If aneutronic B11-H fusion is not practical from either a technical or economic standpoint anytime in the near future, then D-T fusion is best served by a fusion/fission hybrid concept, and the Hilion reactor topology is well positioned for this approach.
Any big project should be developed in well thought out, mutually supportive and orchestrated phases. The thorium fusion hybrid should conform to this type of development strategy. The first phase should be the development of a U233 fuel factory. The first market would be existing Light Water Reactors and the new AHTR pebble reactors.
The price for the U233 would be well below the current U235 equivalent price. I think that such a fusion/fission fuel factory is very price competitive and is capable of producing U233 very well below this current $70 lbs yellowcake equivalent. The price of yellow cake has varied from $15 to $137 per pound recently and currently it is about $70 per pound.
http://www.osti.gov/bridge/servlets/pur ... 90-JB2FXN/
The best type of fusion/fission hybrid has a very small zone of fusion preferably a point source. The Hilion reactor has this very important feature and because of the small size of the fusion zone it facilitates an all inclosing blanket with almost perfect closure. Because of the ideal efficiency of its almost perfect liquid blanket envelope, I can see this type of subcritical reactor producing about 5500 kgs of pure U232/U233 per year. Very few neutrons would be wasted. Beryllium in the blanket would almost double the production of the fusion neutron flux. To maximize U233 production, no lithium should be included in the blanket. Tritium would come from the waste flow of its dependent parasitic fission reactors; its customers.
The reactor does not need heat exchangers of turboelectric generators; it can dump the heat produced by fusion (typically 10 megawatts) to the air so a thermal power circuit wound not need to be developed or deployed. Because it is subcritical, it would not need a containment structure either.
If the protactinium
is removed from the liquid fluoride beryllium/thorium blanket through on-line blanket salt reprocessing immediately after its creation, no fission heat would be produced by U233 fission.
Since this hybrid does not need to produce electric power or connect to the grid, this hybrid can operate intermittingly to allow frequent change out of its first wall. Such a diamond pipe can be replaced in a matter of hours. A coating of lithium hydride on the inside of this first wall diamond pipe might greatly reduce alpha particle damage.
I believe that this is the development strategy currently envisioned for the Helion fusion engine development program.
If the U233 can be produced with a 1% or greater U232 content, then no U238 denaturing would be required by IAEA rules. This highly enriched and proliferation proof U232/U233 nuclear fuel would make light water reactors and AHTR very clean and eliminate the waste problem associated with the uranium fuel cycle. This alone would be a big selling point for the thorium/fusion hybrid and get the thorium fuel cycle off at a run.