The Onagawa Nuclear Power Station (NPS) was "remarkably undamaged" by the Great East Japan Earthquake, an IAEA team of international experts has concluded, following a two-week mission to the plant.
Onagawa, facing the Pacific Ocean on Japan's northeast coast, was the nuclear power plant closest to the epicentre of the 11 March 2011 magnitude 9.0 earthquake that struck Japan and resulted in a devastating tsunami.
The plant experienced very high levels of ground shaking and some flooding from the tsunami that followed, but was able to shut down safely, IAEA reported.
“The structural elements of the NPS were remarkably undamaged given the magnitude of ground motion experienced and the duration and size of this great earthquake,” the team said in its draft report.
The 19-person team, with members from six countries, visited the three-unit Onagawa NPS to observe how structures, systems and components with significance to the safety responded to the earthquake and heavy shaking. They held discussions with the plant’s operators, and reviewed logbooks and repair reports documented after the earthquake.
The findings from the inspection will now be added to an IAEA database compiled by its International Seismic Safety Centre (ISSC) to provide knowledge for Member States about the impact of external hazards on nuclear power plants.
"The data we are collecting will make an important contribution to improving safety," said Sujit Samaddar, mission leader and head of the ISSC.