Integral Fast Reactor

russ_watters

I've deleted crackpot and conspiracy theory posts and responses and reopened the thread. Apologies to those who lost time to deleted responses.

Lets keep the thread on point and, more importantly, scientific.

joelupchurch

IFR Question.

I was writing up my ideas for replacing Yucca mountain and I wrote that a fuel reprocessing facility should co-located with the storage facility and also an IFR to handle whatever can't be reprocessed. What exactly would be leftover after that? Would any of it have a long half life? How much waste would we talking about per TWH?

If you want to see what I wrote, use the link and go to section 2.

http://www.anupchurchchrestomathy.com/2009/06/upchurch-american-energy-act.html

signerror

Since there is a one-to-one mass correspondence between fissile material and fission products (minus the tiny fraction of binding energy that is lost), there is a fixed ratio of the mass of fission products to energy generated, for each fissile isotope. For a U-238/Pu-239 closed cycle, it would be about 45 kg/TWh(thermal), where 199 MeV is the energy per fission of a Pu-239 nucleus, and the TWh is of heat produced (not electricity). So for a 50% efficient high-temperature reactor (say), it would 90 kg/TWh(electricity).

So this is the absolute minimum spent fuel waste for any fission reactor. A fast reactor with full reprocessing (like the IFR system) would come close to this.

In an ordinary once-through reactor, there is a lot more waste. For example, the new French EPRs have a (design) burnup of 70 GW-days per ton fuel, which corresponds to spent fuel mass of 595 kg/TWh(thermal) or 1,653 kg/TWh(electric) (so, 26 tons/year). But only a small fraction of this is fission products, corresponding to the same mass fraction which was fissioned (about what, 5%?). The rest is mostly harmless U-238, and a tiny fraction of synthetic actinides created by neutron capture (Pu-239 and beyond). So with full reprocessing and MOX fuel burning (as the French do), the once-through light water reactors produce about the same mass of high-level waste as fast reactors - although since it has a much larger amount of transuranic isotopes, it is much longer-lived.

I hope the experts here will correct me if I've misunderstood something.

joelupchurch

I obviously don't understand. What I read is that 95% of the spent fuel is Uranium or Plutonium and all those isotopes are fissile or fertile and can be reused. Most of the rest is actinides that can be burned in an IFR. It looks to me like the only thing that needs to be disposed of are the actual fission products, but it isn't clear what those products are and how long they are dangerous.

From what I read on the LFTR, it looked like you could get a GWe Year out of 1 ton of Thorium, so the actual waste product would be 1 ton or less. I was hoping to get a similar result with uranium, albeit with more hassle.

From what I read about spent fuel, they amount to about 1 ounce per person per year, so I was hoping to get it down to a couple of grams a year using all the technology available.

signerror

Yes, 1 ton/GWe-yr is about 100 kg/TWh. (There are 10⁴ hours in a year.)

Hundreds of years.



from http://www.nea.fr/html/ndd/reports/2002/nea3109.html

The third bold line is fission products (FPs). The individual examples shown are Strontium-90, Cesium-137, Technetium-99, and Iodine-129.

joelupchurch

Thanks signerror, I like the graph. It looks like most of the fission products are safe in 400-500 years, but there are some long half-life isotopes that need to be separated out and handled differently.

That would mean that each fuel recycling would produce some fission products that need to separated and stored. I guess one ton a year for a GWe electrical plant isn't too bad.

I calculated what a GWe coal plant would put out per year and came out with over 7 megatons of CO₂ and 600 to 700 kilotons of other waste, including 12 tons of thorium and 5 tons of uranium.