As of 18 March 2011, 06:10 UTC (02:10 am Friday March 18 ET), the IAEA says that 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.  If fuel is no longer covered by water or temperatures reach a boiling point ~100 °C, fuel can become exposed and there is 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.

Unit 3

Concern about spent fuel storage conditions has led Japanese officials to attempt to drop water from helicopters (unsuccessful) and spray water from police water cannon trucks (unsuccesssful) and military fire trucks (successful, 30 tonnes) onto Unit 3 Reactor Building.

Unit 4

The IAEA reports that 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.

Units 5 and 6 Reactors

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

Units 5 and 6 Spent Fuel Pools

JAIF has reported rising temperatures of the SFPs at Units 5,6 since March 15.

NISA has reported increasing temperatures in the spent fuel ponds at Units 5 and 6 since 14 March. NISA also says that the emergency diesel generator at Unit 6 [the only one that survived the tsunami ?] is now powering water injection into the spent fuel pools at those Units.

Temperatures of SFPs at Units 4,5,6

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