Japan Earthquake Update (18 March 2011, 12:25 UTC)
Japanese authorities have informed the IAEA that, prior to the earthquake of 12 March, the entire fuel core of reactor Unit 4 of the Fukushima Daiichi nuclear power plant had been unloaded from the reactor and placed in the spent fuel pond located in the reactor's building.
(confirmation qu'avant le séisme du 12 mars l'intégralité du combustible du réacteur 4 avait été placé dans la "piscine" de transfert, située dans l'enceinte de la centrale.)
Clarification
Contrary to several news reports, the IAEA to date has NOT received any notification from the Japanese authorities of people sickened by radiation contamination.
'Contrairement à certaines infos, l'IAEA n'a pas eu connaissance de la part des autorités japonaises de personnes malades à cause des radiations)
In the report of 17 March 01:15 UTC, the cases described were of people who were reported to have had radioactive contamination detected on them when they were monitored.
Japan Earthquake Update (18 March 2011, 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.
Addition of 12:45 UTC
Japanese authorities have assessed that the core damage at the Fukushima Daiichi 1 reactor unit caused by the loss of all cooling function has been rated as 5 on the INES scale.
This is an upgrade from a previous rating of 12 March as 4 on the INES scale, which was based on an abnormal rise of radioactive dose rate at the site boundary.
(En gros: les autorités japonaises confirment que le problème rencontré par le non refroidissement du réacteur 1 est passé de 4 à 5 sur l'échelle de risque internationale, suite à l'élévation des doses mesurées à la périphérie du site)
Further information on the ratings and the INES scale.
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:
| Unit 4 | |
| 13 March, 19:08 UTC: | 84 °C |
| Unit 5 | |
| 17 March, 03:00 UTC: | 64.2 °C |
| 17 March, 18:00 UTC: | 65.5 °C |
| Unit 6 | |
| 17 March, 03:00 UTC: | 62.5 °C |
| 17 March, 18:00 UTC: | 62.0 °C |
En gros: c'est plus chaud qu'avant...
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.
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