.17 March 1200 JST.
The storage pools for spent nuclear fuel are located in the top parts of the reactor buildings, so that fuel normally removed from the reactors can quickly be placed into the pool.
Diagram showing the location of the pool in each reactor
The pool in reactor building 4 has caught fire twice and it was originally thought that there was no water left in the pool. Today it was discovered that there was still water in the pool.
As you can see below, the pool in reactor building 3 appears to be gone -- scattered perhaps by the hydrogen explosion that destroyed the exterior building
The remnants of the reactor building 3 is on the left. Reactor building 4 is in the middle of the photo.
Reference photo of the plant, showing reactors 2, 3, and 4 (l to r). This was taken from an angle similar to that of the previous photo. Note that the reactor building 3 has now collapsed almost down to the level of the low buildings.
Another photo of the damaged reactor building 3
Satellite photo of the four reactors on 16 March
"Plutonium-uranium mixed oxide (MOX) fuel rods are placed in a storage pool at the No. 3 reactor of the Fukushima Daiichi nuclear power plant in Fukushima Prefecture, northern Japan, in this picture taken August 21, 2010. Operators of the earthquake-crippled nuclear plant in Japan again deployed military helicopters on March 17, 2011, in a bid to douse overheating reactors, as U.S. officials warned of the rising risk of a catastrophic radiation leak from spent fuel rods." REUTERS/Kyodo
It is obvious to me that the spent fuel pool in reactor building 3 has been destroyed.
An attempt was made this morning (JST) to dump sea water on reactor 3 using helicopters, but it appeared to be highly unsuccessful. The four dumps were made at fairly high altitude (1000 meters), and most of the water appeared to be taken away from the reactors by the wind. Each pool holds around 2000 tons of water. Each helicopter drops about 7.5 tons.
CNN is only showing video of the one drop that managed to get significant water on the reactor. Here is a more realistic video:
Reactor 3 is a priority because it uses a combination uranium and plutonium fuel (MOX fuel), and appears to be heavily damaged, producing large quantities of steam from the reactor. It is believed that this steam is escaping from the reactor vessel itself.
Groups of police officers are planning to use 11 riot water cannons this afternoon to shoot water through holes in the reactor 4 building in an attempt to cool the fuel rods in its pool.
TEPCO is bringing in a new power line so that pumps can be run, but acknowledged that the the existing cooling pumps have been ruined by sea water, and temporary pumps will be required. I would suspect that the lines to the reactors have been destroyed, and I don't think reactors 2 and 3 will hold water.
The Japan Nuclear Industrial Safety Agency reported in a press conference on NHK TV today that the pools in reactors 5 and 6 are now in trouble, and may have only a little water left. Pressures and temperatures are rising.
Reactors 1 and 2 are being cooled by sea water, according to the Defense Minister, but if that were true, I would expect to see some steam escaping.
It is just me or does the whole response seem rather amateurish, with little or no long term planning?