This is very good news. From Japan’s Nuclear and Industrial Safety Agency:
“Emergency Diesel Generator (1 unit) for Unit 6 is operable and supplying electricity to Units 5 and 6. Water injection to the Spent Fuel Pool through MUWC is progressing. It is scheduled to inject water to RPV after the recovery of external power source.”
What this means is that the reactors’ cooling systems will be able to be reactivated and the temperature of the used fuel pools in reactors 5 and 6 reduced. I’ll keep an eye out for some news coverage of this – TEPCO will no doubt have much more to say at its next press conference.
These two units were in the process of refueling at the time of the earthquake and cannot be used to generate electricity. But they should become non-issues as work on the four other reactors continues.