Evacuating the area within 31 kilometers of the Hamaoka nuclear power plant could take nearly two days, leaving many residents exposed to radiation if a nuclear accident were to occur there, a study showed.
Evacuating the area within 31 kilometers of the Hamaoka nuclear power plant could take nearly two days, leaving many residents exposed to radiation if a nuclear accident were to occur there, a study showed.
Based on an evacuation simulation involving an accident at the plant in Omaezaki, Shizuoka Prefecture, caused by the Nankai Trough mega-quake and tsunami, it would take between 32 and 46 hours for all 860,000 residents in the area to evacuate, prefectural officials said.
“It is highly likely that portions of residents will be exposed to radiation,” an official said.
It is the first time for a local government to conduct a full-scale evacuation simulation of a multiple disaster involving an earthquake and nuclear accident, the officials said.
The nuclear plant, operated by Chubu Electric Power Co., is believed to be located within the hypocentral area of the Nankai Trough mega-quake, which could affect 29 prefectures from the Kanto region to Okinawa.
The Nankai Trough is a roughly 4-km depression on the seabed that extends about 700 km from Suruga Bay off Shizuoka Prefecture to areas off eastern Kyushu.
Shizuoka Prefecture decided to map an evacuation plan for residents living within a 31-km radius from the plant. The population in the area is the second largest among areas of the same size surrounding nuclear plants across Japan.
In the prefecture’s simulation, the 860,000 residents try to leave in 280,000 cars--one for each household--when roads in coastal areas are wiped out by a tsunami.
The simulation considered 12 scenarios, including whether or not prefectural officials regulate traffic, and estimated the amount of time residents need to evacuate outside the area for each case.
The shortest-time scenario is 32 hours and 25 minutes, in which all 860,000 residents evacuate immediately after the disaster unfurls.
But this scenario would cause major traffic jams everywhere, and evacuees would be stuck in their cars for 30 hours and 45 minutes, the longest time among the 12 scenarios. Remaining in vehicles could pose a higher risk of radiation exposure than staying inside buildings.
The 50,000 residents living within a 5-km radius from the Hamaoka plant would need to promptly leave from the area in the case of a nuclear disaster. It could take them 24 hours and 15 minutes to flee outside the 31-km radius.
The longest of the 12 scenarios would take 46 hours and 15 minutes. In this case, the prefecture would instruct residents to stay at home or in other buildings when traffic jams are expected. The areas would be divided into small blocks, with each ordered to evacuate one by one to prevent traffic snarls.
Residents in this scenario would need to spend a maximum 7 hours and 55 minutes in their cars. Depending on the location of their homes, however, some residents would have to wait inside buildings for much longer than in cases in which they take off immediately.
The simulation did not take into account damage to roads caused by earthquake jolts nor the evacuation of hospital inpatients and elderly people who would be unable to evacuate on their own.
The amount of evacuation time could be even longer when these issues are taken into consideration, the prefectural officials said.
During the initial stage of the Fukushima nuclear disaster in March 2011, an explosion occurred at a reactor building 18 hours after the evacuation order was issued.
In May 2011, then Prime Minister Naoto Kan ordered Chubu Electric Power to suspend all reactors at the Hamaoka nuclear plant.