Concrete Pump with 58 Meter Boom Replenishes Water at Fukushima Unit 4 Pool

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.

Fukushima Accident Summary From World-Nuclear.org

When the data differ, the on-going summary defers provisionally to the Japanese regulator.

Here is an excerpt dealing with the apparent rupture of the suppression chamber of reactor 2 on March 15 after its cooling power failed on the 14th and its water in the torus boiled.

From the "Fukushima Accident 2011" at World-Nuclear.org, last updated today (here):

After the hydrogen explosion in unit 1, some radioactive caesium and iodine were detected in the vicinity of the plant, indicating fuel damage. This material had been released via the venting.  Further I-131 and Cs-137 and Cs-134 were apparently released during the following two weeks, particularly following the apparent rupture of suppression chamber of unit 2 on 15th. The caesium was at low levels (about two orders of magnitude less than the iodine). The hydrogen explosion in unit 4 involving the spent fuel pond on 15th apparently added to the airborne radionuclide releases.