4 ms·

Ignoring the hazardous nature of something like this - how economically viable would this be today? Let's say over a 10-year span driving 10,000 miles/year.. ho

by rjv 14y ago

Ignoring the hazardous nature of something like this - how economically viable would this be today? Let's say over a 10-year span driving 10,000 miles/year.. how much would I spend on gasoline at 30 mi/gal vs. plutonium?

mseebach 14y ago
This thread suggests that a small power plant at 1.5 GW takes about 1500 kg of uranium a year[1]. That's 13,140 GWh, or 0.114 kg uranium pr. GWh. A regular car motor produces up to 90kW[2]. 10000 miles at 40 mph average is 250 hours, or 2,500 hours over the 10 year. It's low speed, so let's assume the engine runs at half the rated output on average, 45kW, for a total of 112 GWh or 12.8 kg uranium. The classroom stuff is $90/kg[3], or $1,152 total fuel costs for ten years. 1: http://www.physicsforums.com/showthread.php?t=360052 http://www.physicsforums.com/showthread.php?t=360052 2: http://en.wikipedia.org/wiki/Nissan_SR_engine http://en.wikipedia.org/wiki/Nissan_SR_engine 3: http://www.chemicool.com/elements/uranium.html http://www.chemicool.com/elements/uranium.html Edit: more importantly, though: nuclear reactors are very poor at variable power output, so they are a bad fit for cars. Perhaps long haul trucks.
- morsch 14y ago
  Of course, uranium prices would probably go up as the resource gets increasingly rare and would go down as resource production ramps up as a reaction to increasing demand. If I were to hazard a wild guess, the former would be dominant, ie. prices would go up.
- uvdiv 14y ago
  Appreciate the effort, but there's some huge errors there. The reactor you mention will fission 1,500 kg of one isotope, U-235 -- out of some ~50,000 kg of nuclear fuel (3-5% U-235, rest being useless U-238), and 300,000 kg of mined uranium (mostly U-238, most of which is thrown away in enriching from 0.7% to 3-5% U-235 fuel). OTOH, your classroom uranium cost is for natural uranium, 0.7% U-235. So you're underestimating cost by 2 orders of magnitude at least. Here's real numbers from the industry [1]. You use $90/kg. They say on the the order of $3,000 per kg of reactor-grade UO2, which is $60,000-$90,000 per kg of the U-235 isotope. On the flip side, you're greatly overestimating fuel usage (your assumptions are equivalent to about 6 mpg mileage), and you have a unit error where you accidentally multiplied by one thousand (45 kW * 2,500 hours = 112 MWh, not GWh!). So the figure is about 1/3,000x yours: about 5 grams U-235, or 100 grams reactor-grade fuel, or 1 kg of natural uranium. Costing on the order of $300. This doesn't apply to (imaginary) nuclear cars. With reactor-grade fuel, you need hundreds of tons of uranium, and hundreds of tons of moderator, to get a critical reaction. This won't fit into a car. The only way to approach a reactor this small is to use highly enriched fuel -- "weapons-grade", which is not sold at petrol stations. This is how they miniaturize reactors to fit in submarines and space satellites (like [2], not an RTG). If you did try to build a car like this, it be pathologically wasteful. The amount of HEU would need to be several kg or more, to have a critical reaction at all. But because a car uses so little power, you would burn less than 1% of it (several grams) over hundreds of thousands of miles. Extrapolating (using [3]) enrichment costs ($150/SWU from [1]), the fuel cost would be on the order of $300,000. And almost entirely wasted. [1] http://www.world-nuclear.org/info/inf02.html http://www.world-nuclear.org/info/inf02.html [2] http://www.etec.energy.gov/Operations/Major_Operations/SNAP_Overview.html http://www.etec.energy.gov/Operations/Major_Operations/SNAP_... [3] http://www.wise-uranium.org/nfcue.html http://www.wise-uranium.org/nfcue.html

by rjv 14y ago

mseebach 14y ago

This thread suggests that a small power plant at 1.5 GW takes about 1500 kg of uranium a year[1]. That's 13,140 GWh, or 0.114 kg uranium pr. GWh. A regular car motor produces up to 90kW[2]. 10000 miles at 40 mph average is 250 hours, or 2,500 hours over the 10 year. It's low speed, so let's assume the engine runs at half the rated output on average, 45kW, for a total of 112 GWh or 12.8 kg uranium. The classroom stuff is $90/kg[3], or $1,152 total fuel costs for ten years. 1: http://www.physicsforums.com/showthread.php?t=360052 http://www.physicsforums.com/showthread.php?t=360052 2: http://en.wikipedia.org/wiki/Nissan_SR_engine http://en.wikipedia.org/wiki/Nissan_SR_engine 3: http://www.chemicool.com/elements/uranium.html http://www.chemicool.com/elements/uranium.html Edit: more importantly, though: nuclear reactors are very poor at variable power output, so they are a bad fit for cars. Perhaps long haul trucks.

morsch 14y ago
Of course, uranium prices would probably go up as the resource gets increasingly rare and would go down as resource production ramps up as a reaction to increasing demand. If I were to hazard a wild guess, the former would be dominant, ie. prices would go up.
uvdiv 14y ago
Appreciate the effort, but there's some huge errors there. The reactor you mention will fission 1,500 kg of one isotope, U-235 -- out of some ~50,000 kg of nuclear fuel (3-5% U-235, rest being useless U-238), and 300,000 kg of mined uranium (mostly U-238, most of which is thrown away in enriching from 0.7% to 3-5% U-235 fuel). OTOH, your classroom uranium cost is for natural uranium, 0.7% U-235. So you're underestimating cost by 2 orders of magnitude at least. Here's real numbers from the industry [1]. You use $90/kg. They say on the the order of $3,000 per kg of reactor-grade UO2, which is $60,000-$90,000 per kg of the U-235 isotope. On the flip side, you're greatly overestimating fuel usage (your assumptions are equivalent to about 6 mpg mileage), and you have a unit error where you accidentally multiplied by one thousand (45 kW * 2,500 hours = 112 MWh, not GWh!). So the figure is about 1/3,000x yours: about 5 grams U-235, or 100 grams reactor-grade fuel, or 1 kg of natural uranium. Costing on the order of $300. This doesn't apply to (imaginary) nuclear cars. With reactor-grade fuel, you need hundreds of tons of uranium, and hundreds of tons of moderator, to get a critical reaction. This won't fit into a car. The only way to approach a reactor this small is to use highly enriched fuel -- "weapons-grade", which is not sold at petrol stations. This is how they miniaturize reactors to fit in submarines and space satellites (like [2], not an RTG). If you did try to build a car like this, it be pathologically wasteful. The amount of HEU would need to be several kg or more, to have a critical reaction at all. But because a car uses so little power, you would burn less than 1% of it (several grams) over hundreds of thousands of miles. Extrapolating (using [3]) enrichment costs ($150/SWU from [1]), the fuel cost would be on the order of $300,000. And almost entirely wasted. [1] http://www.world-nuclear.org/info/inf02.html http://www.world-nuclear.org/info/inf02.html [2] http://www.etec.energy.gov/Operations/Major_Operations/SNAP_Overview.html http://www.etec.energy.gov/Operations/Major_Operations/SNAP_... [3] http://www.wise-uranium.org/nfcue.html http://www.wise-uranium.org/nfcue.html