Borehole Nuclear Reactor

After some research on geothermal heat pumps, I realized that if you extract heat faster than the heat-conducting rate of the soil or rock allows the heat to move into the volume you have exhausted, the system will be tapped out. Heat can't radiate back towards your collectors fast enough. Now, this doesn't mean geothermal is unviable, it means each system has a maximum and if that is exceeded, it will not work as well. Also, in areas where summer air-conditioning needs equal winter heating needs, all is well. And in areas where air conditioning needs exceed heating needs, there is a similar problem: you are pumping heat into the ground faster than it can dissipate.

But in the American North, heat is the more precious commodity. This led me to ponder "recharging" heat in the earth with nuclear power. And my familiarity with deep holes in the petroleum industry led to my next idea:

After you run a nuclear power plant for a while, radiation will erode the reactor liners and concrete containment vessels. Eventual disposal or abandonment of all this material is expensive.

I propose lowering working fuel and control rods into the boreholes of either abandoned oil and gas wells, or drilling deep holes specifically for this proposed technology. Steam heat exchangers would be at the surface for electrical power generation. Or, for facilities such as government installations, colleges and universities, etc., the heat alone could be used to warm the buildings.

Eventually each reactor hole will be abandoned, using standard well-abandonment techniques. This involves heavy rubber and iron plugs topped with cement and should guarantee no contamination of groundwater. The heaviest-irradiated zones will be deep in the earth, in effect being "pre-disposed of." No further transportation of these deep abandoned materials will be required.

One advantage to this is it keeps operating core and waste nuclear materials far away from any terrorists. 10,000 feet of rock is a good deterrent to this sort of mischief.

UPDATE 5/1/09
A nuclear technician has pointed out to me that there's too much radioactive water in that l-o-n-g heat exchanger. I need a secondary heat exchanger. Or a liquid sodium design.