APR: your source for nuclear news and analysis since April 16, 2010

Tuesday, March 15, 2011

Fukushima Daiichi -- Initiating Event?

Our first post on the ongoing accident at Fukushima Daiichi was made at 6:00 AM Eastern time on Friday, March 11. It is now just after 9:00 AM on the following Tuesday and we believe that we can now answer a major question.

When this is all over and many books are written, one question will be of utmost importance to engineers, politicians, historians, citizens and school children -- and that is "What caused this accident?" To us, with a slightly better technical view, the question is better postulated at "What was the initiating event?"

We can now pretty safely say that the initiating event was the tsunami. We mean the onshore, destructive, abnormal rush of water... as separate from and distinct from the earthquake.

Nuclear plants shut down at exceedingly short notice or with absolutely no notice all the time. Not only does this happen at power plants around the Pacific and Far East every time an earthquake is detected, it happens at nuclear plants everywhere when a 'total load reject' happens such as if there is thunderstorm damage to the grid and electrical load being carried by the plant suddenly isn't there at all any more. We mentioned one very recent case (LaSalle) during our coverage of this event at Fukushima; so this in itself -- a turbine trip and reactor scram, whether due to earthquake or lightning strike -- does happen frequently.

One hour after the earthquake, however, the tsunami came on shore at Fukushima. This disabled the diesel generators, it is now being surmised, and it is now known that the vastly complicated electrical and electronic plant equipment was also damaged beyond previously credible possibilities. We can thus say that at this point, when normal core cooling, instrumentation and control were lost or compromised that the accident sequence was initiated.

This is VERY important to realize as the press worldwide calls for the termination of all of the momentum that nuclear energy has right now.

ATOMIC POWER REVIEW Tuesday 3/15 9:15 AM

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