Presumably one like this:
Another news report here said a 70 meter version was being dispatched.
The Fukushima Daiichi Unit 4 used fuel pool has needed nearly 1300 cubic meters of water over 13 days from April 13-25, according to this update. That number is consistent with, but about 200 cubic meters lower than, the predicted boil-off rate for the period in question:
Unit 4 pond contains a total 1331 used assemblies (783 plus full fuel load of 548), giving it a heat load of about 3 MW thermal, according to France's IRSN, which in that case could lead to 115 cubic metres of water boiling off per day, or about one tenth of its volume. ...
The pond at unit 4 is the main focus of concern now. It needs continual top-up with water, but at the same time there is concern about the structural strength of the building, which has been weakened either by the earthquake or the hydrogen explosion. Some 195 m3 was added to the pond on 13 April, about 20% of its capacity, and another 140 m3 on 15 and also on 17 April, by concrete pump. Another 100 m3 went in on 20 April, then 200 m3 on 22nd, 140 m3 on 23rd, 165 m3 on 24th and 210 m3 on 25th. Temperature has been up to 90°C and water level 5 metres down. It is not clear whether the main water loss is from leakage or boiling. However, Tepco reports that analysis of radionuclides in water from the used fuel pool of unit 4 suggests that some of the fuel assemblies there may have been damaged, but the majority are intact.
