Higashidori: Very nearly SBO

Information released today by NISA indicates that the Higashidori Nuclear Power Station, owned and operated by Tohoku Electric Power Company, did in fact get very close to experiencing an actual Station Blackout event. Here from the narrative style data provided by NISA is a brief timeline of events at Higashidori following the April 7 earthquake off Miyagi Prefecture (which is assumed to be an aftershock from the March 11 Great East Japan Earthquake):

23:32 on April 7th: Earthquake off the coast of Japan. Many power lines go out, and blackouts occur in many places at this time or shortly thereafter. Higashidori, which had been shut down since the first earthquake March 11th, experienced a LOOP (Loss Of Offsite Power) event and was forced to use EDG power. However, two of the three diesels were out of service for inspection and unavailable. The one remaining EDG was started and placed on line to power the plant.

03:30 April 8th: One offsite power source is recovered. This was a four hour period in which the plant relied on a single EDG for power.

13:55 April 8th: The running diesel is found to be leaking oil. This diesel is shut down at 14:06.

14:59 April 8th: The other two offsite power lines are again available. There had thus been a period of about one hour in which the plant relied on a single offsite power line for power.

07:00 April 9th: The diesel that had been in service, unit B, was again ready for operation. This made a period of about 17 hours during which the plant had no EDG capability at all.

Previously, I had indicated in another post that there were data beginning to come out of Japan that might tend to indicate that the general level of attention to EDG capability / reliability and also attention to the threat of SBO situations might be lacking, and this chain of events just revealed for Higashidori... which is operated by a totally different company... is one more indication along those lines.

To be clear, this situation was THEORETICALLY dangerous and there are no reports of abnormalities at Higashidori either from the reactor plant or spent fuel aspects.

I for one would hope that some of these "periodic inspections" at various Japanese plants would immediately be ended, and the diesels reassembled, tested and made ready for auto-start.

10:00 PM Eastern Saturday 4/9
ATOMIC POWER REVIEW