The latest stoppage information from the tweet of a journalist who still regularly attend TEPCO's press conferences:
Email notification from TEPCO: "The water treatment system at Fukushima I Nuclear Power Plant resumed operation at 9:40AM on July 24 but an alarm sounded at about 12PM, and the system has shut down automatically."
From the tweet of an anonymous worker at Fukushima I Nuke Plant:
The clogged-up pipes are at AREVA's system.
But during the July 24 morning press conference that I watched, TEPCO was rather vague about where the location of the clogged pipes:
(When asked about the location of the pipes clogged with sludge,) the section is after the oil separation unit.
Well, the oil separation unit by Toshiba is the first process which the contaminated water goes through, and that doesn't say much. The clogged part could be Kurion's system, or AREVA's system. Or it could be even at the water desalination unit by Hitachi, which seems to be having its own problem, according to NHK:
The desalination unit stopped on July 24 for about 7 hours. TEPCO switched to the backup unit and continued desalination.
The desalination unit that uses reverse osmosis needs the treated water to have a certain, low enough level of radioactive materials to function properly.
Minor details, but also at the July 24 TEPCO press conference, the amount of water being injected into the Reactor Pressure Vessels (Reactor 1, 2, and 3) fluctuates for unknown reasons. Responding to a female reporter from NHK who asked about the fluctuation in the amount of water into the RPV (did you know it fluctuated? I didn't), TEPCO answered:
Yes, it does fluctuate, and no we don't know the reason why, but we monitor the digital display at the pump and adjust the water flow accordingly. The alarm is set to go off when the amount of water being injected goes too low. In case of Reactor 1, it is set at 2.5 tonnes/hour.
I just have an unfounded, unscientific feeling that all these small details add up someday to cause a one big, unexpected something. Don't ask me what it is.