Eighteen-year-old Taylor Wilson has designed a compact nuclear reactor that could one day burn waste from old atomic weapons to power anything
from homes and factories to space colonies.
The American teen, who gained fame four years ago after designing a fusion reactor he planned to build in the garage of his family’s home, shared
his latest endeavor at a TED Conference in southern California on Thursday.
Everything seems to point to the fact that Mr Wilson has re-invented small Molten Salt Reactor (that's a bit snarky; I know nothing of what he may
have brought new to the idea, so I'll keep an open mind).
Current technology is for solid fueled reactors in high-pressure vessels, so as to keep the water coolant/heat transfer medium liquid at temps far
above the boiling point; water transfers heat more efficiently there. High pressure is costly, and solid fuel is costly, because it collects fission
products (call it ash) as it "burns", which poisons further fission. After only 2% of the fuel is burned, it has to be reprocessed; currently, that
means thrown away (into the spent fuel pool) and replaced with new fuel.
The MSR defeats these two problems. An MSR operates at low pressures; just enough pressure to move the liquids as needed. It needs some temperature,
enough to melt the fuel, but that's not much above the temps that a water reactor runs at anyway. The fuel, being melted fluorides of the
fissionables (uranium, plutonium and thorium), can be continuously drawn off, stripped of fission products, charged with additional fuel, and fed back
in. Control is maintained by inserted rods, just as it is for the water reactor. In addition, in emergencies or for extended down times, the fuel is
drained into safe storage. There are no fission products to keep it hot like solid fuel, no spent fuel pools, and to restart the tank is heated to
the melting point and the fuel pumped back into the reactor. Voila. You can safely shutdown for St Patty's day, then bring it back online on
Wednesday morning even with hang-overs.
Advantages are that all the fuel is burned; current pool waste is 90% unburned fissionables and activated transuranics, not very radioactive but
scary, because they last forever. The MSR burns all that, and it doesn't care whether the fissionables were mined, milled by Rocky Flats/Pantex, or
drawn dripping from a cooling pool, or any combination. All are treated equally. There are also disadvantages, but the chief one is that the
technology is unexplored as compared to solid fuel reactors.
Other small buried local reactors can be easily googled; here is one:
quoted from phage:
A mini sodium cooled reactor on every block. Great idea.
Um. What happens to all the spent fuel?
quoted from purplemer:
We put them in a rocket and fire them at the sun... That should work....maybe
No. The waste is only about 10% of that of current day reactors. It has a much short decay time (300 years for the bulk of it), and some of the
products have commercial uses, like Pu-238. NASA loves the stuff for Radioisotope Thermal Generators (like on Curiosity), and it's getting rare.
Today's waste is tomorrow's diamonds.
quoted from phage:
The products of nuclear fission include 235U and 239PU. Both radioactive but not fissionable.
Once the amount of fissionable fuel falls below critical mass the chain reaction stops and no power is produced. But there is still radioactive
Normally inert materials (including the body of the reactor itself) become radioactive through neutron bombardment.
Actually, Pu-239 is fissionable plutonium (the common kind, used in almost all bombs). U-235 is fissionable "enriched" uranium, the other major bomb
component. Pu-239 is "sorta" a waste product, the result of U-238 (common uranium, aka depleted uranium) bombarded by neutrons, as in a reactor.
That is, in fact, how plutonium is manufactured at Hanford.
There is radioactivity left, but it is in the fission products like I-131, K-40, Cs-137 and other nasties. In an MSR they are removed incrementally,
continuously, and never build up. It is nasty because it has high intensity, but therefore low half-life, therefore it decays away to background
within about 300 years.
The thing that stops normal reactors is poisoning by fission products, not the consumption of the available fuel.
Your last statement about neutron activation of the reactor is certainly true.
quoted from intrptr:
Haven't we had enough of that? For a 1000 half lives?