At 9:48am on 17 March Japanese helicopters began aerial water spraying in an effort to cool the spent fuel pool at reactors 3 of the Fukushima Daiichi nuclear power station.
High-pressure water cannons have also been sent to pump water in from the ground, however heavy debris from the March 14 explosion at reactor 3 needs to be removed before operations can get underway.
The temperatures of the spent fuel pools at reactors 4, 5 and 6 have been rising following the tsunami and earthquake that hit the northeastern coast of Japan on 11 March. The International Atomic Energy Agency says “The concern about the spent fuel pools at Fukushima Daiichi is that sources of power to cool the pools may have been compromised.”
On Wednesday (16 March) the temperature of the spent fuel pool at reactor 4 was 84°C. Temperatures of pools at reactor 5 and 6 were 62.7°C and 60.0°C, respectively, and appeared to be rising, according to data from the IAEA. Typical temperatures of the spent fuel pools are about 30°C.
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 water-spraying operation was planned for Wednesday, but was postponed because of high radiation levels at the plant.
Plant operator Tokyo Electric Power Company has released the following information about the radiation levels at the plant. It said that levels of 400mSv/h were measured at the inland side of the unit 3 reactor building and 100mSv/h at the inland side of the unit 4 reactor building at approximately 10:00am on 17 March.
Tepco workers are continuing efforts to restore offsite power to the plant.
FilesReactor-by-reactor, system-by-system summary from JAIF on 18 March