November 29, 2009
Better Uranium Fuel Burn In Advanced Gas Reactor
In a research program for next generation Advanced Gas Reactor (AGR), uranium fuel burns far more efficiently than in existing light water reactors.
WASHINGTON, D.C. — Idaho National Laboratory (INL) scientists have set a new world record with next-generation particle fuel for use in high temperature gas reactors (HTGRs).
The Advanced Gas Reactor (AGR) Fuel Program, initiated by the Department of Energy in 2002, used INL's unique Advanced Test Reactor (ATR) in a nearly three-year experiment to subject more than 300,000 nuclear fuel particles to an intense neutron field and temperatures around 1,250 degrees Celsius.
INL researchers say the fuel experiment set the record for particle fuel by consuming approximately 19 percent of its low-enriched uranium — more than double the previous record set by similar experiments run by German scientists in the 1980s and more than three times that achieved by current light water reactor (LWR) fuel. Additionally, none of the fuel particles experienced failure since entering the extreme neutron irradiation test environment of the ATR in December 2006.
Higher fuel burn efficiency offers a few benefits. First off, more complete burn reduces the waste disposal problem. If 3 times as much of the uranium gets burned then the amount of waste produced goes down by a factor of 3 per amount of electricity produced - all else equal. Plus, this reduces cost of uranium since each amount of uranium produces much more electricity. Plus, if the fuel burns at the same rate then refueling happens less often and therefore reactors operate for longer between refuelings. This raises productivity and cuts costs.
Technological advances that cut the cost of nuclear power are good because if nuclear power costs fall below coal electric power costs then nuclear would gradually displace coal and we'd live in a less polluted and less environmentally damaged world.
High temperature reactors incorporate the uranium into particles embedded in substantial amounts of carbon, so the total mass to be disposed may actually be higher than in LWRs, where the moderator is entirely separate.
Separating the uranium carbide/nitride particles from the carbon would reduce the mass of the high level waste, but this also breaks the seal that prevents the mobilization of fission products and is, in effect, a simple kind of reprocessing. The carbon that comes out would likely still be contaminated and would still have to be disposed of as lower level radioactive waste.
"If 3 times as much of the uranium gets burned then the amount of waste produced goes down by a factor of 3 per amount of electricity produced - all else equal."
Only if you go along with the anti-nuke scam of labeling mostly un'burnt' fuel as "waste". Which I refuse to do.
Only if you go along with the anti-nuke scam of labeling mostly un'burnt' fuel as "waste"
Reprocessing is economically absurd at current uranium prices, so right now it is indeed waste. Fortunately, storing spent fuel above ground in shielded passively air-cooled casks is not expensive or complicated, so the waste can be preserved for the time, perhaps generations from now, when it may be economical to reprocess it.
Reprocessing would radically reduce the amount of material of concern, and would be one way to deal with a shortage of uranium; the 1% U-235 in spent LWR fuel could be used directly in CANDU reactors, allowing the CANDU fuel stream to be used in LWRs instead. A uranium exchange with Canada could fuel perhaps 15 GW of LWR capacity in the USA for quite a few years.
HTGR fuel doesn't allow this. According to this IAEA document, the fuel in a TRISO element is distributed through about the inner 5 cm diameter of a 6 cm spherical fuel element. This means that there isn't much to be gained by separating spent fuel elements unless the individual fuel particles can be removed. Perhaps the outer coating of each element could be sandblasted off and the graphite removed by oxidation to leave the SiC particles, but that's going to be mighty expensive. It's far easier to handle LWR fuel.
If we are concerned about fuel economy, LFTR and other MSR designs are much better than pebble-bed reactors. However, there's no repeat business in fuel fabrication for MSRs.
You know that the oil that we use in our civilization was a waste extracted from salt wells .Since the 1840s, salt wells were becoming fouled with petroleum.At first, they simply dumped the useless oil into the nearby Pennsylvania Main Line Canal, but later they began experimenting with several distillates of the crude oil .The useless waste of today could be the energy generator of tomorrow.