Another earthquake and tsunami hit Fukushima last week. Here’s what you need to know.

By: Yukari Sekiguchi and Sharon Squassoni

On November 21, 2016 at 5:59 a.m., a 6.9-magnitude earthquake triggered a one-meter (39 inches) tsunami that hit the Fukushima Daiichi Nuclear Power Plant. About 6,000 residents reportedly evacuated as a result of the earthquake.

Only five years ago on March 11, 2011, the same power plant was struck by a record-breaking earthquake and tsunami, which resulted in a meltdown of the cores of three nuclear power reactors at the Fukushima Daiichi nuclear power plant and a massive clean-up effort.

1) What is the status of TEPCO’s nuclear power plants in Fukushima?

There are two nuclear power sites in Fukushima- Fukushima Daiichi and Daini. The Fukushima Daiichi site is undergoing decommissioning after the 2011 earthquake. The Daini site has 4 nuclear power reactors, all of which shut down safely after the 2011 earthquake, but which have not yet reopened. There is currently no fuel in those reactors. Instead, the fuel was placed in wet storage pools at the reactors. After this week’s earthquake hit the north east coast of Japan, TEPCO initially said that there were no irregularities at the Fukushima Daiichi nuclear power plant. According to the Nuclear Regulation Authority (NRA), however, around 6:10 a.m., the cooling systems for the spent nuclear fuel pool at the №3 reactor of the Fukushima Daini nuclear power plant, where 2,544 nuclear fuel rods are stored, shut down. TEPCO said the earthquake “shook” water in the cooling tanks temporarily, leading to a decline in levels and an automatic shutdown of the cooling systems. The system returned to operation after 90 minutes.

2) Did residents evacuate?

About 6,600 residents of Fukushima Prefecture, Miyagi Prefecture, and Iwate Prefecture reportedly evacuated because of the tsunami on November 21, 2016. According to the government of the Fukushima Prefecture, however, evacuation orders were issued to a total of 64,315 residents in Shinchi town, Soma city, Minamisoma city, Naraha town, Tomioka town, Hirono town, and Iwaki city. At 6:56 a.m., evacuation orders were issued to residents who live in coastal areas by Naraha town, where the Fukushima Daini nuclear power plant is located and which lies within the 20-km-radius “hot zone” around Fukushima Daiichi nuclear power plant. The warnings were lifted in the early afternoon.

3) What lessons can we draw from this most recent earthquake and tsunami for nuclear emergency preparedness?

Compared to 2011, there are new systems in place to alert the public and the utility that runs the nuclear power plants, TEPCO, is communicating with a new nuclear regulator, the NRA. Within an hour of the shutdown of cooling systems, TEPCO had informed the NRA and the NRA passed along that information through an emergency email system in which citizens voluntarily participate. It is unclear how many people the NRA reached with its emergency email system. It is likely that many people discovered what happened in Fukushima Daini through the media announcement at 7:40 am.

The November 21 earthquake and tsunami in particular demonstrated that Fukushima Daini’s cooling system for spent nuclear fuel pools remains vulnerable. After the Fukushima nuclear accident in 2011, the NRA promoted the dry storage of spent nuclear fuel in order to reduce risks, but only two nuclear power plants (Fukushima Daiichi and Tokai 2) have moved to dry storage in the years since. From this most recent seismic event, improving spent fuel storage should be a priority issue in Japan.

Photo Credit: Christopher Furlong/Getty Images