this new type of LMFBR would produce more uranium–233 per unit of consumed plutonium than the type of plutonium-fueled LWR reactor we mentioned above. It would therefore decrease the demands for uranium fuel for LWR types of plants and conserve uranium.

Still another possibility for locally consuming all plutonium produced by reprocessing plants, and for stopping all shipments of nuclear weapon material to power plants, would be to use HTGR's that consume plutonium instead of high-enriched uranium or uranium–233 as fuel; this reactor could produce uranium–233 for use in LWR reactors. It would produce somewhat more uranium–233 per unit of consumed plutonium than a plutonium-fueled LWR-type reactor.

Strictly speaking, we can conceive only a few ways to abolish all shipments of nuclear weapon material to HTGR power plants. One would be to use HTGR reactors only in the system we have just described. Another method would be to build very large power plants to make it economical to locate at the same site as the reactors all parts of the HTGR fuel cycle that involve nuclear weapon materials. A third would be to use uranium of much lower enrichment in the coated fuel particles in HTGR fuel assemblies. The last of these alternatives would probably significantly increase the overall HTGR fuel cycle costs, because it would require diluting the uranium–235 and uranium–233 with four or five times as much uranium–238, while still using relatively large amounts of thorium. Whether this would be worth doing for reasons of nuclear material security is debatable, since fabricated HTGR fuel in its present or contemplated form is not a very effective source of nuclear weapon material. Nuclear weapon materials are dilute in HTGR fuel; they can only be separated from the diluting materials by a complicated set of chemical and physical conversions.