Saturday, April 2, 2011

Ontario Nuclear Disaster Scenario

I have written about the Great Toronto Earthquake, and this adds the nuclear component.  I have reason to believe that the Hamilton Fault produces a large M6.5 every 500 years.  This is supported by the simple earthquake frequency plot, and by the extensive geophysics we did in the lake, which has been subsequently ignored by 3 mega-projects.  The lake sediments are rolled below a recent horizon, so there is no 'time history' record.  Should there ever be a study, I would look at varved deposits on the eastern end of the lake, where I suspect the huge lake seiche rolls up.

So, we start with the earthquake M6.5 to 7.0, rupturing the whole 30 km of the fault.  The lake is over the hanging wall, and there is movement upward of 20 cm.  This fault does not have the shear walls of New Madrid or Arkansas, so it must have a strike-slip component, with directivity towards Toronto.  Ground motion at the rupture is 40 cm/s on the broken rock of the hanging wall, and up to 100 cm/s on the soft sediments of Burlington Bay.  The footwall, to the NW should be limited to 10 cm/s.

Although people worry about the nuclear plants, it should be noted that at this point, the nuclear plant is the least of their worries.  All power and natural gas is out, and this could be in January.  Most back-up generators have been knocked off their foundations.  All housing on the soft sediments is destroyed.  Condo towers on the lake are tilting.

The moment the power goes out, all the nuclear plants have their turbines trip.  My biggest wish is that Darlington can go to 60% and keep a reactor running, but I doubt it.  As we know from the Big Blackout, nuclear power plants do not do well when the main power is knocked out.  Pickering had a terrible time, and so they put in a big backup power plant.  But this was designed just for a standard blackout with no seismic considerations.  They used footings on unstable soil.  We can expect this to be destroyed.  Pickering B backup generators have not been seismically reviewed, and we know from the blackout that nobody relies on them.

With all power out, Pickering now depends on water injection and thermo-convection to cool the nuclear fuel.  Although the fission is shut down, we know from Japan that the short-lived isotopes keep the fuel hot for weeks.  Here's where our 3 m seiche comes in.  Pickering has a golf-ball tower for emergency injection, but that's just for 1 reactor, there's not much water in it.  For anything more, they rely on lake water and pumps which need the back-up generators.  Pickering draws its water up a ditch into the lake.  This ditch is chock-full of loose silt.  The only reason it stays clear is because of the water the plant draws in.  A lot of silt goes into the pumps every day.

Our seiche rips that silt into a giant mud pie.  There is no water to draw, even if they had the power for the pumps.  I don't think thermo-syphoning is enough, and the fuel heats up.  At that point, the boiling water will not allow flow through the fuel channels.  The fuel elements and pressure tubes start to melt.  I hope by this time the calandria is filled with light water and poison so that the fission is stopped, but some pressure tubes will rupture, as they have before, and melted fuel drops into the calandria.  The vacuum building is overwhelmed, and there will be venting of radioactive iodine.  Firetrucks will attempt to get there through the debris, but I think the water mains will be shattered since that whole place is swamp.  Within a few days, the silt should settle down and they can get water.  There will be no power for a week, unless Darlington can stay up.

Remember, this is science fiction based on hard facts and my personal experience.  The odds of this happening are as remote as an M9 off Japan!  

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