The economiics and physics of four schemes of pIutonium recycle in the Calder Hall type reactor are considered. The four possible schemes are: (I) to blend the Pu produced In a run with fresh naturaI U for a subsequeut run; (2) to alloy the Pu with somie diIuent metal and fabricate the alloy Into high heat- transfer elements morc like MIR or PWR-sced type elements and"spike' a subsequent load of fresh natural U elemients with these Pu elemicnts; (3) to recycle half the spent U as well as the Pu; and (4) to thke advantage of the extra reactivity gained fromi the recyeIed Pu to deerease the Iattice spacIng, thereby increasing the conversion ratio with the hope of increasirg the attaInabIe exposure. It was concluded that schcme (1) is the miost economiical. (W.D.M.).