For large PWRs, there are typically three enrichment levels used in assembling a reactor core to produce an even power density. Higher enriched fuel is placed in the outer perimeter zone where neutron flux rates are more dispersed, and the center of the core has lower enriched fuel due to its highest relative intensity of neutron flux. The OPEN100 reactor core, due to its smaller relative diameter, may use less complicated, higher enriched patterns. It is also configure to also run a longer fuel cycle in order to reduce operational costs as well.