Temperature of Spent Fuel Pools at Fukushima Daiichi Nuclear Power Plant
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.
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 may have been compromised.
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:
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.
Director General Yukiya Amano announced the following today in Vienna:
"I plan to fly to Japan as soon as possible, hopefully tomorrow, to see the situation for myself and learn from our Japanese counterparts how best the IAEA can help. I will request that the Board of Governors meet upon my return to discuss the situation. My intention is that the first IAEA experts should leave for Japan as soon as possible."
On 15 March, Japan requested the IAEA for assistance in the areas of environmental monitoring and the effects of radiation on human health, asking for IAEA teams of experts to be sent to Japan to assist local experts.
Given the fast-changing situation in Japan, the Director General was unable to announce the itinerary for his trip. He expects to be in Japan for a short amount of time and then return to Vienna.
Japanese authorities have reported concerns about the condition of the spent nuclear fuel pool at Fukushima Daiichi Unit 3 and Unit 4. Japanese Defense Minister Toshimi Kitazawa announced Wednesday that Special Defence Forces helicopters planned to drop water onto Unit 3, and officials are also preparing to spray water into Unit 4 from ground positions, and possibly later into Unit 3. Some debris on the ground from the 14 March explosion at Unit 3 may need to be removed before the spraying can begin.
Japanese authorities have informed the IAEA that a fire in the reactor building of Unit 4 of the Fukushima Daiichi nuclear power plant was visually observed at 20:45 UTC of 15 March. As of 21:15 UTC of the same day, the fire could no longer be observed.
Fire of 14 March
As previously reported, at 23:54 UTC of 14 March a fire had occurred at Unit 4. The fire lasted around two hours and was confirmed to be extinguished at 02:00 UTC of 15 March.
Water Level in Unit 5
Japanese authorities have also informed the IAEA that at 12:00 UTC of 15 March the water level in Unit 5 had decreased to 201 cm above the top of the fuel. This was a 40 cm decrease since 07:00 UTC of 15 March. Officials at the plant were planning to use an operational diesel generator in Unit 6 to supply water to Unit 5.
The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.