Excellent concept Cyril ! ....I like it very much !Cyril R wrote:...the idea of a molten salt cooled reactor with traditional fuel rods can really work. Advantage is that metal fuels can be used with a very high HM loading compared to TRISO, and potentially much cheaper fuel fabrication, while getting similar high fuel failure temperatures that the TRISO have as major advantage. Also with no graphite to cause positive coolant void other coolants become available such as NaF-BeF2 with a melting point of just 340 degrees Celcius, a lower vicosity and lower cost/better availability compared to FLiBe.
This would be a much higher power density core compared to the AHTR - probably more similar to PWRs or higher. And lots of fast fission in the thorium-plutonium thick metal fuel.
I suspect that the inside of the SiC fuel pins might need some sort of thin buffer layer to absorb the metallic fuel's thermal and radiation/FP-induced expansion, while efficiently transmitting heat to the SiC sheath -- since the material likely can't strain (expand) with the fuel without cracking, as much as an ordinary Zr or SS sheath would be able to (as in the case of the Integral Fast Reactor - IFR).
This buffer layer approach is used in the TRISO fuel kernels of the PB-AHTR design -- where the UO2 fuel itslf is likely more stable against expansion than U-metal.
Venting of the fuel pins only reduces internal pressure due to gaseous fission product (FP) buidup, but it doesn't do much to reduce the fuel expansion.
Also, if you’re going to be using Th in this thing, then you’ll probably need a good deal of out-of-core fuel buffering, to allow for Pa233 decay.
This frequent fuel shuffling might be difficult, if you have vented fuel pins connected to off-gas piping & valves….