As I previously mentioned, I was involved in a proposal to the Advanced Research Projects Agency-Energy (ARPA-E) on an investigation in using liquid-halide reactors (both chloride and fluoride) along with salt-based reprocessing techniques to investigate how to address our issues surrounding spent nuclear fuel–often erroneously called “nuclear waste”.
In a nutshell, we proposed to fluorinate the uranium oxide spent fuel, turning the constituents of the fuel from oxides to fluorides.
Uranium, comprising more than 95% of the fuel, would be removed by further fluorination to uranium hexafluoride (UF6). UF6 is the input material to uranium enrichment processes. Thus, 95% of spent nuclear fuel could be sent to an enrichment plant in this process for additional use. Its isotopic composition would be fairly similar to natural uranium, with a little more U-235 and a lot more U-236.
The fission products would be separated for decay, since they decay fairly quickly to stable nuclides. The ones that were already stable could be partitioned and sold.
The transuranic nuclides like neptunium, plutonium, americium, and curium are the things that give you most of the headaches from a long-term disposal or fuel management approach. This is where most of the effort in the proposal would have gone–into a strategy for burning these up. My favored approach is to put them in a fast-spectrum liquid-chloride reactor and burn them up. If the chloride reactor was surrounded by a thorium blanket we could make new uranium-233 fuel for LFTRs, and the LFTRs wouldn’t produce these transuranics in the first place.
So, here’s the proposal. Mind you, it isn’t the “full” proposal, but rather an 8-page “teaser” that was designed to attract ARPA-E’s interest and keep us from having to go to the trouble of making a full proposal if they weren’t interested. For that, I appreciate their strategy of letting us know early if they didn’t think we would be making an interesting proposal to them.