Friday, September 18, 2009

Proposal to Ding Nuclear Station

Ding is a large 4 unit nuclear station on the north shore of Lake Ontario. It was designed and mostly built in the 70's, and as such suffers from a very old seismic design basis. This is now proving to be rather useless when checking out modern equipment, which is seismically qualified to modern standards.

ding used a base seismic ground motion that could never exist in the real world. It was a combination of soil motions in California, and grossly amplified by erroneous assumptions. The ground motions in the upper stories of this extremely stiff building were calculated to be a factor of 10 over the base. No amplification has ever been observed in this type of structure, but it might be as high as 1.5.

ding needs to abandon the original assumptions, and go with modern experience data. As well, being Ontario, they should base their approach on peak ground velocity (PGV), rather than peak acceleration. As such, they are safe to take some of the worst assumptions from modern geology, and construct scenario earthquakes. Most likely an M6.5 under Hamilton, and a local M5.0 near the plant, along one of the nearby mega-thrust basement structures.

Even under these circumstances, we only get a PGV of 10 cm/s, on the rock, and perhaps 20 cm/s on the till foundation of the turbine hall. Since these are plainly non-damaging levels, I would propose a new standard for ding. That is, not to merely have the safety systems undamaged, like a Japanese plant, but to make the whole plant operational during the scenario earthquake.

Ontario faces a grave situation when the Hamilton fault finally lets go. Under current circumstances, all the nuclear plants are expected to shut down, since they are totally unprepared for earthquakes. Like Japan, they will have 'funny business', leaks, and exploding transformers. Like Japan, the plants may not turn on for months. Should this happen during a cloudy January, wind-still cold snap (with the coal plants dismantled), Ontario is buggered.

As well, it is a little-known secret that nuclear plants need the power of another nuclear plant (or giant coal plant) to start up. This is called a 'black start'. It is possible to harden ding, so that it stays up, and merely goes to 60% because of electrical grid disruptions. This is a much better social situation.

ding can achieve this by running a seismic margin assessment on the plant, using a screening level of pgv of 30-50 cm/s. As with all nuclear plants (like Japan), ding is immensely strong in some areas, and very weak in others. It is the weak areas that will fail and close the plant.

Once we acknowledge that earthquakes are possible in our area, then this becomes the major social issue. Perhaps that is why nobody will touch it, since it is so grave, and makes previous ice storms and blackouts look like a picnic. The concept of all our nuclear plants bundled up like a Japanese 'quake-hit' reactor is too horrible to contemplate.


Harbles said...

Who dis guy?

Harold Asmis said...

He just runs that site as a geotechnical community site.