Japan Earthquake Update (12 March 2011 2110 CET)

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 170000 people have been evacuated. In the 10-kilometre radius around Fukushima Daini an estimated 30000 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.