I am interested in lowering the cost of nuclear reactors through the use of novel reactor designs, particularly fast reactor designs. The Integral Fast Reactor (“IFR”) is a good starting point for a discussion since it was a real reactor with a long operating history. A few features of the IFR seem to have the potential for greatly reduced cost: 1) Core power density of the IFR was about 10x as great as a conventional light water reactor (“LWR”) 2) The coolant, liquid sodium, was kept at atmospheric pressure and did not go through a phase change 3) The IFR was capable of a much higher breeding ratio and higher fuel burnup than LFR’s High power density means a small reactor core and atmospheric pressure/ no phase change greatly reduces the size of the containment structure. Ideally this would allow for a reactor small enough to be factory built and transported by barge. Although they are still only concepts, the Toshiba 4s Reactor and the “Traveling Wave Reactor” share these ideas. Higher fuel burnup allows for more efficient use of uranium and potentially for simpler design. The IFR was designed to allow for fuel reprocessing which greatly complicated its overall design. (Moving fuel in and out, keeping spent fuel in the sodium bath while it cooled, transport and handling of highly radioactive spent fuel, etc.) A very high burnup reactor would eliminate much of this complexity (lifetime fuelling). One of the Physics Forum posters, Vanesch, wrote the following: “To me the most logical design of a breeder is a rather homogeneous mix of "initial fuel" and of fertile material, such that the breeding ratio is close to 1: the consumed initial fuel is then replaced by newly bred fuel. The problem is of course the build-up of fission products and the diminuation of U-238 concentration. For the neutron balance, the fission products will eat some neutrons, on the other hand the U-238 will eat less of it, so the neutron balance must remain close to the same. Of course you can't burn up everything, as you need a certain amount of U-238 for passive safety (Doppler effect) and in any case your fuel elements will be damaged after a while (first barrier).” This raises two important problems with the Very High Burnup Reactor (“VHBR”) – safety and the need for new materials to handle extended periods of high flux. In terms of safety – reactivity control is a concern. The reactor would be running on Pu 239, which has relatively few delayed neutrons. Material evaluation of certain forms of steel and of the fuel itself had begun at the IFR. U-Pu-Zr alloys and different forms of steel tested. At least some of this work has been completed. Any thoughts?