Tuesday, July 20, 2010

Ontario Earthquake produces first nuclear plant free-field record

The strong ground motions are in. They are in two big reports that I don't intend to read.

But we have the Darlington seismometer records! DRWO PGV was 0.28(E) 0.37(N) and 0.14(Z component).

I had surmised at an earlier date that the turbines could trip at 1 mm/sec free-field, but most likely at 5 mm/s. Nevertheless, this is a historic first for any nuclear plant east of the Rockies! They may have even triggered the internal accelerometer system, which would be a big double first! (I'll believe it when I see it). Pickering did have an acceleration recording, but no free-field.

From my indications, I think Darlington will show exactly as Pickering, which is a factor of 2 amplification in the upper stories in terms of velocity. The standard seismic design analysis produces a factor of over 10 in acceleration! That adds billions of dollars to the cost of construction, but lots of jobs to seismic people.

Experience data never shows an upper amplification of more than 2, more like 1.5. Combine this huge amplification with huge accelerations recorded by close high-frequency accelerations, and you have Big Shit! The standard review level earthquake is 30% g, and you can imagine 3 g accelerations at the top in design!

This is one reason why we'll never build a nuclear plant in Canada. It can be argued that our hard rock produces much higher peak accelerations (but piddly peak velocities).

So, if Darlington produces a record, and we convert it to velocity, and we correlate it with the free-field, it will be awesome!

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