The objective of this presentation is to: (1) present the physical motivation for fusion-fission hybrids, (2) outline design considerations for hybrid blankets, and (3) discuss the nuclear performance potential of hybrid blankets.

The sensitivities of district heating costs to various design parameters are explored. Some recent studies evaluating the economics of district heating are briefly summarized. The bases and methods for the cost and design sensitivity studies are outlined. Cost and design relationships are examined. These relationships are developed as part of a design study for a city with a population of 175,000. Use of a specific city as a basis for these studies shows the importance of site specific factors in the development of the best district heating design for the city. The problems of utilizing the delivered water are briefly reviewed. Some alternatives system designs are compared in terms of economics, energy efficiency, and their potential for widespread application. (MHR)