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Re IC, I checked the NISA Sep update to IAEA again, pp II-82: "A little after 18:00 on March 11, possibly because DC power supply was recovered, the display lamps of return line and feeder line isolation valves of System A were lighted again to show the valves were closed. Because of this, valve-opening operation was performed at 18:18 on March 11; it was confirmed by station employees that vapor was generated from the exhaust port. However, closing operation of return line isolation valves of System A was performed at 18:25 on March 11 because it became impossible to confirm the vapor immediately after that.
After that, opening operation of return line isolation valves of System A was performed at 21:30 on March 11 to maintain the open state after steam generation was confirmed." The steam gives some indication that water was condensed. Alas, it did not suffice.

Suspicious of the IC performance, tepco tried an alternative via the core sprayer (CS), according to the same report: "Regarding water injection to reactors, in order to develop alternative water injection line via the core spray system(CS)from FP line, staff entered the reactor buildings in the dark, manually opened valves of CS, etc, then after the depressurization of reactor pressure (less than 0.69MPa gage), made the condition available for water injection.
At 17:30, March 11, the diesel-driven fire pump was confirmed to be in a workable condition. Since the indicated value of the supervisory instrumentation in the main control room was invisible, the staff entered into the reactor building and confirmed that the pressure gauge indicated 6.9MPa gage (20:07, March 11). After that, the water-level gauge was restored at 21:19 on the same day, confirming the indication of TAF+200mm.
At 01:48, March 12, staff confirmed that the diesel-driven fire pump which had been in operation for injecting water to the reactor stopped at some point, thus they carried and supplemented light oil manually, carried batteries kept in cooperative firms on the site for replacement, etc, but could not restart the operation." Note the pressure readings! Before 17:30 tepco managed to diminish rpv pressure to less than .69MPa. Within 2 hours and a half, the pressure climbed ten-fold. So the water injection attempt through the core sprayer did not help.

Consider while the fuel was melting in the reactor, guys were repeatedly sent into the building.

@lillymunster Good afternoon. Regarding the strontium-89: Having a half-life of 50 days means its radioactivity will decrease by half in roughly 50 days (statistically speaking), which means if you had a high release, you will be able to trace it for at least two years before it drops down to undetectable levels. Roughly speaking, an isotope with a half-life of 1 week can be traced for 3 or 4 months if the initial release is significant before it becomes undetectable. So, no wrong in that assumption back there.

@lillymunster , as I see it, the CS works only at low rpv pressures. As always, when tepco says they initiated an action or actuated a valve, it does not necessarily mean that it actually happened.

Europe-MultiCountries Nuclear Event Update. November 25.2011. The cause of the release of the I-131 is under investigation. "Might have emitted from Hungary". Pakistan has been cleared, saying that the release of I-131 is not possible unless there is a nuclear fuel failure. While the incident at Kanupp involved leakage of heavy water, which contains tritium and not Iodine-131. hisz.rsoe.hu