This study analyzes from an availability point of view the economics of the different operating modes of a nuclear plant supplying a district heating system. Unit thermal cost is calculated at different extraction temperatures for each mode. A comparison of these costs showed that the most economic extraction for district heating should be done at the lowest possible temperature, and it is most beneficial to operate the nuclear plant on a monthly averaged load following scheme and rely on the inherent storage of the system to cover peaks. Three different storage systems have economically been analyzed and they are incorporated in the study for long term storage only. Although long term storage is beneficial from energy utilization point .of view, its high capital cost and the relatively low cost of nuclear energy placed it as the most expensive mode of operation. Water as a supplying medium for the district heating- system is heated in one stage for the different modes of operation. Two stage heating is only considered for one operating mode since similar conclusions can be drawn for two stage as those obtained from one stage heating.