Update from MIT: About those Choppers dropping water

Just from watching the video, the water drops on Fukushima don’t appear to be adequate for the task.

CNN reports:

Helicopters made four passes in about a 20-minute span Thursday morning, dropping 7.5 tons of seawater each time on the reactor in order to cool its overheated fuel pool. Kitazawa said 11 special water cannon trucks, along with one from Tokyo’s police department, should arrive at some point Thursday to spray water at the No. 3 unit from the ground.

While Kitazawa said “the criteria has been satisfied,” other officials said they were still collecting to determine what effect, if any, the dumping of water had.

Just as an outside guess, one would think that if they were able to, water drops would be continuous. 4 passes suggests they stopped for a reason, and the most likely would be high radiation readings.  This seems more like a gesture for the video than a serious plan being executed.

UPDATE: as of 0730 EDT, CNN is reporting “over 30 tons of water dropped”, which means they only have the 4 runs so far, as
the buckets are reported hold about 7+ tons per gulp. Water cannons have been on and off, temporarily pushed back by radiation, particularly gamma rays from the fuel pool. The reactor most at risk currently, number 4, has a huge hole in the wall, but the roof more or less intact – so it’s not amenable to airborne water drops, but apparently so radioactive that the water cannons can only hit it sporadically.

Gamma rays, the primary issue for the firemen here, are highly energetic and almost impossible to stop without very thick shielding.

From MIT Nuclear Science Info Hub:

UPDATE AS OF 9:00 P.M. EDT, WEDNESDAY, MARCH 16:

Crews began aerial water spraying operations from helicopters to cool reactor 3 at Fukushima Daiichi shortly before 9 p.m. EDT on Wednesday, March 16. The operation was planned for the previous day, but was postponed because of high radiation levels at the plant. News sources said temperatures at reactor 3 were rising. Each helicopter is capable of releasing 7.5 tons of water.

Spokesmen for TEPCO and Japan’s regulatory agency, Nuclear and Industry Safety Agency, on March 17 Japan time refuted reports that there was a complete loss of cooling water in the used fuel pool at Fukushima Daiichi reactor 4.

The spokesmen said the situation at reactor 4 has changed little during the day today and water remained in the fuel pool.
(This statement is at variance with US NRC evaluations) However, both officials said that the reactor had not been inspected in recent hours.

“We can’t get inside to check, but we’ve been carefully watching the building’s environs, and there has not been any particular problem,” said TEPCO spokesman Hajime Motojuku.

No particular problem?