Japanese Earthquake Update (18 March 10:15 UTC)
Japanese authorities have informed the IAEA that new INES ratings have been issued for some of the events relating to the nuclear emergency at the Fukushima Daiichi and Daini nuclear power plants.
Japanese authorities have assessed that the core damage at the Fukushima Daiichi 2 and 3 reactor units caused by loss of all cooling function has been rated as 5 on the INES scale.
Japanese authorities have assessed that the loss of cooling and water supplying functions in the spent fuel pool of the unit 4 reactor has been rated as 3.
Japanese authorities have assessed that the loss of cooling functions in the reactor units 1, 2 and 4 of the Fukushima Daini nuclear power plant has also been rated as 3. All reactor units at Fukushima Daini nuclear power plant are now in a cold shut down condition.
Japan Earthquake Update (18 March 2011, 06:10 UTC)
Temperature of Spent Fuel Pools at Fukushima Daiichi Nuclear Power Plant – UPDATED
Spent fuel removed from a nuclear reactor is highly radioactive and generates intense heat. Nuclear plant operators typically store this material in pools of water that cool the fuel and shield the 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.
Given the intense heat and radiation that spent fuel assemblies can generate, spent fuel pools must be constantly checked for water level and temperature. If fuel is no longer covered by water or temperatures reach a boiling point, fuel can become exposed and create a risk of radioactive release. The concern about the spent fuel pools at Fukushima Daiichi is that sources of power to cool the pools have been compromised.
Concern about spent fuel storage conditions has led Japanese officials to drop and spray water from helicopters and trucks onto Unit 3 at Fukushima Daiichi nuclear power plant (See earlier update).
Japan’s Nuclear and Industrial Safety Agency has reported increasing temperatures in the spent fuel ponds at Units 5 and 6 since 14 March. An emergency diesel generator at Unit 6 is now powering water injection into the ponds at those Units, according to NISA.
The IAEA can confirm the following new information regarding the temperatures of the spent nuclear fuel pools at Units 4, 5 and 6 at Fukushima Daiichi nuclear power plant:
13 March, 19:08 UTC: 84 °C
17 March, 03:00 UTC: 64.2 °C
17 March, 18:00 UTC: 65.5 °C
17 March, 03:00 UTC: 62.5 °C
17 March, 18:00 UTC: 62.0 °C
The IAEA is continuing to seek further information about the water levels, temperature and condition of all spent fuel pool facilities at the Fukushima Daiichi nuclear power plant.
Japan Earthquake Update (17 March 2011, 16:55 UTC) – CLARIFIED
Japanese authorities have informed the IAEA that engineers were able have begun to lay an external grid power line cable to Unit 2. The operation was completed at 08:30 UTC. 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.
The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.
IAEA Briefing on Fukushima Nuclear Emergency (17 March 2011, 14:00 UTC)
At the IAEA headquarters in Vienna, Graham Andrew, Special Adviser to the IAEA Director General on Scientific and Technical Affairs, briefed both Member States and the media on the current status of nuclear safety in Japan.
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.
We are now receiving dose rate information from 47 Japanese cities regularly. This is a positive development. In Tokyo, there has been no significant change in radiation levels since yesterday. They remain well below levels which are dangerous to human health.
As far as on-site radiation levels at the Fukushima Daiichi and Daini nuclear power plants are concerned, we have received no new information since the last report.
In some locations at around 30 km from the Fukushima plant, the dose rates rose significantly in the last 24 hours (in one location from 80 to 170 microsievert per hour and in another from 26 to 95 microsievert per hour). But this was not the case at all locations at this distance from the plants.
Dose rates to the north-west of the nuclear power plants, were observed in the range 3 to 170 microsievert per hour, with the higher levels observed around 30 km from the plant.
Dose rates in other directions are in the 1 to 5 microsievert per hour range.
The Director General, who is now on his way to Japan, had another conversation with United Nations Secretary-General Ban Ki-Moon. The UN Secretary-General pledged all possible support for the Agency’s efforts.
The Director General also met the Executive Secretary of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), Tibor Toth, to discuss the possibility of the Agency gaining access to data collected by CTBTO radionuclide monitoring stations.
A written request has been made to CTBTO. We believe the additional data and information could assist the Agency in our assessment of the evolving situation in Japan.
A specialist from the World Meteorological Organization (WMO) joined our team in the Incident and Emergency Centre earlier this week, providing expert advice on the possible trajectories of winds from the area of the power plants.
Japan Earthquake Update (17 March 2011, 11:05 UTC)
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.
According to the press release, the droppings took place between 00:48 UTC and 01:00 UTC.