h a l f b a k e r yA few slices short of a loaf.
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'Defense in depth' backup systems to keep nuclear reactors and fuel storage pools cool seem to depend entirely on cooling pumps driven by electric motors. Electricity is to be supplied as follows; by the station's turbines, from the grid, by diesel generators and by batteries.
Electric supply lines,
motors, control systems and generators are all easily damaged by seawater. Diesels on the other hand are not, as long as air intakes, exhaust and fuel supplies are placed high enough.
If just one backup used pumps driven directly by diesel engines, by shaft, belt or chain, wouldn't this add considerably to the overall safety?
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Normally I'd just say no: the first thing I "noticed" was that making things electric makes for a much more versatile system and avoids the silliness of using a power source that pollutes more and is more prone to failure. |
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However in this case I think that making the pumps optionally operable by another power source makes sense. |
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[ ] I don't think it should be a full time thing. |
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Electrical power can be just as robust as a mechanical link, and far more practical. In Japan, the fuel tanks of the diesel powered generators were destroyed by the tsunami, as the generators were foolishly placed on the ocean side of the plant and the wave was four feet higher than designed for. And with a direct mechanical link, getting the pumps running again would not have been as simple as bringing in another line. |
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I don't think that the problems here can be isolated to "power failure". I do like your idea for a robust system of direct redundancy. |
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How about requiring that all reactors are built over a 400ft
water-filled shaft, into which the fuel rods can be dropped if
things become embarrassing? I presume that a large enough
body of water would keep things cool convectively. |
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seems like a good idea. however that shaft would have to be able to bear the pressure of the reactor which would make it very expensive. |
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I don't follow - why would it have to take the pressure of the
reactor? |
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[MB] you really think that no-one would succumb to the temptation to use the 400 foot hole as a convenient place to chuck all kinds of inconvenient mid to low level waste? (see: Dounreay shaft) |
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And that would be bad because? |
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[Max] - why "over" said shaft? How about "in" - such that if something really bad happens to the point where there's nobody left running the thing, it can just stay there? |
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anything in the same chamber as the rods is pressurized when the reactor is in operation |
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No “because” because that kind of thing defines “bad”? |
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The hole in the ground disposal method is sort of automatic with the China Syndrome--melted fuel burning into the Earth until it reaches the water table. |
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Dropping just the fuel rods into a pit would practically guarantee a meltdown. You'd want to drop the entire core, moderators and all, and hope that nothing broke when it hit the bottom. |
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My suggestion would be to design the cooling system so that it can cope with a scrammed reactor purely via convection, with no need for pumps at all. |
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//with no need for pumps at all// |
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The design flaw of these GE reactors is they are not fail safe. |
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