Japanese authorities have informed the IAEA that the explosion at Unit 1 reactor at the Fukushima Daiichi plant occurred outside the primary containment vessel (PCV), not inside. The plant operator, Tokyo Electric Power Company (TEPCO), has confirmed that the integrity of the primary containment vessel remains intact.
As a countermeasure to limit damage to the reactor core, TEPCO proposed that sea water mixed with boron be injected into the primary containment vessel. This measure was approved by Japan's Nuclear and Industrial Safety Agency (NISA) and the injection procedure began at 20:20 local Japan time.
Japan has reported that four workers at Fukushima Daiichi were injured by the explosion.
NISA have confirmed the presence of caesium-137 and iodine-131 in the vicinity of Fukushima Daiichi Unit 1. NISA reported an initial increase in levels of radioactivity around the plant earlier today, but these levels have been observed to lessen in recent hours.
Containment remains intact at Fukushima Daiichi Units 1, 2 and 3.
Evacuations around both affected nuclear plants have begun. In the 20-kilometre radius around Fukushima Daiichi an estimated 170 000 people have been evacuated. In the 10-kilometre radius around Fukushima Daini an estimated 30 000 people have been evacuated. Full evacuation measures have not been completed.
The Japanese authorities have classified the event at Fukushima Daiichi Unit 1 as a level 4 "Accident with Local Consequences" on the International Nuclear and Radiological Event Scale (INES). The INES scale is used to promptly and consistently communicate to the public the safety significance of events associated with sources of radiation. The scale runs from 0 (deviation) to 7 (major accident).
Japan has also confirmed the safety of all its nuclear research reactors.
The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.
IAEA Director General Yukiya Amano provided a video statement on the aftermath of the earthquake and tsunami that struck Japan. Director General Amano expressed his sincerest condolences for the lives and homes lost, and said: "My heart goes out to the people of my home country as they rise to the challenge of this immense tragedy."
Director General Amano notes the current effort to prevent further damage to Unit 1 reactor at the Fukushima Daiichi nuclear power plant.
In response to the situation, Director General Amano also explained the IAEA's dual role to use emergency communication channels to exchange verified, official information between Japan and other IAEA Member States, as well as to coordinate the delivery of international assistance, should Japan or other affected countries request it.
The video statement can be accessed here.
Japan's Nuclear and Industrial Safety Agency (NISA) has informed the IAEA's Incident and Emergency Centre (IEC) that there has been an explosion at the Unit 1 reactor at the Fukushima Daiichi plant, and that they are assessing the condition of the reactor core.
The explosion was reported to NISA by the plant operator, Tokyo Electric Power Company (TEPCO), at 0730 CET. Further details were not immediately available.
Japanese authorities have extended the evacuation zone around the Fukushima Daiichi plant to a 20-kilometre radius from the previous 10 kilometres.
At the nearby Fukushima Daini nuclear power plant, the evacuation zone has been extended to a 10-kilometre radius from the previous three kilometres.
The authorities also say they are making preparations to distribute iodine to residents in the area of both the plants.
The IAEA has reiterated its offer of technical assistance to Japan, should the government request this. The IAEA continues to liaise with the Japanese authorities, and is in full response mode to monitor the situation closely around the clock as it evolves.
Japanese authorities have informed the IAEA's Incident and Emergency Centre (IEC) that, starting at 12 March 9:00 am local Japan time, they have started the preparation for the venting of the containment of the Unit 1 reactor at the Fukushima Daiichi plant through a controlled release of vapour. The operation is intended to lower pressure inside the reactor containment.
Evacuation of residents living within ten kilometres of the Fukushima Daiichi nuclear power plant is reported to be under way. An area with a radius of three kilometres around the plant had already been evacuated.
The evacuation of residents living within three kilometres of the Fukushima Daini nuclear power plant is also under way.
The IAEA's IEC continues to liaise with the Japanese authorities, and is in full response mode to monitor the situation closely around the clock as it evolves.