week after a catastrophic accident at Tokyo Electric Power Co.'s Kashiwazaki-Kariwa plant in Niigata

Prefecture could reach the level where evacuation is recommended for people living as far as 40 km away, the Nuclear Regulation Authority

said.

The regulatory body conducted radiation simulations for 16 nuclear plants to provide references for regional governments to expand areas

subject to special preparations for nuclear disasters from the current distance of 10 km from facilities.

The Nuclear Regulation Authority plans to propose disaster-mitigation guidelines under which 30-km emergency zones would be set around

nuclear facilities, but the new estimates may prompt local governments to designate bigger areas. The new guidelines are to be compiled this

month based on lessons learned from the Fukushima disaster.

The NRA found that radiation levels could reach 100 millisieverts in Uonuma, Niigata Prefecture, about 40.2 km from the Kashiwazaki-Kariwa

plant, based on the assumption that all seven of its reactors suffer meltdowns.

Radiation doses could also reach 100 millisieverts in locations a little more than 30 km from Chubu Electric Power Co.'s Hamaoka plant in

Shizuoka Prefecture, Kansai Electric Power Co.'s Oi plant in Fukui Prefecture and Tepco's Fukushima No. 2 plant in Fukushima Prefecture. The

only commercial reactors currently operating are two units at the Oi plant.

The simulations were based on calculations of precipitation and wind velocity in each area throughout a year.

The NRA, however, noted that the simulations should be used only as a "guide" to likely trends of dispersal of radioactive substances because

they did not take into account geographical features around the plants or changes in wind direction.

NRA Commissioner Kunihiko Shimazaki said the results are "very important" in getting a basic idea of how far contamination can spread but

acknowledged the need to create simulations that also reflect land features so local governments can compile their evacuation plans in line

with real-life conditions.

The International Atomic Energy Agency calls for evacuations when effective doses exceed 100 millisieverts in the first seven days of an

emergency.

The NRA plans to introduce the idea of a "precautionary action zone" and "urgent protective action planning zone" in line with IAEA

standards.

People in the precautionary zone would be told to evacuate immediately after an accident. It is expected to cover a 5-km radius around

nuclear plants. People in the other type of zone, which is expected to cover a 30-km radius, would be told to prepare to get out, depending

on the situation.

Local governments are expected to define the actual scope of the zones by themselves, but officials have called for more details about the

simulations.

https://www.japantimes.co.jp/text/nn20121024x1.html