The environmental impact resulting from the release of radioactive material during reprocessing and refabrication of spent LMFBR advanced fuels was compared with that from similar treatment of reference oxide fuel. Candidate advanced fuels include carbide ((U,Pu)C) in addition to nitride ((U,Pu)N) with selected concentrations of /sup 15/N. Several techniques for preparing enriched /sup 15/N were reviewed and estimates were made of the cost of preparing nitrogen enriched to greater than 99 percent by each method. Core neutronics, fuel management, and designs appropriate for each fuel were used with the ORIGEN code to calculate the compositions of spent core and blanket fuel. The mass of fuel recycled annually was that providing 50 GW(e)-years of energy at the burnup attained by each fuel. Confinement factors for each isotope were identified for reprocessing and refabrication operations and were used to calculate source terms describing isotopic release rates. These source terms were used in the AIRDOS-II code to estimate the 50-year dose to the maximally exposed individual and to both the local and world populations. Total body dose commitments to the maximally exposed individual for oxide and carbide fuels are about 2.8 millirem, while nitride fuel would result in a range of 59 to 3.4 millirem as the /sup 14/N content in fresh fuel is varied from 99.64 percent to zero
