Energy From Thorium Discussion Forum

Maybe you answered this question elsewhere, but I didn't still understand how fast chloride and thermal fluoride reactors should mutually work. For example, I understood that a fast chlorides can burn up LWR transuranics "waste" and produce enough uranium 233 in its blanket to start other reactors, but like every reprocessing, even in a clever salt liquid form, is not 100% perfect, so we'd always have some other transuranics leaking out. On the other hand, a LFTR (or every other fluoride reactor in any different configuration) even started up with uranium 233 is going to produce some TRUs waste, again due to the lower than 100% efficiency of fuel reprocessing, so what about these two possible flows of TRUs waste, granted that one of positive feature of MSR is the reduction, is not almost removal, of the problem of long life/high toxicity of nuclear waste (transuranics, indeed, in particular).

There is indeed no 100% efficiency in reprocessing technologies. The closer you want to get to 100% the more complex and expensive it gets.

In a MCFR (Molten Chloride Fast Reactor) you will generate fission products, higher actinides, 36Cl and some activated structure material. Most probably it makes sense to target the economic optimum of the reprocessing process.

you can reuse the used carrier salt as NaCl
You can reuse the actinides as a fast reactor fissions all fissionable actinides.
You can put the CsCl and the SrCl2 (fission products) back in the reactor as their nuclear, thermodynamic and chemical properties are not bad.
You can recycle some of the precious metal fission products as Tc, Rh, Ru, Ag that is not plated out in the reactor.
You might use some radioactive fission products for medicine and other purposes.

At the end you will have indeed some contaminated waste.

Please be aware that all technologies used for electricity generation generate more or less waste. This includes solar and wind. In case of nuclear it is made a big issue in case of solar it is never mentioned.

Indeed, let's focus on transuranics (the remaining stuff is quite easy to store/process), what is the best option to minimize it and produce energy at the same time ? For example, considering that a fluoride one GWe thorium reactor using one tonn of thorium per year (or one tonn of U-233) could produce, say, 2 kg of TRU per year due to the inefficiency of reprocessing, does it make sense to burn them in a chloride fast reactor (that at the same time can produce some uranium 233) ? Yes, obviously the final target should be to minimize transuranics waste to, say, a few hundreds grams per year per GWe reactor at max, not to completely eliminate them...

I am glad a combination of thermal and fast reactors is being considered.
A thermal breeder was built at Shippingport but not put into production. It could be done as a near breeder or breeder but producing U-233. A candu using heavy water moderator and light water coolant may be more economical. With no new hardware development required, the cost could be kept down. With outer tubes used as a blanket as suggested by Radkowski, it could even be a breeder.
MSR could be developed as an un-moderated TRU burner.

MCFR and DMSR could work quite well together. If the MCFR presents its breeding gain as denatured U233 which can be the topup fuel needed by MCFR and given that U233 has superior properties as a thermal spectrum fuel I think, but cannot confirm that buildup of U238 in DMSR will be slower than for the case where topup fuel is denatured U235.

The used carrier salt can only be recycled.
Cs and Sr fission products are so radioactive that they are best used as RTG fuel for terrestrial work.
Precious metal fission products can only be used as radioactive sources. May be as catalysts in some cases and circumstances.
There will always be some wastes to be buried. It could be small enough for deep boreholes.