Fukushima Daiichi 11 March 2011. Accident sequence, radiological consequences. 5. ed.

On March 11, 2011, the worst earthquake since records began in Japan occurring off the east coast of the main Japanese island of Honshu. The quake and, above all, the resulting tsunami devastated large areas of eastern Japan and resulted in an enormous number of victims: By mid-2014, official statistics show that around 18,000 people had died, and more than 2,600 people were still missing as of March 2013. It is estimated that around one million buildings were destroyed or damaged. At the Fukushima Daiichi nuclear power plant site, the earthquake and tsunami caused the almost complete loss of electricity supply to four of the six reactor blocks. This led to the most serious reactor accident since Chernobyl. Particularly in the first few days of the accident, considerable quantities of radioactive material were released into the atmosphere. These massive releases led to extensive contamination of the surrounding area. Around 170,000 people were affected by evacuations or recommendations to leave their homes. The magnitude of the releases meant that the accident was classified at the highest level of the International Nuclear and Radiological Event Scale (INES 7). The Fukushima accident was and is the subject of various activities and projects of GRS. With its emergency centre, it evaluated available information from 11 March to the beginning of July 2011 and prepared more than 200 publicly available situation reports on behalf of the Federal Ministry for the Environment (BMU). Since mid-2011, GRS has been analysing the accident sequence in several projects funded by BMUB and the Federal Ministry of Economics and Technology and has been developing its own simulation calculations. Since 2012, it has also been participating as one of now ten expert organisations worldwide in an OECD/NEA research project in which the extent of core damage in reactors 1 to 3 is simulated (see Chapter 4). In addition to the project-related work, a so-called forwarding message with recommendations for further optimization of the safety of German nuclear power plants was prepared (see Chapter 8). The present fifth edition of this report provides an overview of the state of knowledge on the causes, sequence and consequences of the accident that had been achieved by the beginning of 2016. The changes compared to the previous edition relate primarily to the inclusion of more recent findings on the radiological consequences (see Chapter 5) - here especially on the status of investigations into health effects - and to the measures taken to cope with the consequences of the accident at the site (see Chapter 6), such as the treatment and storage of contaminated water and the ongoing investigations of the affected reactors.