Update # 36: July 22, 2011
A new problem at the plant on Friday with two of three main power lines out.
The first report at 11:42 says there was a power surge on the two lines which tripper a circuit breaker.
(Much is being made in the press of the statement that no "major" change is seen in radiation levels, leaving one to wonder the magnitude of the change.)
External power supply cut at 2 Fukushima reactors
Tokyo Electric Power Company says part of the external power supply has been cut at the Fukushima Daiichi nuclear plant due to a problem in the transmission lines.
TEPCO said on Friday that a current breaker was tripped by a sudden surge in the external power lines, cutting off electricity to the No. 3 and 4 reactors.
The operator was forced to suspend a system treating radioactive water. Another system cooling the No.3 reactor's spent fuel storage pool was also shut down.
TEPCO says the pool's temperature remains stable at around 30 degrees Celsius.
After the power outage, a building serving as the headquarters for the plant's stabilization switched to an emergency generator.
TEPCO said work to inject water and nitrogen into the reactors has not been affected, as electricity is being supplied from other power sources.
It said radiation levels around the plant show no major change, and claimed there was little risk of a leak occurring.
TEPCO is working to restore external power, as it tries to find out what caused the problem."
Friday, July 22, 2011 11:42 +0900 (JST)
The second report approximately 9 hours later says the cooling for Unit 3 SFP was cut for 5 hours and again uses the phrasing "no major change" in the SPF temperature. It also says there was no radiation leakage. Oddly, though back-up power systems were in place, they did not automatically switch on as they were "not available". Whether that means they haven't been installed or they failed, we are left to speculate.
TEPCO probes Fukushima blackout
Tokyo Electric Power Company is investigating the cause of a sudden power failure at the Fukushima Daiichi nuclear plant. The blackout halted the cooling of a spent fuel pool for 5 hours….
The company says all facilities disabled by the incident have now been rebooted.
The utility says that although it has installed several external power sources, their automatic switchover functions were not available. The company says it will improve the systems.
A sudden surge in the external power supply is thought to be behind the failure. TEPCO says it is looking into the problem." Friday, July 22, 2011 20:23 +0900 (JST)
Not much in the press yet on this incident. The SFK blog has this to say:
#Fukushima I Nuke Plant: Power Is Off, TEPCO Doesn't Yet Know Why
"(UPDATE: OK It's back on again, but TEPCO still doesn't know what happened, according to their tweet at about 1:10PM their time on July 22. Looks like two power lines out of three that feed the plant went off. The contaminated water treatment system is still down.)
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The contaminated water treatment system, which stopped on July 21 (again) when a worker shut off the water gauge of the tank that stores the treated water (what a strange design, shutting off the water gauge shuts down the entire system..), continues to stop because power is off at the plant.
According to NHK Japanese (9:16AM JST 7/22/2011) and Yomiuri Shinbun (11:05AM JST 7/22/2011):
* Power to Reactor 3 and 4 was interrupted at about 7:10AM, due to the sudden power surge that tripped the circuit breaker at the temporary transformer. The cause for the sudden power surge is unknown.
* The cooling of the Spent Fuel Pool of Reactor 3 has stopped. No discernible change in the pool water temperature so far (30 degrees Celsius).
* Monitoring instruments for the reactor pressure are down.
* The headquarter building at Fukushima I Nuke Plant is operating on a backup generator.
* The cooling of the reactors and nitrogen gas injection continue uninterrupted, using the other power line."
I'll report more as this story develops.