Investigations of the requirements for seawater desalination plants with a performance in the range from 10 000 to 80 000 m3 distillate per day heated by a nuclear reactor were conducted. The desalination plants consist of Multi-Stage-Flash (MSF) evaporators of proven design. The reactor concept is similar to the integrated pressurized water reactor (IPWR) of the nuclear ship OTTO HAHN. The design study shows that IPWR systems have specific advantages compared to other reactor types when they are adapted to single-purpose plants for water desalination or to dual-purpose plants for water desalination and electrical power generation. The calculated costs of the dual-purpose plant show the advantages of the larger unit size and the reduction in water production costs through the sale of electrical power and also gives some flexibility in the pricing of the joint products.