One of two project reports: The other part is designated Part B: On-Campus Project / <p> Computer studies are made of a CANDU-PHW reactor core containing an annulus of enriched uranium around a central zone of natural uranium. For hybrid cores of this type with a maximum radial form factor, the uranium requirements, fuel costs, stability, and power peaking upon refuelling are investigated. It is found that these hybrid cores offer potential savings of 10% to 20% in fuel costs and uranium utilization compared to the present CANDU-PHW core, and are only slightly less stable. However, power peaking upon refuelling is a problem with these cores.</p> / Thesis / Master of Engineering (ME)