Immediately following the earthquake and tsunami residents within 20 kilometers (km) (12. 4 miles) of Fukushima Dai-ichi were evacuated and those between 20 and 30 km (12.4 to 18.6 miles) were advised to remain in their homes as shelter or voluntarily evacuate. Subsequently, the Japanese government considered extending the evacuation zone to 30 km but ended up establishing a 20 milli-Sievert per year (mSv/y) or 2 rem/y dose limit for establishing which areas would be evacuated.
Also notably, shortly after the Fukushima accident began to unfold the US NRC was so concerned regarding how the accident might progress that it recommended that U.S. citizens stay at least 50 miles away. Some criticized the US NRC Chairman for this action. Given the uncertainties at the time the decision was made, and the fact that the Japanese mandatory evacuation standard, 20 mSv/y, ultimately impacted people out to about 75 km (46.5 miles), we believe the US NRC action was appropriate.
Based on Japanese census data, we estimate that before evacuation there were 69,000 people within 20 km (12.4 miles), 160,000 within 30 km (18.6 miles), and 2 million within 80 km (50 miles) of the Fukushima Dai-ichi reactor station.
Worldwide there are 135 reactor sites that have a greater number of people residing within 30 km of the reactor station than were residing within 30 km of Fukushima Dai-ichi; including 21 reactor stations with more than one million people within 30 km.Topping the list is the 125 MWe Karachi Nuclear Power Plant (KANUPP) in Pakistan, which has 8.3 million people within 30 km of the reactor. Two reactor stations on Taiwan—Kuosheng (2 operational reactors) and Chin Shan (2 operational reactors) have 5.5 million and 4.7 million people, respectively, living within 30 km; two adjacent stations in South Korea—Kori and Shin-Kori (5 operational reactors, 3 under construction and 2 planned) and two on the Chinese mainland— Guangdong/Daya Bay (2 operational reactors) and Ling’ao (4 operational reactors) have more than 3 million people within 30 km. A severe nuclear accident at any one of these stations could have devastating consequences for the entire country. Figure 1 displays a histogram of populations within 30 km of a reactor, worldwide.
Which reactors are located in areas that are in areas of high risk to earthquakes and tsunamis?
In a database maintained at NRDC, we have recorded the coordinates for 442 operational reactors in 31 countries, the majority of which are in North America and Western Europe. The geographic distribution of reactors worldwide may be analyzed with respect to two natural hazards that contributed to the accident at Japan’s Fukushima Dai-ichi nuclear power plant: seismic and tsunami risks.
Seismic hazard data was obtained from the Global Seismic Hazard Assessment Program (GSHAP), a demonstration program launched in 1992 by the International Lithosphere Program with the support of the International Council of Scientific Unions, and endorsed as a demonstration program in the framework of the United Nations International Decade for Natural Disaster Reduction. The GSHAP data consists of gridded seismicity hazard values in 0.1 decimal degree intervals in latitude and longitude. These seismicity hazard values are given in units of Peak Acceleration (m/s2) with 10% Probability of Exceedance in 50 Years. In these units, 0.0 to 0.8 are classified as a “Low Hazard;” 0.8 to 2.4 as a “Moderate Hazard;” 2.4 to 4.0 as a “High Hazard;” and greater than 4.0 as a 20 “Very High Hazard.” Figure 2 charts the number of operational reactors located in the given seismic hazard zones.
The 12 operational nuclear reactors within very high seismic hazard areas are listed in Table 3, and are located in Japan and Taiwan, including all of Taiwan’s six operating reactors.
In May of 2011 Japanese Prime Minister Naoto Kan requested that the Hamaoka Nuclear Power Plant be shut down, due to predictions that an earthquake of magnitude 8.0 or higher has an 87% likelihood of occurring in the area of the plant within the next 30 years. The plant remains shut and the reactors may begin decommissioning, pending the outcome of lawsuits. The three nuclear reactors at the Onagawa Nuclear Power Plant remain in cold shutdown following the March 11th earthquake and tsunami.
In addition to the six operating nuclear reactors in Taiwan located in a very high seismic hazard area, two additional reactors are under construction at Lungmen: Lungmen Unit 1 is expected to begin commercial operation at the end of 2011.
Of the 36 operating nuclear reactors in the high seismic risk category, 29 are in Japan, 4 in the United States and one each in Armenia, Iran (Bushehr) and Slovenia (Krško). The 67 operating nuclear reactors in the medium seismic risk area include 15 in Japan, 10 in 21 France, 5 in South Korea, and 5 in the United States.
The degree to which an earthquake will damage a nuclear reactor depends not only on the magnitude of the earthquake, but also on the reactor’s seismic design basis. We note that the reactors at Fukushima Dai-ichi appear to have withstood the March 11th earthquake, but the damage from the earthquake to the electric grid contributed to causing the station blackout conditions.
A world database of tsunami events is maintained by the US National Oceanic and Atmospheric Administration (NOAA) National Geophysical Data Center (NGDC). The majority of tsunami events for wave heights greater than 10 meters have occurred in: Indonesia, the United States, Japan, Tonga (an archipelago in the South Pacific Ocean) and in the Russian Far East regions.
With respect to earthquake and tsunami hazards, and large nearby populations, Taiwan’s six reactors represent outliers in terms of high risks and consequences from a nuclear reactor accident.
Thomas B. Cochran, Ph.D. Consultant Senior Scientists, Nuclear Program and Matthew G. McKinzie, Ph.D. Senior Scientist Natural Resources Defense Council, Inc.
P.S. This post is an excerpt from a longer paper “Global Implications of the Fukushima Disaster for Nuclear Power”