modest requirements in the second. Advanced converters on the thorium-uranium cycle (such as the HTGR or LWBR) with fuel recycle have heavy requirements for highly enriched uranium for their initial critical loadings, but after the first loading, they use less separative work than LWR’s.29 Breeder reactors started on plutonium have no separative work requirements and could indeed provide some fissile fuel (above and beyond what is needed to fuel new breeders) to converters.
However, in spite of the uncertainties in future demand for separative work, enrichment is not a bottleneck in nuclear expansion. An enrichment plant takes only as much lead time as a reactor to plan and build, so enrichment capacity can be scheduled to match reactor commitments.*