IAEA releases bulletin on Japanese nuclear plants

IAEA reports on the Daiichi nuclear plants in Fukushima:

Mar 17, 2011

Japanese authorities have informed the IAEA that engineers have begun to lay an external grid power line cable to Unit 2. The operation was continuing as of 20:30 UTC, Tokyo Electric Power Company officials told the Nuclear and Industrial Safety Agency.

They plan to reconnect power to Unit 2 once the spraying of water on the Unit 3 reactor building is completed.

The spraying of water on the Unit 3 reactor building was temporarily stopped at 11:09 UTC (20:09 local time) of 17 March.

Mar 17, 2011

The situation at the Fukushima Daiichi nuclear power plants remains very serious, but there has been no significant worsening since yesterday.

The current situation at Units 1, 2 and 3, whose cores have suffered damage, appears to be relatively stable. Sea water is being injected into all three units using fire extinguishing hoses. Containment pressures are fluctuating.

Military helicopters carried out four water drops over Unit 3.

Unit 4 remains a major safety concern. No information is available on the level of water in the spent fuel pool. No water temperature indication from the Unit 4 spent fuel pool has been received since 14 March, when the temperature was 84 °C. No roof is in place.

The water levels in the reactor pressure vessels of Units 5 and 6 have been declining.

Mar 17, 2011

Based on a press release from the Japanese Chief Cabinet Secretary dated 17 March 2011 04:00 UTC, the IAEA can confirm that the Japanese military carried out four helicopter water droppings over the building of reactor unit 3 of the Fukushima Daiichi nuclear power plant.

Mar 16, 2011

Spent fuel that has been removed from a nuclear reactor generates intense heat and is typically stored in a water-filled spent fuel pool to cool it and provide protection from its radioactivity. Water in a spent fuel pool is continuously cooled to remove heat produced by spent fuel assemblies. According to IAEA experts, a typical spent fuel pool temperature is kept below 25 ˚C under normal operating conditions. The temperature of a spent fuel pool is maintained by constant cooling, which requires a constant power source.
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The IAEA can confirm the following information regarding the temperatures of the spent nuclear fuel pools at Units 4, 5 and 6 at Fukushima Daiichi nuclear power plant:

Unit 4: 16 March, 05:00 UTC: no data
Unit 5: 16 March, 05:00 UTC: 62.7 ˚C
Unit 6: 16 March, 05:00 UTC: 60.0 ˚C

Mar 15, 2011

Japanese authorities have informed the IAEA that the evacuation of the population from the 20-kilometre zone around Fukushima Daiichi has been successfully completed.

The Japanese authorities have also advised that people within a 30-km radius to take cover indoors. Iodine tablets have been distributed to evacuation centres but no decision has yet been taken on their administration.

Mar 14, 2011

Unit 1 is being powered by mobile power generators on site, and work continues to restore power to the plant. There is currently no power via off-site power supply or backup diesel generators being provided to the plant. Seawater and boron are being injected into the reactor vessel to cool the reactor. Due to the explosion on 12 March, the containment building has been lost.

Unit 2 is being powered by mobile power generators on site, and work continues to restore power to the plant. There is currently neither off-site power supply nor backup diesel generators providing power to the plant. The reactor core is being cooled through reactor core isolation cooling, a procedure used to remove heat from the core. The current reactor water level is lower than normal but remains steady. The containment building is intact at Unit 2.

Unit 3 does not have off-site power supply nor backup diesel generators providing power to the plant. As the high pressure injection system and other attempts to cool the reactor core have failed, injection of water and boron into the reactor vessel has commenced. Water levels inside the reactor vessel increased steadily for a certain amount of time but readings indicating the water level inside the pressure vessel are no longer showing an increase. The reason behind this is unknown at this point in time. To relieve pressure, venting of the containment started on 13 March at 9:20AM local Japan time. Planning is underway to reduce the concentration of hydrogen inside the containment building. The containment building is intact at Unit 3.