12 Mar (NucNet): Tokyo Electric Power Company (Tepco) has confirmed that it has successfully vented the containment of unit 1 at the Fukushima-Daiichi nuclear power plant in northern Japan.
Meanwhile, chief cabinet secretary Yukio Edano has told a press conference that there was an explosion at Fukushima-Daiichi at 15:36 local time, but he said it has not affected the reactor’s primary system or its containment.
Mr Edano said there was a hydrogen explosion in the space between the concrete container and the reactor’s primary system. However, the explosion did not damage the containment function or the reactor system, he added.
In a statement, Tepco said the venting of unit 1 had been successful and it was preparing to vent units 2 and 3, which also shut down automatically when the 8.9-magnitude earthquake hit yesterday.
The utility also confirmed that the national government had ordered an evacuation for residents within a 10 km radius of the plant’s periphery.
Tepco has not yet made any comment on the explosion at the plant, although confirmation of successful venting would appear to contradict media reports that the containment has been breached.
Venting is designed to reduce pressure in the containment. It is not yet known why the pressure increased.
Earlier, Tepco said the pressure in unit-1’s containment was 600 kilopascal (6 bar) and according to Japan’s Nuclear and Industrial Safety Agency (NISA) it could have increased to 840 kilopascal (8.4 bar) in the meantime. NISA said the design pressure for the unit’s containment is 400 kilopascal (4 bar).
>Related reports in the NucNet database (available to subscribers)
Japanese Safety Agency Reports ‘No Incidents So Far’ Following Quake (News in Brief No. 50, 11 March 2011)
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