Well I’m wondering how you reached the number of 120 years, as numbers that I’ve seen (as part of my university course) quote 100-500 years of nuclear with current technology, and the potential for >10000 years with newer fast breeder reactor technology. Furthermore, newer deposits of uranium may become a possibility (such as the extraction of uranyl ions from seawater and/or seaweed), meaning that conventional light water reactors burning enriched uranium may be sufficient for ~1000 years. (Original source is Westinghouse Electric Company, BP, US Geological Survey and World Nuclear Association – https://docs.google.com/viewer?url=http%3A%2F%2Ffire.pppl.gov%2Fward_sustainable_soft06.ppt&docid=7eb7e84e6a2beaec8cb9f4ab4428b441&a=bi&pagenumber=16&w=800).
If you can provide a source for your estimate, I’ll be happy to look at it.
And just in case you were interested, I’m not interested in pursuing fission technologies, as fusion has greater potential as an energy source, but I see fission as a way to cut our CO2 emissions drastically without compromising energy production. Yes, waste can be extremely radioactive, but this issue can be reduced drastically without much worry and, more importantly, can be localised.
Are you considering fast reactors in those 120 years? Because then we’re not limited to burning U-235 in reactors, and suddenly all of the stockpiled plutonium, depleted uranium and spent fuel becomes a very useful resource.
Note that this has little to nothing to do with building reactors now, though, since reactors have a ~30 year operational life anyway and the main concern is actually reducing carbon emissions.
A few things: basically, using thorium is like a more effective way of using depleted uranium – a fertile material that produces good amounts of fissile material, but that does not mean it’s incapable of producing weapons grade material, nor does it mean it’s inherently safer.
The trait you mention, a reaction that slows, wasn’t a trait of some famous reactors (notably, Chernobyl), but modern reactors can be designed in such a way. Case in point, the AP1000 (from Westinghouse) uses more passive safety systems, the reaction itself is sustained by particular conditions (such as the presence of boron control rods and/or boric acid, variable moderating properties of water, etc.).
For instance, Fukushima never suffered a runaway reaction, but the main damage was caused by a loss of coolant flow (this heated the zircalloy cladding, causing the production of hydrogen gas and a subsequent explosion). The heat that was produced at this point wasn’t even from fission, but from radioactive products. This is the main issue in modern reactor designs, and has been addressed in the most recent designs (rather than relying on backup pumps that might fail, newer reactors can convect heat away from the fuel rods by natural convection, no need for intervention).
I’m all for safer reactors (I’ll probably end up working in one, after all), but I don’t see any reason that thorium fuel cycles wouldn’t suffer the exact same problems as uranium/MOX or any other fertile fuels would produce.
Honestly, I would prefer the use of fast reactors, running on a combination of separated (waste) plutonium, depleted uranium, thorium and any other higher actinides . The stockpile of ‘waste’ that can be reduced by this is enormous.
Shocker: the reason that efficiency is paramount with fossil fuel isn’t because better efficiency is better for everyone, it’s that it’s cheaper for the companies producing power. Nuclear reactors aren’t built to be efficient, because the fuel is relatively cheap. Comparatively, the cost of fossil fuel is much higher, which is why you see things like CCGT technology.
Don’t forget breeder/fast breeder reactors. They could burn depleted uranium, used fuel and separated plutonium. Only problem is the higher build costs than conventional LWRs… I dunno, maybe the RMWR will help.
