Relax is right. You can't build tiny nuclear reactors because you need a minimum mass to surface ratio to rech criticality. Smaller reactors require more highly enriched fuels unless you are using some of the exotic trans Uranic isotopes.
Of course Thorium is fissionable but with a rather low thermal neutron fission cross section but not fissile because it has an extremely low fission cross which does solve the proliferation problem.
I am far less than alarmed by the possibility of someone making bombs out of spent reactor fuel. Waste grade Plutonium is theoretically fissile. However; the high concentration of Pu-238 isotope makes it significantly radioactive and produces a lot of heat. The moderate concentration of Pu-240 isotope undergoes spontaneous fission, emitting neutrons that then fission the Pu-239. The result is significant energy production before a bomb can reach criticality making it really difficult to get detonation.
Screw the nuclear car.
Build nuclear power reactors to displace coal and natural gas generation. Then use the natural gas and coal to make synthetic fuels to power more conventional cars until battery technology evolves to makes electric cars more practical.
Relax wrote:Spacekiwi wrote:Dont forget car crashes.... one crash, and theres thorium spread around. if the dust is inhaled by bystanders and passengers, instant radiation poisoning from inside.
Actually, such a reactor would be VERY safe in a car crash. At worst you would have thorium bits laying around, it melts at 1750C, so it won't be slagging anytime soon like Uranium... assuming one somehow managed to crack open a 1/2"-2" thick pressure vessel which I find beyond implausible beyond bad engineering fail safes outside of a cutting torch that is. Note: Car fires would not come even close to 1750C. Could there be special cases... Uhm well, erm, can't think of any. 1750C is damned close to melting IRON and well, that simply never happens outside of a furnace or the center of an oil well fire, or some very specialized chemical plant fires.
Dust? If inhaled in large doses you are correct, except in your fundamental concept of what would actually be inside said reactor. Is lead dangerous? No, not unless ingested. Can lead be turned into a dust? Yes(belt sander, grinder), in a car crash? No.
It is a METAL in its finished form. Metals do not become powders unless abraded continuously big time, exposed to tremendous pressure(explosions). Once again this is a car crash, not a 2000lb TNT bomb detonation! We are not shooting these pellets at 3000ft/s(1000m/s) creating localized pressure and temperatures far in excess of its metallic bond strength. Only time dust would be a problem would be in the manufacturing of said Thorium,"nuggets" from its raw materials containing particulates.
Now Thoriums by products I am not conversant enough to answer if THOSE could become airborne. The answer is probably YES.
Radiation is not a problem except in monstrous doses. Of which Thorium will not give unless ingested. You can hold it in your hands just fine without problems. Now if you do it 24-7-365 obviously this would be a problem. You can hold U-238 in your hands as well just fine, same goes for plutonium, it is HOW long you hold it that is the problem. Radiation contamination of the environment is. Radiation does not contaminate! Radiation by-products that remain in contact for long periods of time contaminate.
Now, crash criteria keeping its elements apart could be a conundrum as its cooling systems would malfunction and it could melt through its protective vessel slagging the reactor, at which time it will be throwing off radiation like crazy. Of course a simple wedge driven through it by someone in a lead suit would drop its nuclear decay exponentially very quickly. Heat from such a small reactor won't be a problem in that it won't keep someone away from it in order to divide it. Assuming it hadn't already done so during the container vessel breach.
Small reactors major problem is they do not have enough nuclear bombardation to keep the fission process going. Makes for very low temperature and inefficient reactors and therefore easily stopped as well. In major multi MW reactors the mass of the reactor core keeps the process going requiring much more attenuation of nuclear bombardment from surround material to stop it. This is frankly one reason I find a car running on Thorium so implausible. Creating such a small reactor that would actually fission in a meaningful way is well...
NRC data already shows that reactors like MASLWR or NuScale with reactor cores of cross sections of a mere foot in diameter using Uranium/Thorium mixture barely work as is and now we are going to go to an all Thorium reactor? Last I checked, to replace even 3-5% Uranium in fuel rods with Thorium, required somewhere in the neighborhood of, old memory here don't hang me, ok do hang me, twice 100% Thorium rods. So what 5% Uranium rods could do, required 100% Thorium, except twice the volume to keep a nuclear decay rate viable. I could be wrong on the 100% Thor rods. Old Oregon State Nuclear talks info. Oregon state is one of ??? 3 schools, maybe 5, I believe where you can get Nuclear Engineering degree from. The others are New Mexico State and Navy School as I recall.
Anywhoo. Namelessfly would probably have better particulars. Not my area of expertise. But been around a couple who do know. As I recall what they really wanted was Thorium/Uranium/Plutonium breeder reactors. We have enough to power the entire worlds civilization at American power consumption needs for the entire worlds population for the next 10,000 years at a minimum if we built them. Just that "enriched Plutonium, Uranium" "problem".
In other words for the next 10k years we could completely get rid of nearly all use of coal, ng, oil, if we wanted to. We have chosen NOT to.
