Mark Massie and Leslie Dewan, as well as David LeBlanc anticipate relatively high conversion ratios in their MSRs, without the use of Thorium. Jorgenson anticipate Thorium cycle conversion, and pays no attention to Plutonium burning.
Here is the Thorcon comment on its fuel:
On a once through basis, ThorCon is not that uranium efficient. Over 8 years, we feed 2,185 kg of U-235 to a 250 MWe module. This equates to 208 tons of natural uranium per full power GW-y. For comparison a standard 1 GW Light Water Reactor (LWR) requires about 250 tons of natural uranium per year. However, at the end of 8 years, the module’s “spent” fuel will contain 1289 kgs of U-233 and U235. ThorCon’s net consumption of fissile is less than half that of a LWR, due to higher thermal efficiency, removal of Xe-135, and U-233 production from thorium. ThorCon “spent” fuel is about 9% U-235 and 4% U-233. This is highly enriched by normal standards. Re-enriching this back to 20% will take about 48 SWU per kg U-235. Currently, an SWU costs $90 and this is likely to drop in the future as the last of the diffusion plants are pushed out of the market. $4000 per kg of U-235 is extremely cheap. Such re-enrichment would cut ThorCon’s uranium requirements in half.